Halcyon

This Addon is and always will be free. If you paid for this, you were scammed. Please demand your money back and report the seller.

A from-scratch render engine for Blender, built for the looks Cycles and EEVEE cannot give you: the 3D of every era before physically-based rendering, and 2D — hand-drawn, painted, filmed — down to the wire.

Not a filter over a modern render. Halcyon is its own scanline z-buffer rasteriser with optional ray tracing, the reflectance models the old packages actually shipped, real framebuffer quantisation, a genuine GLSL/HLSL compiler for coded-shader nodes, and a complete GPU port of all three stages that is held to the CPU picture pixel for pixel — same frame, same numbers, on either device, in any band, on any worker. Everything is Python and NumPy, nothing compiled, and the whole engine runs headless without Blender for its 5,000-check test suite.

Three roads, one engine.

The eras. Ninety render presets, each what its target actually did — Infini-D, Ray Dream, 3D Studio R4 and MAX, trueSpace, LightWave, Imagine, POV-Ray, Bryce, Softimage, Alias, RenderMan; VGA, EGA, CGA, the Mac 1-bit and 8-bit palettes, Amiga OCS/AGA/HAM, Atari ST, PC-98, X68000; PlayStation, Saturn, N64, Voodoo, Dreamcast; NTSC, VHS, the early web. Shading rates (Gouraud and Flat as rates, not models), affine texture warp, vertex snapping, three-point filtering, error-diffused and ordered dither, real palettes, HAM fringing, interlace, JPEG's DCT — the mechanism, never a blur.
The libraries. Your Blender 2.79 files open with their Blender Internal materials intact — a plain File ▸ Append brings a scene saved twenty years ago in looking as it did: shader pairs, ramps, all eighteen texture slots on a ported BI texture engine, lamps at their true 2.79 energies, the old world as sky and fog. The Bryce 1995 material library, decoded from the original .mat files byte by byte, sits on the Pre-Made shelf with the numbers Bryce saved in December 1995. And 3ds Max's material and map library — the Standard material's eight shaders, the Raytrace material, Blend / Double Sided / Top-Bottom / Shellac / Composite, the maps, utilities and coordinate rollouts, a shelf of thirty-five nodes — runs on Max's own algorithms, reimplemented on Halcyon's own tables (no Autodesk code or data ships), with a 3ds Max 2012 render preset.
The 2D road. A Cartoon Shader (paint, not light: the Golden Age, UPA, Xerox-line, Saturday-morning, 90s feature, wartime noir and modern flat eras) and an Anime Shader (kage tones, the hair shine, the airbrush, a six-decade Style menu, and compatibility modes that decode real game texture conventions — ArcSys, Genshin, ZZZ); an ink pass drawn from the shared G-buffer — clean, brush and pencil lines that taper, roughen, drift, skip and boil, the inker's weight by the light, Arc System Works' vertex-colour line control; 2D media converters that turn the lit cel into hatching, pencil scribble, stipple, charcoal, ink wash, paint strokes and paper; painted backdrops and painted grounds laid in brush strokes; and the film the cel went through — the three-strip camera's records and filters, the timed print curve, impure dyes, dye-transfer registration, the silver key, then grain by size and clump, dust on the cel, the negative and the print, hairs in the gate, scratches, cue marks, gate weave, flicker, frames held on twos and threes.

At a glance: 32 shading models · 243 node types evaluated (every shader node Blender 5.x offers, plus Halcyon's own 137) · 90 render presets in seven categories · 140 resolution presets · 113 Pre-Made material templates in fourteen families · nine sky modes, 303 skies, 48 waters, nine infinite grounds · real volumes (eight scattering models, mesh containers, voxels) · 291 render settings, every one proven to change what it claims · a 5,373-check suite that runs without Blender · about 99,000 lines of Python and NumPy (142,000 with the tests), no compiled dependencies.

Install

Download the latest halcyon-*.zip from Releases — take the zip, not the source archive.

Blender 5.1+ (extension): Edit ▸ Preferences ▸ Get Extensions ▸ ▾ ▸ Install from Disk… and pick the zip.

Any version (legacy add-on): Edit ▸ Preferences ▸ Add-ons ▸ Install…, pick the zip, then tick Halcyon Render Engine.

Then set Render Properties ▸ Render Engine ▸ Halcyon. If Blender's view transform is not Standard, the Display panel will say so and offer a button to fix it — Halcyon outputs display-referred pixels, so AgX or Filmic on top double-transforms them. Open the Halcyon Presets panel and load one — VGA Mode 13h or PlayStation show the character of the engine fastest.

Requires Blender 5.1 or newer, and only NumPy, which Blender already ships. No compiled dependencies, nothing to build.

Running the tests

The renderer and the shader compiler import nothing from bpy, so the whole suite runs on a plain Python with NumPy — no Blender, no display:

git clone <this repo> halcyon
python -m halcyon.tests.run_all

That is what CI runs, on Linux, Windows and macOS.

Reporting a problem

Turn on Developer Options in Preferences ▸ Add-ons ▸ Halcyon, then use Run Self Test in the Debug panel. It copies a report to your clipboard covering your GPU, the shaders compiled on your own driver, a 116-row feature-by-feature comparison of the GPU picture against the CPU's, per-stage frame timings and thread scaling. Nearly every bug in this engine's history was diagnosed from that output; almost none from a description alone.

Blender 2.79 appending — the headline feature

Blender removed the Internal engine in 2.80, and every .blend saved before then carries materials modern Blender silently drops. Halcyon brings them back, two ways:

File ▸ Import ▸ Legacy Scene (.blend) appends a 2.79-or-earlier file through Blender's own loader — constraints, custom normals, modifiers, vertex groups, parenting, animation and every object type arrive exactly as File ▸ Append would bring them — while Halcyon reads the same file directly for everything that loader drops:

Blender Internal materials, rebuilt one to one. Diffuse and specular shader pairs (all the Internal menu's models), hardness, ramps with their inputs, blends and factors, mirror with Fresnel, transparency in Z and raytrace modes, emit, ambient, translucency, Shadeless, Shadows Only, ray-bias and shadow-bias terminator fixes, object colour, light groups — every panel field accounted for, transcribed against the 2.79 source code rather than approximated from memory.
All eighteen texture slots per material, with their mappings, projections, influences and blend modes — and the procedural textures arrive on the BI Texture node, a port of the original texture engine: Clouds, Wood, Marble, Magic, Blend, Stucci, Noise, Musgrave, Voronoi and Distorted Noise over the original noise bases and lookup tables, colorbands included, verified CPU-against-GPU in the suite. Packed images unpack and travel; image sequences keep their settings.
Lamps with their real energies. 2.79's lamp math — distance falloffs, sphere clipping, spot blends in cosine space, the quadratic sliders — is applied from the file's own DNA, so a scene lit for Internal is not a washed-out or pitch-black surprise. Ray and buffer shadows both convert, bias and softness included; pre-2.70 spot sizes convert their degrees.
The world comes along: horizon and zenith as a Halcyon gradient sky, ambient into the lighting, mist as fog with its falloff, exposure and range, and the file's own colour-management settings mapped onto the engine's pipeline (a 2.4x-era file renders bytes-in bytes-out, exactly as it did).
The file's own framing: render size, percentage, transparent film, and the saved "Selected Objects Only" state are honoured; hidden objects can come along or stay home, by checkbox.

Plain File ▸ Append works too. A watcher recognises a pre-2.80 file the moment Blender finishes appending from it and fixes the lamps automatically — no special import path required, and a Fix Appended Lamps button in the Lighting panel covers anything appended before Halcyon was enabled. Every import writes a full log to a text datablock, so what was converted — and anything that could not be — is named, not guessed at.

What it does

32 shading models, each implemented from its published formulation rather than approximated:

Lambert · Gouraud · Flat · Phong · Blinn-Phong · Blinn · Cook-Torrance · Oren-Nayar · Minnaert · Ward · Anisotropic · Metal · Strauss · Multi-Layer · Toon · Translucent · Constant · Wireframe · Anime/Cel · Cartoon · Oren-Nayar-Blinn · the Blender Internal matrix (every 2.79 diffuse/specular pair) · and 3ds Max's own eight — Phong, Blinn, Metal, Anisotropic, Multi-Layer, Oren-Nayar-Blinn, Strauss, Translucent — on Max's light loops

Gouraud and Flat are treated as shading rates, not reflectance models, because that is what they are. Selecting Gouraud on a material evaluates its lighting once per vertex and interpolates the colour across the triangle; selecting Flat evaluates once per face. That is where the banding and the faceting genuinely come from, and it is why they look right instead of merely blurry.

243 node types are evaluated — 102 of Blender's own, audited against its full surface-node registry, and the audit came back clean: every shader node Blender 5.x offers has an evaluator except Freestyle's stroke UV, which has no meaning outside Freestyle. That includes the full Principled BSDF, node groups (recursively), muted nodes, reroutes, all the texture and colour nodes, and every Math and Vector Math operation. Nodes the engine doesn't know pass their first matching input through and are reported as a warning rather than failing the render. A second audit stands behind the first: every property a Halcyon node declares must reach the renderer — a node whose dial changes nothing fails the build with the dial named.

The master shader carries the era's whole bag of tricks on one node — Fresnel, rim light, sheen, matcap, reflection tint, edge opacity, backface override, vertex colour mix — all applied outside the reflectance model so they behave the same on every one. Bump Height takes any greyscale texture and bumps it straight into the shading normal: behind the scenes it becomes a real Bump node between the texture and the Normal chain, so it renders identically on both devices by construction. The Material Properties tab drives the same material with plain sliders when Override is on — override withholds the node tree at export, so what the panel shows is exactly what renders.

New materials created while Halcyon is the active engine are born as master shader materials — the panel's New button builds one directly, and a strictly-guarded watcher converts factory-fresh default materials (exactly the two untouched default nodes; anything a person has edited is never touched).

The Anime Shader (1.62) is a second master node, built for the 2000s-2020s 3D-anime look rather than the 1990s one: N·L wrapped and cut into two or three tone bands whose shadow COLOURS multiply the base — a shadow is a colour, never a darkness — with a stepped cel highlight, rim, matcap, line art, per-material Light Response, and an emission road. Its Compatibility mode decodes real game texture conventions: the ArcSys ILM/SSS maps of the Guilty Gear Xrd lineage and Dragon Ball FighterZ (channel semantics from the published shader recreations of the GDC 2015 pipeline), the HoYo character lightmaps of Genshin Impact (decode taken from the PrimoToon shader source) and Zenless Zone Zero (per its modding guides), and the Dragon Ball action games — Kakarot, Sparking! Zero — served by the ArcSys-lineage decode their looks descend from, with their tooltips saying exactly that rather than inventing channel dumps nobody has published. Plug a game's own ILM or lightmap into Game Texture and the channels mean what they meant at home; every mode shades identically on CPU and GPU, per-pixel texture decode included. Vertex-colour AO (the Xrd painters' convention) and alpha-is-emission (the HoYo one) ride checkboxes. The ramp road (1.65): link a texture — the game's own ramp, a ColorRamp, any chain — into Shadow Ramp and the tone bands come from the ramp itself, baked once into a LUT the lamp loop samples by the light term; shadow side, transition and lit side are all painted, exactly the games' convention. Ramp Row picks the row of a multi-row ramp, and under GENSHIN the Game Texture's alpha — the material id, exactly where the game keeps it — picks the row automatically: the per-row character ramps travel at last. Both devices sample the same baked texels.

The Max study, second reading (1.86) — the field supplied Max 2012's own map and shader algorithms (the MetaSL/HLSL ports that ship with Max), and the 3DS Max shelf now runs them step for step on Halcyon's own hash-derived tables — no Autodesk code or data ships. Every 3D map rides Max's 512-lattice gradient noise (Perlin's 1989 noise as max_texutil carries it, 3D and 4D with Phase as time); Cellular is Max's Poisson Worley (point counts per cell, squared distances, the fractal sum by lacunarity, a Variation control and a Cell ID output); Dent, Planet and Wood ride Max's 20-periodic linear noise; Smoke, Speckle, Splat, Stucco, Swirl, Checker (Max's two checks per tile, the integrated Soften), Tiles (Max's mortar geometry, Line Shift, Random Shift, Color Variance) and Waves (wave sets seeded by the C runtime's rand(), so the same seed places the same sets) follow their originals; five maps are new — Marble, Perlin Marble (the thirteen-knot spline), Wood, Dent and Gradient Ramp (Max's eleven gradient shapes on a three-flag ramp). Falloff gains Max's exact Fresnel equation, Max's Distance Blend order (Side near, Front far) with Extrapolate, and Shadow / Light (the Light Meter's road, CPU-only by name); Output gains Output Amount and Alpha From RGB in Max's order, Mask scales the alpha too. Sizes are Max's Size (coordinate over Size) at Max's own defaults over 100. The master shader gains the eight Standard shaders as new models — Phong, Blinn, Metal, Anisotropic, Multi-Layer (with its second highlight's own sockets), Oren-Nayar-Blinn (Max's Oren-Nayar with the interreflection term), Strauss and Translucent (with a Translucent Color), each labelled "(3ds Max)" — on Max's own light loops, on both devices. Every twin is held to its NumPy original at the bit where the maths allows, and the GLSL simulator itself gained a float32 discipline on the way (a Python literal in a vector constructor used to promote a lane to float64). Every road that did not change holds bitwise against 1.85.0. Then, on the field's second ask, Max's own material panels as nodes: Standard (3ds Max) — the Standard material 1:1 with its rollouts (Wire, Faceted, the eight-shader menu, Ambient/Diffuse/Specular with the lock, Self-Illumination as Max's own lerp or as a colour, Opacity, Specular Level, Glossiness, Soften, each shader's extras, Opacity Falloff, IOR, the Diffuse and Bump map amounts, Reflection) — and Raytrace (3ds Max) (Reflect, Luminosity and Transparency as colours, the way Max reads them), both showing Max's labels and units over the master's identifiers so the bake machinery treats them exactly as the master (a linked percentage refuses the GPU by name rather than shading raw); the node at Blinn renders bitwise the master at MAX_BLINN. The shelf's last maps on Max's own algorithms: Gradient (with its noise and sramp threshold), the Composite map (Max's twenty-five blend modes and its "over"), Color Correction (Max's HSL, Standard and Advanced lightness), Vertex Color, and the XYZ Coordinates rollout in Max's matrix order — and, so Object XYZ could shade on both devices, the object frame now reaches the GPU (the Texture Coordinate node's Object output had been answering world position there, a silent split on any moved object). A 3ds Max 2012, Default Scanline render preset at 2012's own defaults, gamma off as it shipped. 35 nodes on the shelf.

The Max study (1.85) — 3ds Max's material and map library, from the 2012 reference rollout by rollout, under a 3DS Max submenu of the Halcyon Add menu (which now leads the Add menu instead of trailing it). Materials: Blend (two materials by a Mix Amount or a mask, with the mixing curve's Lower/Upper zone), Double Sided (a Facing and a Back material, Translucency letting each show through), Top/Bottom (by the normal's up, with Position and Blend), Shellac (the second material's colour added by Color Blend) and Composite (a base and four layers, each Additive or Mix by its Amount). Textures: Noise (Regular/Fractal/Turbulence with fractional Levels, Low/High thresholds, Phase), Cellular (Circular or Chips, Spread, Fractal iterations, Roughness, the Low/Mid/High cut into Cell and two Division colours), Smoke, Speckle, Splat, Stucco, Swirl (Twist, Intensity, Amount, Constant Detail, Center, Contrast, seed), Planet (three water and five land colours by depth and height, Ocean %, Island Factor, Blend), Waves (wave sets on a sphere or circle, wavelength range, Amplitude, Phase), Checker (with Soften) and Tiles (Stack, Running, English and Flemish bonds, counts, gaps, Holes, Fade Variance) and Falloff (Perpendicular/Parallel, Towards/Away, Fresnel, Distance Blend, against the view or a world axis). Utilities: Mix with the mixing curve, RGB Tint, Output (Level, Offset, Invert, Clamp), Mask and RGB Multiply. Vectors: the Coordinates rollout (map channel, object or world XYZ, screen; Offset, Tiling, Mirror, W Angle). Every map's GLSL twin is held to its NumPy original point by point and every node to the CPU frame on the deferred pass. The master shader gains Max's Oren-Nayar-Blinn model and a Faceted flag, and the Cartoon Era menu gains Ink 'n Paint at Max's own defaults (with a shelf recipe). Housekeeping the field asked for: the texture shelf is categorised (Noise & Fractal; Stone, Wood & Organic; Tiles & Fabric; Sky, Water & Effects; 2D Media), Matcap Coordinates lives in the Vector family and the BI Texture in the Blender Internal family. One engine change came out of the study: an Add Shader of two Halcyon masters now SUMS their colours on the CPU as the GPU always did (it averaged before — a silent divergence the Shellac road exposed); every mix holds bitwise.

The hair pass, the film scans and the tooltips (1.84) — three finishing fronts. The hair highlight grows up: the angel ring's edge takes a Shape menu (the smooth wave it always had, plus the zigzag "W" highlight of 90s TV, the scalloped run of petals, and the hard stepped notch of the digital era), a Hair Shine Angle that turns the wave's phase around the head (stagger the notches on a second character with nothing else changed), a Hair Shine Follow that lets the band ride up and down with the key light's height — 0 is the painted band that ignores lighting, exactly as before; it listens to the scene key's elevation and stays put under a purely positional lamp — and a Hair Shine Second Color so the echo band below can carry its own tint rather than a copy. The Cartoon master takes the whole hair bag — all eleven sockets, the same code — because the American tradition airbrushed hair too. Both devices render every new road identically; every knob at its default is bitwise the 1.83.0 engine. The resolution shelf gains 24 formats, including a whole Film Scans group (35 mm Full Aperture and Academy in 2K and 4K, Super 16, and the CinemaScope 2K scan whose 2:1 anamorphic pixels un-squeeze on the way out — render spherical, deliver scope), the missing home computers (Amstrad CPC, VIC-20, the Atari ST's three modes, Sharp X68000, NEC PC-88), the handheld and console gaps (TurboGrafx-16, 3DO, Game Gear, Lynx, WonderSwan), the laptop panels every deck actually shipped on (1366×768, 1600×900, XGA+, WQXGA, QSXGA) and the modern ultrawides (DQHD, 5K2K, the 4:5 social portrait). And every option in the add-on now explains itself: every socket on the three master shaders, every node property, every enum entry, every render, world, material and light setting carries a written tooltip — applied to old files' nodes the moment they load, and enforced by the suite so a thin tooltip is a failing test from here on.

The preset expansion (1.83) — more of both traditions, on one menu each. The Anime Shader gains a Style menu (the Cartoon Era menu's idea for the anime decades): 80s Film Feature (one restrained warm kage under the optical printer's softness, matte paint, a wide gentle hair sheen, a breath of airbrush), 80s TV (the hard cool-violet tone and the waving angel-ring), 80s OVA (the video market's glamour: two kage tones, a Fresnel rim, a double hair shine, airbrush both sides), 90s TV (cooler, more saturated, a bolder simpler hair band), 2000s Digital (dead-hard bands, the early RGB palettes' desaturated kage, a crisp waveless shine), and Modern (a gently softened tone, the depth rim, the marched contact shadows and the camera key — the current pipeline in one click). Every value is a starting point; the menu never touches your paints, textures or the key's angle, and the shadow colours are multiply tints, so one style serves any palette. The Cartoon Era menu grows Wartime Noir (the dark 40s theatrical short: a deep hard transparent shadow pushed onto the lit side) and Modern Flat (one barely-darker cool tone over heavily simplified forms — the thin-uniform-line era). Five more Cel & Film render presets bracket the century: the worn silent nitrate with the projectionist's cue discs, the 35 mm anime feature, the 2000s digital transition (no film in the chain at all), the modern 1080p master with its one fine grain sheet, and the modern flat TV cartoon. Three new shelf recipes tie in, generated from the same tables so the shelf and the menus can never drift (112 templates).

The Xrd study (1.82) — the Guilty Gear techniques, from the sources themselves: Motomura's GDC talk and Arc System Works' own line-control deck. Line Control (the material's Ink row): the mesh's vertex colours steer the line exactly as ASW paints them — ALPHA multiplies the width (0.5 the width as set, 1 double, 0 erases the line at that vertex: a glove's rim, a sleeve's opening), BLUE holds interior and marked lines back until the surface turns toward its silhouette (their hull's depth push — the nose line that only draws in profile); silhouettes always keep their line, and Halcyon's screen-space ink never needs their distance compensation. Vertex Colour AO now works under every Compatibility mode — the GDC talk's "offset on the Threshold" for hand-painted models, no game texture required. Face Shadow (SDF) on the Anime Shader: the modern anime face's terminator is DRAWN in a map, not found on the normals — link the game's own face map (or any gradient chain) and it sweeps with the key's angle about the head's frame (Face Forward / Face Up), mirrored across the face's centre line, exactly the convention Guilty Gear and the HoYo titles share; cast and screen shadows still land on it. And the study's foundation was already here: hand-edited custom split normals travel — Blender's Data Transfer from a sphere, the Normal Edit modifier, any sculpted normals reach both devices, and because Halcyon's line is a post-process, edited shading normals never bend the outline (Xrd needed a second normal set for that; a distance-field line gets it by construction).

The cel's light (1.81) — better shadows and better lighting for the 2D shaders, the way the drawings and the 3D-anime pipelines actually do them. A hand-drawn cel is not lit by lamps in a room: the key is decided per shot, its cast shadows are drawn shapes, and the silhouette carries a rim. The Cartoon and Anime Shaders now name their Shading Light: Scene Lamps (as before), Camera Key — one key fixed to the camera by Light Azimuth and Light Elevation about the screen, so the character is lit the same way on screen wherever the camera goes — or World Key, fixed in the world. Under a fixed key the lit tone is the paint as painted, and the scene's lamps only CAST: their shadow maps still fall across the cel. Screen Shadow is the drawn contact shadow — the hair's across the brow, the chin's on the neck — marched from the frame's own depth toward the key over Screen Shadow Length pixels: what is nearer along the way shadows the pixel, crisp and close, on both devices from the same field. Rim Mode ▸ Depth Rim is the anime rim: a band Rim Width pixels wide just inside the silhouette, wherever the surface a few pixels along the screen is farther — a line of light that keeps its width whatever the form, on the Lit Side, the Shadow Side or Both. Smoothing Shape gives Shadow Smoothing a Sphere (as before), an upright Cylinder (the terminator runs straight down a limb) or Facing the Camera — the anime face rule, the whole face one lit plane with only the drawn shadows on it. The Cartoon Shader gains the Anime Shader's Airbrush (colour, width and side) against its own shadow edge. Three templates carry the recipes: Cel Camera Key, Cel Anime Face, Cartoon Rounded Feature. Every existing file renders bitwise as before.

The print's wear (1.80) — the 40s arc's last front and the field's ask ("the grain and hairs need to be much more customizable and interesting"). Display ▸ Cel Film ▸ Print Wear, each thing where it happened to the film: Grain is the negative's silver printed through — a sheet of grains of Grain Size, a Grain Clump share in clumps, each record's own sheet by Grain Chroma (coloured grain, the way three negatives print), density noise strongest where half the grains developed and nothing at the clear gate or at D-max, so a print's whites and blacks are clean. Dust in three populations: Cel Dust sat on the cel under the rostrum camera and stays for every frame of a hold; Negative Dust blocked the printer light and prints clear — one record's colour missing under the three-strip process; the rest is dirt on the print, fresh per frame. Hairs are caught in the projector gate: anchored at the aperture's edge, dancing for their Hair Hold, about Hairs at a time. Scratches run the frame's height at one place for their Scratch Hold, on the emulsion side taking the dye away (neutral on a dye-transfer print, one colour on a two-colour one, blue on a chromogenic one) or on the base side scattering the lamp. Reel Length puts the projectionist's cue marks top right — four frames, eight seconds and one second before every reel's end. Sizes are given at 1080 lines and scale with the frame's height. The chain now runs in the order the light met it: cel dust, optics, process, grade, the print's wear, dirt, weave, hairs, flicker.

The colour process (1.79) — the film look rebuilt around what actually happened to the cel, the study's fourth rank and the field's own complaint ("the coloured ones don't really work well, it doesn't look like the cartoons do"). Display ▸ Cel Film ▸ Colour Process: not a grade but the chain — the camera's black-and-white records through their red, green and blue filters (a successive-exposure or three-strip camera; the filters' cross-talk included, and Filter Sharpness for the taking filters' cut: sharp-cutting filters separate the records further than the eye separates the colours — the three- strip's more-than-life saturation, from the filters, not a saturation dial), halation in the negative's base (each record's bright areas veil their surroundings in their own colour), the timed print's curve to a dye amount (the Hurter–Driffield straight line of Print Gamma in log exposure, pinned so a white cel prints clear and no light prints Dye Density, the H&D toe between; a mid grey prints at 0.18^gamma — 1.5 is the theatre's dense print, 1.3 that print as a telecine shows it), the dye-transfer print's three dyes with their documented unwanted absorptions (a cyan that also eats some green and blue, a magenta that eats red and blue, a yellow that eats green — balanced so a grey scale prints neutral and only colours shift: reds deep, greens darker and toward cyan, blues toward purple; Dye Purity walks toward the process's ideal dyes), the silver key printed from the green record under the dyes, the dye layers' registration error (every edge, the ink line included, fringed in colour — the honest misregistration of a printed cartoon), and the projector (the screen's white is the clear gate of a normally timed print). Two-colour is the same chain with two records and two dyes — Cinecolor and the 1930s two-strip: no true green, skies cyan, foliage olive, skin salmon; its dyes' green absorptions are the process, not an impurity. Exposure is the timer's printer light in stops: down prints the whole frame denser and darker, up thinner and paler. Three new Cel & Film presets — 1941 Fleischer (Superman), 1940s Cinecolor short, early-30s two-strip Technicolor — and the 1940s Technicolor feature preset takes the process instead of the grade. The 1.73 stock grades are untouched and still there for the video era.

Media 2 (1.78) — the study's second media front. Direction on Hatching and Pencil Scribble: Form runs the strokes along the silhouette-parallel tangent (the normal crossed with the view — the isophote direction of the classic pen drawing, which wraps a sphere like latitude and follows a cylinder's length), Slope runs them down the form; a turning direction cannot be one lane field, so the node keeps twelve coherent fields at 15-degree steps and cross-fades the two a pixel sits between, and a stroke never breaks. Indication on every converter — Winkenbach and Salesin's rule that a drawing shows detail only where the artist indicates it: link any mask (an inverted Facing draws near the silhouettes and leaves the middle bare; a vertex colour paints where). Placement: Count on Stipple is Secord's stippling — dots of one size whose number carries the tone, from three nested lattices in a fixed order so a darkening tone only ever adds dots and the crowd is evenly spread at every density. Blend on Pencil Scribble and Charcoal is Sousa and Buchanan's tortillon: graphite taken off the paper's peaks and pushed into its valleys — the stroke keeps half its contrast and a soft halo appears around it; the charcoal's tooth flattens to an even tone. Every twin held to media.py; nodes saved before the sockets read Indication 1 and Blend 0 and grow the sockets at load; four shelf recipes (Form Hatching, Indicated Hatching, Counted Stipple, Smudged Pencil). And the GLSL front-end refuses a call with the wrong number of arguments now, as every driver does — it used to zero-fill them.

The inker's line (1.77) — the Imitation Study's line arc 2, chosen by the field as the front after the backdrop. Three roads to a line that is "dynamic and occasionally rough" instead of traced. Light Weight is Goodwin's isophote distance (NPAR 2007): every silhouette point walks inward along the surface's own normal until the key lamp's light returns (Shadow Level), and the line is as heavy as that walk is long — heavy on a broad shadowed flank, a quarter width on the lit side and on thin features, heavier near than far, all from one measurement; the walk stops at the object's edge and at any depth step. Three more line sources on the Outline panel, each an interior class at the Interior Scale on both roads: Form Lines (the valleys of the facing |n·v| — DeCarlo's image-space suggestive contours, found with Steger's sub-pixel valley detector so the line is one pixel wide and the silhouette's own fall-off never fires), Shadow Lines (the terminator inked, as the cel inker traced the painter's shadow boundary) and Tone Lines (a flow-guided difference of Gaussians on the shaded frame — Kang's FDoG, Winnemöller's XDoG — one pixel wide on the dark side of every tone step, a line only where the step is within one surface). And the stroke road: the contour is read as a graph (every pixel and the runs of its eight neighbours — two runs a path, one an end, three a junction) and everything after is a local operation on it, so a pooled band draws what the frame draws: Smooth (Taubin's shrink-free smoothing of the pixel staircase, corners pinned), Pressure (the net turning of the chain — a staircase's jogs cancel, a curve keeps its rate, a corner its whole angle — bears the pen down through curves and leaves a blob at every corner), Overshoot (true ends, chains arriving at junctions and both edges of every corner run past it along their tangents, tapering, about half of them, each by an amount hashed from the point on the surface, so animation holds), and the seeds are drawn back carrying their origin pixel so every width, colour and depth lookup still reads a surface. Anchor: Surface samples the line's noises (weight, roughness, drift, gaps) at the surface point under the line instead of the screen — Kalnins' coherence without a previous frame. Also: the shadow-side weight and the Light gradient read the smooth normal and a point lamp's true direction now (a point lamp's rotation was being read as its direction). Every dial band- invariant bitwise, deterministic, off by default: the plain and styled lines are the previous release bitwise.

The painted backdrop, the painted background road, the setback (1.76) — the pagoda's first tell was its sky, a flat tint in a frame that was otherwise drawn. World ▸ Painted Backdrop is a background painting on a flat panel in front of the camera (aim it with Panel Direction): the gradient brushed in gouache — the brush's streaks along a stroke angle, optional impasto dabs — painted clouds from a stretched three-octave field, dry-brushed or airbrushed at the edge, lit on top and shadowed beneath by the field's own vertical difference, the board's tooth, and a watercolour granulation applied as pigment density in Bousseau's law (C′ = C − (C − C²)(d − 1)). A pan crosses the painting and a tilt climbs it, the way the animation stand's background did; behind the panel the plain gradient continues, the back of the stage. Four looks on a menu: Gouache Day, Watercolour Dusk, Fleischer Night, Storyboard. Evaluated per direction on the CPU on both device roads like every rich sky — exact by construction; mirrors reflect it by the same road. Paint Mode on every material: Cel (everything as before) or Background, which takes the painted background road (Display ▸ Painted Backgrounds): the surface's lit colour laid down as brush strokes Meier's way (SIGGRAPH 1996) — particles fixed on the surface, one hashed sequence per triangle cut to the screen density the stroke size asks, so a camera that comes closer adds strokes at the end of every sequence and never moves one already there; each drawn far to near at a screen-constant size over an abstracted base, its direction from the colour's contours, the surface's silhouette or a fixed angle, bristle-streaked, drying toward its end, lightened or darkened by its own hash — with the ink suppressed on the painting unless the material says Always. The setback is the Fleischer lens on the miniature: Background materials and the sky soften by eye distance while the cels stay sharp, a masked Gaussian so nothing bleeds across the cel's edge. One CPU pass from the shared G-buffer before the ink on either device road; band-invariant bitwise; a cel pixel is never touched; the default paint mode is the previous release bitwise. And the media nodes gained a third Space, View — the camera's sphere, the eye-to-point direction octahedrally unfolded — Lucas Pope's Obra Dinn answer to the shower door: turn the camera and the marks stay on the scene.

The 2D media (1.75) — the verdict's second sentence: "there should be textures/converters specifically for 2D-looking things — paint strokes, pencil scribbling, charcoals, inking". Seven texture nodes on the Halcyon Textures shelf, five of them converters with a per-pixel Tone input (lightness, 1 = bare paper — a Shader to RGB luminance, a Screen Info Facing, a dot with a light direction): Hatching (pen cross-hatching that fills in layer by layer as the tone darkens — the tonal art map, continuous — each stroke wobbling, varying in pressure, drawn in lifted segments, breaking dry, and swelling to solid ink over the last fifth of the range), Pencil Scribble (hatch lanes bent by a curling domain warp that folds into loops past Curl 1, fanned in shallow layers, the graphite catching the paper's tooth so light pressure speckles and heavy pressure fills), Stipple (dots on a jittered lattice whose density carries the tone, a finer lattice closing the darks, the dots merging into solid at the very end the way a stippler reaches black), Charcoal (the stick depositing on a four-part paper tooth, peaks first, streaked along the stroke, smudged by a thumb, banded by its own pressure), Ink Wash (flat washes by level, pigment pooling inside every edge, settling into the granulation, the edges wandering with Bleed); and two textures: Paint Strokes (brush dabs on a jittered lattice, later over earlier through a two-deep painter's composite, turned off the angle by a hashed slope, bristle-streaked, drying toward their ends — link a lit colour into Color 2 and the strokes carry it, the gouache road) and Paper (tooth, fibres, mottle as a height). Every one has a Space: the Vector input (the marks on the surface) or Screen, the camera's own paper — Scale cells across the frame's height whatever the resolution — and a Boil that redraws the marks every N frames through the salt, so a drawing boils on its own clock like the line does; a Seed keeps two materials' hatching from being the same hatching. Every field is the integer hash the pattern library rides, so every one travels to the GPU exactly — the seven GLSL twins are held against the NumPy originals on random points and whole materials against render(); a linked dial refuses by name, the boil rides the frame uniform (no recompile per frame), Screen space is band-invariant bitwise. Seven 2D Media shelf recipes: five shadeless drawings on a Facing tone (hatched, pencil, charcoal, stippled, wash), a Gouache Background, and Drawing Paper with its own relief.

The drawn line (1.74) — the verdict on the ink pack was "decent, but they look artificial; old cartoon outlines are dynamic and occasionally rough", and this round answers it on the distance-field road. End Taper / End Length: the brush lifts and lands — every stroke end and junction is found on the contour itself (a segment has two, a line that vanishes behind an object ends where it meets that object's contour, a closed silhouette has none) and the line thins toward them. Roughness / Roughness Scale: three octaves of edge irregularity, in patches — a slow field decides where the line gets rough, so it is occasionally rough rather than uniformly hairy. Drift: the hand wanders — the line's centre moves in and out of the true contour, the same on both sides of the line. Gaps: dry-brush skips, short breaks where a fine noise runs high, more readily where the stroke is thin. Line Texture: solid ink, Brush Streaks (lighter streaks running along the stroke — the along coordinate is the source pixel's, the across coordinate the signed distance, so the streaks run parallel and unbroken through the line's centre) or Charcoal (a soft bloom around a dark core, the paper's tooth breaking the body). Every dial is a hash of pixel, phase and seed: band-invariant bitwise, the same frame the same line; every default is the previous release's line bitwise. The Cel & Film presets draw with them.

The era looks (1.73) — the cel arc's last front: the cel photographed and printed. Render Properties ▸ Display ▸ Cel Film. Film Stock is the stock's colour response in linear light — Technicolor's purified primaries and cyan shadows, a faded 70s Eastmancolor print (magenta cast, lifted blacks), the 80s telecine, a VHS dub, or black-and-white panchromatic negative — with a Stock Amount mix. Softness is the rostrum camera's optics (a Gaussian, sigma in pixels); Gate Weave shifts the whole frame by a per-frame registration error; Dust & Hairs puts dirt, clear scratches and the odd hair on the print by density (per film area: about forty specks on a 1080p frame at 1); Grain is the emulsion, seven parts luminance to three parts colour, mean-preserving; Flicker is the projector lamp. Shoot On 2 or 3 is the animator's economy made literal: a held frame is not rendered — the key frame's cel is photographed again (the film stages still run per frame, so grain, dust and weave keep moving) and an animation on twos renders in half the time; render sequences from their first frame, and a frame whose key frame is missing says so and renders fresh. The Paint box works before the ink: Paint Misregistration slides the painted colour by a per-frame error under lines that stay where the drawing put them, Paint Bleed softens the paint under and past the line. The Print box is the newsstand: Halftone lays four ink screens at the classic angles (cyan 15°, magenta 75°, yellow 0°, black 45°), each dot's area its ink's coverage with the classic inversion above 50%, full under-colour removal, reproducing every grey within a percent; Halftone Pitch is the cell in pixels. Every stage is a pure function of the frame number and the seed — the same frame renders the same bits on either device, in any pooled band — and every default is off: the frame is bitwise the previous release's. Six Cel & Film render presets set a period at once: 1930s black-and-white, 1940s Technicolor feature, 1970s Saturday morning (on threes, through the composite chain), 1980s OVA on LaserDisc, 1980s TV anime on VHS, and the comic print. The full Technicolor chain costs about 0.35 s at 1080p; the dot screen about 0.5 s.

The 80s additions to the Anime Shader (1.72) — the cel arc's third front. Hair Shine paints the angel ring: a band of the shine colour across the object at a fraction of its own height (Height), Width wide, its edge waving around the object (Wave, Waves per turn), on the camera-facing surface, fading only on the underside — light-independent, because it was painted on the cel at a position, not lit — with a thinner Second band that far below. Airbrush lays the cel painter's soft gradation against the first shadow edge: on the lit side the tone multiplies toward the airbrush colour just above the edge and fades out toward full light, on the shadow side the shadow tone blends toward it approaching the edge, or both (Airbrush Side), Width in light units. Shadow Smoothing is the Cartoon Shader's inker's road, shared. And the Line Colour menu: Ink Settings (as before), Iro-Trace — this material's ink line in its own shaded colour per pixel, darkened by Line Darken (hair lines in the hair's tone, skin lines in the skin's, the 80s coloured trace line; it runs the distance-field ink road), or the Line Color socket as a constant of the material's own. Every addition is neutral at its default: a node saved before them shades bitwise as it did, and old files grow the sockets at load. GPU twins for all of it, per-pixel amounts and colours included. Two shelf recipes, Cel 80s Hair and Cel 80s Skin, arm them. On the way, a latent fix to the per-material ink road: a silhouette line now belongs to its nearer surface on the mask road too, so a material's coloured or widened line is whole on its sky side (it was half the global line).

The Cartoon Shader (1.71) is the third master node and the OTHER tradition — "a 40s Looney Tunes cartoon is vastly different to an 80s anime". Its colour is paint, not light: flat, the same under every lamp whatever its energy (a lamp at 40 W paints the same cel a lamp at 2 W does). Where the key lamps do not reach, one painted shadow tone lands, by mode: Transparent Cel (paint × Shadow Color by Shadow Amount — the Golden Age shadow cel, a second exposure through a tinted overlay), Painted (a second flat paint replacing the first — UPA and the television decades), or None (flat paint everywhere — limited animation at its cheapest). Shadow Threshold is where the edge falls on the wrapped light term (0.5 the terminator, higher pushes the shadow onto the lit side), Shadow Softness airbrushes it, and Shadow Smoothing bends the shading normal toward a sphere around the object so the terminator sweeps a form as one clean shape the way an inker simplifies it (a sphere is its own smoothed self, bitwise; a cube gets a curved terminator across a flat face). The highlight is a painted dot, not a reflection — Highlight Size is its radius (0.3 ≈ a 17-degree dot, 1.0 a 60-degree cap), Highlight Softness feathers it, and it only lands inside the lit region of the lamp that makes it. Across lamps the paint keeps the strongest lamp's verdict (a region is lit if any lamp reaches it — the paint never brightens past paint), and Lamp Influence is the one road back toward lit shading: 0 is pure paint, 1 lets the lamps' energy and colour modulate the LIT paint — the shadow tone is a colour and stays one. Rim, emission and opacity ride the master's shared tail. An Era menu writes the sockets to a named starting point — Golden Age (1930s-40s), UPA Modern (1950s), Xerox Era (1960s-70s), Saturday Morning (1970s-80s), 90s Feature, 90s TV (Dark Deco) — and the sockets stay yours afterwards. Shades identically on CPU and GPU, per-pixel chains into Shadow Color, Shadow Amount, Shadow Threshold, Shadow Smoothing, Highlight Color, Highlight Size and Lamp Influence included; a chain into a softness socket refuses the driver by name. The master shader's model menu carries Cartoon (Paint) too, running the node at its defaults.

Convert to Halcyon chooses its shader your way (1.62). The Material panel's converter grew a Detection switch: Automatic keeps reading the source shader (Principled roughness becomes Glossiness, Glass becomes Blinn, Toon becomes Toon), Set Shader forces one chosen model — any of the 19, the Anime/Cel bands included — onto everything it converts.

140 resolution presets in nine categories (1.62, 1.84) — the shelf grew from 75: the handhelds and arcade boards (NES at its true 8:7 PPU pixel, Game Boy, GBA, DS, PSP, Neo Geo, CPS-2, Virtual Boy), the 8-bit micros (ZX Spectrum, C64, MSX, Apple II, Atari 8-bit, BBC Micro Mode 0 with its double-tall pixels, NEC PC-9801), DVD and the anamorphic tape formats (HDV 1440×1080 at 4:3 pixels, DVCPRO HD), bake textures to 4K, DCI cinema, 5K/8K, ultrawide 21:9, vertical 9:16 and A3/US-Letter print.

Cartoon outlines. Ink drawn from the renderer's own G-buffer: object silhouettes, material borders, depth breaks and normal creases, each its own toggle, with width, colour, opacity and over-sky control. Marked Edges draws the edges you marked — Freestyle edge marks, Sharp, creases — as interior ink, hidden-line-removed by the z-buffer's own verdict (each pixel measures its exact distance to its own triangle's marked edges; a marked edge behind a wall simply is not there). And every material has a say: Ink mode (follow / always / never — one inked character in a plain scene, or clean glass in an inked one), its own ink colour, its own width. The ink lands at the internal resolution, so supersampling anti-aliases the line on the way down — clean cel edges with no line renderer. Computed from the same buffers on either device, so the picture cannot differ between them. Render Properties ▸ Shading ▸ Cartoon Outlines, and the material panel's Ink row.

113 material templates on the Pre-Made shelf — Add ▸ Pre-Made in the shader editor, sorted into fourteen families (Metal, Mineral, Glass, Water, Liquid, Wood, Cloud, Cel & Anime, Cartoon, 2D Media, Volumes, Terrain, Surfaces, Effects). Picking one drops its nodes beside your existing graph rather than replacing it. The Cel & Anime shelf (1.68) is the Anime Shader one click deep — a skin/cloth/metal cel trio plus ArcSys and HoYo starters with their compat modes armed, and (1.72) the 80s hair and skin with the shine band, the airbrush and iro-trace lines armed; the Cartoon shelf (1.71) is the Cartoon Shader one click deep, one recipe per era — Golden Age, UPA Modern, Xerox Era, Saturday Morning, 90s Feature, 90s TV — generated from the node's own era table so the shelf and the Era menu can never disagree; the Volumes shelf drops a Halcyon Volume wired to the output's Volume socket — Fog Bank, God Ray Chamber, Cel Fog, Ember Glow, and (1.69) Fire on the Combustion model, Murky Air, and a Voxel Cloud on a 12-cube lattice — so any mesh becomes a marched container. The engine's own 28 — Chrome through Wireframe, Water, Lava, Tile Floor, Brick Wall, Hammered Metal, Leopard, Cloth, Dead Channel — plus:

The Bryce 1995 library, decoded — 46 presets. The original preset collection ships as MetaTools CCmF containers, and Halcyon's parser (core/brycemat.py) cracks them completely: the RLE preview thumbnails, the 976-byte material records (diffuse/ambient/specular colours, the per-channel specular coefficients, transparency, reflection, bump, the metallic flag, the refractive index — pinned by diffing the teaching presets against their own 1995 manual text), and the texture records with their exact colour tables, frequencies and octave counts. Polished Gold through Kryptonite carry the stored numbers: the glass ladder refracts at 1.12/1.52/1.68, Water at 1.33, Diamond at 2.55, and Kryptonite is the anisotropic reptilian-scale crackle its own colour table says it is. Preset notes quote the original library descriptions. Built at runtime as recipes rather than saved node trees, so they always match the current nodes, and every one is rendered by the test suite to prove it changes the frame.

34 procedural texture nodes, 27 of the kind these packages shipped — Marble, Wood, Granite, Dents, Crackle, Plasma, Ripples, Caustics, Starfield, Weave, Scratches, Tiles, Spiral, Cells, TV Static, Fur Tufts (the shell-fur field: round strand cross-sections that taper per layer) and the POV-Ray family (Bozo, Agate, Leopard, Onion, Bumps, Wrinkles, Brick), plus:

Fractal Noise — the integer-hash fractal in three profiles, on a 1D, 2D, 3D or 4D lattice with a W socket. The hash travels to the GPU bit-for-bit, which Blender's own sin-fract noise cannot.
Water Noise — 1 to 12 drifting layers folded toward crests by Choppiness, with animation Speed and a Loop that closes the cycle exactly over Loop Frames by moving time onto a circle through the lattice's fourth dimension. A looping deck breathes and shimmers in place rather than drifting; that trade is stated on the node.
Gradient (Shaped) — linear, reflected, spherical, quadratic, square, diamond, conical and spiral falloffs with Centre, Rotation, Scale, clip/repeat/ping-pong and easing.
Matcap Coordinates — sphere-map UVs from the view-space normal, now with an Offset socket and a Centered switch, so a Spherical gradient fed the vector lands centred instead of cornered.
The 2D media (1.75, 1.78) — Hatching, Pencil Scribble, Stipple, Charcoal, Ink Wash (converters on a per-pixel Tone and an Indication), Paint Strokes and Paper, each with a Space (surface, the camera's paper or the camera's sphere), a Seed and a Boil; hatching and scribble with a Direction (angle, form, slope), stipple with a Placement (size, count), pencil and charcoal with a Blend.

Each pattern is written from its published definition rather than from something that looks similar. Agate's 0.77 exponent is the whole character of that pattern. And where the published definition looked nothing like the real thing, the real thing won: Leopard draws true rosettes — curved dark arcs broken around a warmer interior patch, the odd solid spot between, a gentle domain warp bending every ring organic — with ground, ring and Interior colours on separate sockets and the ring mask on Fac, instead of POV-Ray's summed-sines polka dots.

30 more nodes in two families (1.60). Fifteen Utilities — among them a Light Meter that reads how lit the surface actually is at shade time (Fac and per-lamp Color out, optional shadow test), which is the whole trick behind glow-in-the-dark and light-reactive materials; a Timer, Oscillator, Counter, Pulse, Gate, Selector, Color Key, Measure, Step Ramp, Wobble, Frame Blend, Blackbody, Compare and On Frame. Light Meter reads the lamp list at shading time, so the GPU plan refuses it by name and that material shades on the CPU. And fifteen Vector nodes — among them Array, which lays a decal's UVs out along a line, grid, circle, square, polygon or star with per-copy jitter and rotation (made for stamping image decals; following seams, creases or sharp edges needs mesh edge flags the exporter does not carry yet, and is stated on the node rather than faked); plus Mirror Tile, Kaleidoscope, Polar, Twirl, Lens, Ripple Warp, Wave Warp, Tile Random, Snap, Shear, Orbit, Region, Projector and Spin.

The Add menu is families now. Add ▸ Halcyon opens Pre-Made, then Shading, Blender Internal, Utilities, Vector, Retro Screen and Textures as submenus — 92 nodes (64 shader, 27 texture, BI Texture) sorted where a person would look for them, and a census test proves every registered node is reachable from exactly one family.

Colour tools with taste: a Color Ramp (Spaces) node blends up to six stops in RGB, OKLab, OKLCh (hue taking the short way round) or HSV — stop colours are sockets, so they can be driven — and a Blur node that truly re-evaluates whatever is plugged into it at shifted points in the surface plane, procedural or image alike, at three tap qualities. Blur's re-run is CPU work and says so: the GPU plan refuses it by name and that material shades on the CPU.

Coded shader nodes. A real compiler — preprocessor, recursive-descent parser, type inference, and NumPy code generation with SIMT execution masks. Declare a uniform and an input socket appears, named and defaulted from the declaration:

uniform vec3 tint = vec3(1.0, 0.6, 0.2);
uniform float rimPower = 2.5;

in vec3 vNormal;
in vec3 vView;

out vec4 Color;

void main() {
    float rim = pow(1.0 - abs(dot(normalize(vNormal), normalize(vView))), rimPower);
    Color = vec4(tint * rim, 1.0);
}

That gives you a node with Tint and Rim Power sockets and a Color output. Edit the source, press Compile, and the sockets rebuild while keeping every link that still has somewhere to go. Coded shaders compile natively into the GPU's deferred pass too, mangled and inlined, so the same source runs on both devices.

Nine sky modes — node tree, solid, gradient, banded gradient (the same blend cut into the handful of flat steps a 256-colour palette could actually spare for a sky), starfield, Preetham physical sky, HDRI with rotation and tint, and a full Bryce Sky Lab: sky dome, sun corona, haze that warms toward the sun, separate ground fog, a wind-streaked stratus deck, a self-shadowed cumulus deck built from turbulence rather than fBm (which is where the cauliflower edges come from), a rainbow at the correct 42 degrees, stars, comets that travel their own great circles off the scene's clock — and now a nebula wash under the Bryce dome as well as the starfield, because a night preset that sets nebula settings should get a nebula. The ninth, the Painted Backdrop (1.76), is described with the 40s arc above.

303 sky presets, every one with a rendered thumbnail. The original 43 plus 260 new skies in 26 authored families — Golden Hour, Blue Hour, High Noon, Storm Front, Ember, Midnight Clear, Vapor Dream, Winter Overcast, Desert Dusk, Alien Twilight, Monsoon, Candy, Nebula Night, Fog Bank, Thunderhead, Moonrise, Cinema Grade, Arctic Night, Sea Dawn, Toxic, Haze Valley, Comet Watch, Cirrus Day, After the Rain, Noir and Spring Front — each variant carrying its own tooltip. The preset picker is a browsable gallery: the engine's own sky module drew all 303 thumbnails, and a test holds the library to it — real fields only, real notes, a thumbnail per key, and every preset must actually change the sky it is applied to. Save As... writes a .halsky anywhere, Add to Library puts one beside the built-ins. Applying a preset refreshes the rendered view immediately — it tags the world the way a slider does, which for a long time it did not.

48 water presets in the same shape, under the water plane rather than the Sky Lab because that is where Bryce kept them — including a Bryce-1995-shaped ocean set. Skies and waters own disjoint halves of the world, so applying one never disturbs the other.

Nine infinite grounds, and they answer the scene's lighting — solid, checker, fractal, tiles with grout width, grout glow and per-tile shading (thin bright grout past glow 1 is the synthwave neon floor), dunes with a ridge-strength dial, snowfield with sun-glints in their own colour and sparkle amount, lava with pulsing cracks, ember colour and crack-width dials, a Material ground that evaluates any picked material's node graph to the horizon, and the full animated ocean: a directional wave spectrum fanned off a wind direction, deep and shallow colours with the path length between them, and the sun's glitter found in the distribution of wave normals rather than painted on. All intersected analytically in the background pass, exactly as POV-Ray and Bryce provided one — and, unlike theirs, lit by the scene: every lamp's falloff, the hemi wrap, the area-lamp form factor, and cast shadows from geometry, ray-traced or shadow-mapped per lamp, with a Scene Lighting dial whose zero restores the self-lit flat look bit for bit. The self-luminous parts — lava heat, neon grout — keep burning inside shadows.

Weather — rain, snow, embers and ash as a screen-space particle field composited in front of the finished frame, layered for parallax, resolution-true, and a pure function of (seed, layer, index, time): the same frame renders identically across runs, devices and supersample factors, and scrubbing the timeline is stable because nothing integrates.

A terrain generator — Add ▸ Halcyon ▸ Terrain drops a fractal heightfield in seven landforms (mountain, hills, canyon, dunes with a wind direction, crater, volcano, plateau), deterministic per seed and ready-wired to the Altitude & Slope node, which grades a material by height and steepness — with an optional noise socket to roughen the band edges, and a ColorRamp downstream is the classic snow-line in two nodes.

Halo materials — the era's glow sprites, splatted against the frame's own depth: images, noise breakup, colour ramps over radius, rays, star spikes, lightning bolts, shockwave rings, halos along curve objects, and lens flares that sample their lamp's visibility off the z-buffer. A sky-only scene can flare; a halo behind a wall cannot.

Animation, told honestly — sequence renders print per-frame time and a completion estimate that knows the first frame pays for the caches the rest reuse (shadow maps, BVHs, compiled shaders), so the ETA converges on the truth instead of the warm-up cost.

The image-as-palette road — point the quantiser at any image and the whole render is forced through that image's colours; an image-editor operator turns any picture into a one-pixel-per-colour palette table to feed it. Both dither roads clamp before they quantise and before they diffuse, so an unrepresentable hue becomes the nearest palette colour instead of a smear.

90 render presets across seven categories — 3D software (Infini-D, Ray Dream, 3D Studio, MAX R2 and 3ds Max 2012, trueSpace, LightWave, POV-Ray, Bryce, Softimage|3D and the rest), home computers (VGA Mode 13h through PC-98 and X68000), consoles (PlayStation, Saturn, N64, Voodoo, Dreamcast…), broadcast (Video Toaster, PAL, VHS), handhelds, the early web (GIF, JPEG, CD-ROM FMV), and fourteen Cel & Film presets from worn silent nitrate to the modern digital master. Applying one resets everything first, so presets never accumulate.

Render passes — Depth, Normal, Position, UV, Object Index and Material Index, written under Blender's own names and channel layouts so a Halcyon Z pass drops into a comp built for Cycles without rewiring.

291 settings, all exposed, all proven, all explained. Two tests stand behind that sentence: one holds every setting to a proof that it changes what it claims to change (a matrix row, an A/B render, a behavioural check, or a declared reason — nothing silently exempt), and one fails the build the moment any property ships without a detailed tooltip.

Legacy import: any 2.79-or-earlier .blend, materials included — the headline feature, described in full above: File ▸ Import ▸ Legacy Scene, the automatic fix-up on plain File ▸ Append, Blender Internal materials and all eighteen texture slots rebuilt one to one, lamps with their real energies, and the old world as sky, ambient and fog.

Design notes

The pipeline

supersample → rasterise z-buffer → reconstruct fragment attributes
→ evaluate node graph per material → collapse closure to a reflectance model
→ light → ray-traced reflection/refraction → A-buffer transparency → fog
→ cartoon outline ink                  [from the G-buffer, both devices]
→ filtered downsample
→ glow / star / flare (linear light)
→ display transform
→ colour depth + dither + palette      [the framebuffer]
→ composite NTSC encode/decode         [the cable]
→ interlace                            [the signal]
→ CRT mask, scanlines, curvature       [the glass]
→ JPEG artefacts                       [the file]
→ pixel aspect and nearest upscale

Glow happens before quantisation and scanlines after it. That is not a stylistic preference — a 1996 machine glowed in its framebuffer and scanned on its tube, and doing it in the other order looks wrong in a way that is hard to name but easy to see.

Determinism

The same frame renders the same pixels — across runs, across thread counts, and across devices. That is a doctrine with machinery behind it, not a hope:

Every stochastic effect (soft shadows, AO, dither jitter) draws from an integer hash that is a pure function of (pixel, sample, stream, seed), and angles come from a shared 256-entry table rather than anyone's sin.
Ties are named rules, not races. The rasteriser resolves coverage ties to the lowest triangle id; the ray tracer resolves equal-distance hits the same way — the answer is a function of the candidate set, never of traversal order or scheduling.
Where a driver's last-bit arithmetic genuinely cannot decide reproducibly — a reflection ray grazing two coincident surfaces — the GPU routes the tie to the CPU and returns the reference's own answer by construction. Route, never guess.
Every internal data texture on the GPU is read by texelFetch with integer coordinates, never through a sampler whose filter state the Python API cannot control. That one is written in scar tissue: a filtered read of the triangle-id buffer once drew a faint wireframe over every edge of a scene, visible only at resolutions the test suites never rendered.

Closures to reflectance models

Blender's node graphs produce Cycles-style closures: additive, weighted lobes. A 1990s renderer has one shader with a diffuse term and a specular term. The translation sums the weighted lobes into those two slots and infers the model from what the tree contains. It's in core/render.py:closure_to_surface and documented there. It is an honest lossy mapping, not a pretence that the two systems are the same.

Roughness maps to a Phong/Blinn exponent by the classic 2/r⁴ − 2 relation, clamped.

Transparency

A true A-buffer (Carpenter 1984). Every transparent fragment is shaded and kept; fragments are then sorted per pixel and composited by layer rank. It is correct through any depth of overlapping surfaces, unlike the per-object sorting most period renderers used — which is also available, as Painter's Algorithm, because its failures are part of the look. Screen Door transparency punches dither-pattern holes instead: no sorting, no blending, pure period.

Alpha Clip (punch-through) is the material panel's other alpha mode, and the era's cheap one: the alpha chain is tested against a threshold and the surface is either fully there or fully absent. Its pixels resolve in the z-buffer before shading and shade once — no layers, no sorting, no per-layer GPU passes — which is exactly why fur, foliage, fences and cut-out sprites cost almost nothing on 1990s hardware. Fur Shells materials use it automatically; the suite holds the clip road pixel-identical to the A-buffer's answer on hard-alpha scenes.

Shadows

Shadow maps are compared in linear light-space distance, not NDC z, so the bias is a world-space number that means something. Normal-offset biasing — stepping off the surface by a texel or so, scaled by how obliquely the light hits — removes acne without the detached shadows a large depth bias causes. Shadow maps and shadow rays agree to within 0.0015 mean difference on the test scene, which is the real evidence that both are right. Point lights get proper six-face cube maps, and the same depth images travel to the GPU as atlases.

Rays

The BVH builds by binned surface-area heuristic — a median split over a scene with a huge ground plane produces sibling boxes that overlap almost entirely, and the profiler measured shadow rays paying for both subtrees all the way down. The SAH tree made the field scene's shadow rays 12× faster and its reflection rays 6×, on both devices at once, because the GPU kernels traverse the same packed tree. Traversal on the CPU runs level-synchronous waves of (node, ray) pairs — a few dozen large array operations per query instead of thousands of small ones.

The bpy boundary

Everything under core/, shaders/ and the numerical half of gpu/ imports NumPy and nothing else. No bpy. The exporter flattens node trees into plain dicts, bakes colour ramps and curve mappings into 256-entry LUTs, and hands over dataclasses. That boundary is why the whole renderer can be tested headlessly, and it is the reason the test suite below exists at all.

properties.py is generated from the RenderSettings dataclass, so the UI cannot drift from the renderer. A test asserts every field has a matching property; another asserts every property has a reader inside the engine, which is how seven corpse settings were found and removed.

Running the tests without Blender

python3 -m halcyon.tests.run_all              # shader + renderer tests
python3 -m halcyon.tests.run_all --images out # ...and write demo PNGs

The suite covers the shader compiler (divergent control flow, loops with per-lane trip counts, out-parameters, early return, structs, matrices, swizzle assignment, discard, the preprocessor, both dialects, error reporting) and the renderer (geometry landing where independently projected, shadows by both methods agreeing, every shading model distinct, all debug passes, affine texture warp, vertex snapping, A-buffer transparency, ray-traced reflection to any depth, node-graph evaluation including group recursion and unknown-node fallback, palette colour counts, the full post chain, the generated period objects, all 86 templates rendering, all 303 skies applying and differing, all 75 presets, every setting's proof, and every tooltip's existence).

The GPU pipeline is tested headlessly too: the same GLSL the driver compiles is executed by the compiler's own NumPy backend against the same packed textures — raster kernel, deferred shading, ray kernels, post stages — so a change that would move a GPU pixel fails the suite on a machine with no GPU at all. The final word still belongs to hardware: Run Self Test renders the 116-row feature matrix on your actual driver and reports any row where the two devices disagree.

Set HALCYON_DEBUG=1 to make node evaluation raise instead of falling back silently — useful when a material isn't doing what you expect.

The GLSL / HLSL subset

Verified working:


Preprocessor	`#define` (object and function-like), `#ifdef`, `#ifndef`, `#if`, `#elif`, `#else`, `#endif`, `#undef`
Types	`float` `int` `uint` `bool`, `vec2/3/4`, `ivec`, `bvec`, `mat2/3/4`, `sampler2D`, user `struct`
HLSL aliases	`float2/3/4`, `float4x4`, `cbuffer`, semantics (`SV_TARGET`, `TEXCOORD0`, …)
Control flow	`if`/`else`, `for`, `while`, `do`, `break`, `continue`, `return`, `discard`, `switch`
Functions	user functions, `in`/`out`/`inout` parameters, overloading by arity
Arrays	declaration, indexing, assignment, per-lane divergent dynamic indices
Swizzles	read and write, `xyzw` / `rgba` / `stpq`
Derivatives	`dFdx`, `dFdy`, `fwidth` — real screen-space differences, not stubs
Textures	`texture`, `texelFetch`, `textureSize`, `textureLod`, `textureGrad`
Extras	`noise3`, `fbm`, `quantize`, `posterize`, `dither4x4`, `hsv2rgb`

Divergent control flow is handled with execution masks, so different pixels genuinely take different branches and run loops for different numbers of iterations.

Not supported:

Recursion. Rejected at compile time with the call cycle named. Under SIMT masking every lane walks both sides of a branch, so a recursive call never reaches its base case.
Array constructor syntax — float[3](1.0, 2.0, 3.0). Declare and assign instead.
Geometry, tessellation and compute user stages. User shaders are fragment-language only (the engine's own kernels use compute internally).
sampler3D, samplerCube, integer textures.
Uniform block layout rules — cbuffer members are flattened to plain uniforms.

GPU support

The port is complete: rasterisation, shading and post all run on the GPU, through Blender's own gpu module — the layer EEVEE is built on, and the only route an add-on has. Set Device: GPU in Render Properties and the three stage toggles come on together.

Rasterisation runs as a compute kernel producing the same G-buffer the CPU produces — triangle ids, perspective-correct barycentrics, depth at the chosen precision, the affine-warp interpolants, snap and 16-bit modes included. Coverage at shared edges is governed by the same watertight window and canonical clip rules on all four engines (CPU loop, CPU batch, GLSL kernel, NumPy replay), because a half-ulp disagreement near the near plane once opened pixel-wide cracks.
Deferred shading packs the G-buffer into textures and shades one full-screen pass per material, every frame constant baked into the shader source. Lights, shadow atlases (cube faces included, every Vogel PCF tap reproduced), image textures with the CPU's own filter arithmetic, vertex colours, per-pixel surface parameters, the master shader's whole colour chain, coded GLSL nodes inlined natively, and the ray sweeps — reflections and refractions to any depth, traced by compute kernels against the same SAH tree, with each level's secondary passes scissored to the pixels its rays actually hit.
Post runs the parallel stages as GLSL, measured stage by stage on real hardware before each was allowed to default on. Error-diffusion dither is inherently serial and stays on the CPU, honestly.

The whole matrix — 116 feature rows — is compared against the CPU picture by Run Self Test on your own driver. A row that cannot yet run on the GPU is routed: the frame says why on the console and shades that part on the CPU, so the picture is always right and the reason is always named. The same honesty applies at runtime — if the GPU path cannot deliver a frame (a driver hiccup, a timeout under a heavy foreign add-on), the frame renders on the CPU with the reason printed, never half-drawn.

Frame-to-frame, unchanged uploads — shadow atlases, mesh attributes, texture pixels, the BVH — are cached behind content fingerprints, so an animation re-uploads what moved and nothing else. The console prints a per-stage split (raster clip/pack/dispatch/read, shade plan/upload/draw/reflect/composite, and inside reflect: trace, secondary draws, sky-along-misses, levels run and skipped), so when a frame is slow, the stage that owns the time names itself.

Known limitations

These are real, and I would rather write them down than have you find them.

The Blender layer is only partly validated here. Two levels of stand-in exist: one imports and registers every module against a bpy stub, and one runs a whole frame through HalcyonRenderEngine.render() — property group, exporter, renderer, post chain, delivery and passes — against a fake depsgraph. Neither can catch a segfault, a driver quirk or an RNA lifetime bug. If something misbehaves, the traceback in Window ▸ Toggle System Console is the fastest way to tell me what happened.

Blender's procedural textures differ slightly from Cycles. Noise, Voronoi, Musgrave and Magic are independently implemented from their published definitions — the right kind of pattern with the right statistics, not bit-identical to Blender's, so a material tuned against Cycles may need a nudge. They also cannot travel to the GPU (their sin-fract hash decorrelates on a driver's float32), so they route those materials to the CPU by name. Halcyon's own pattern nodes ride an integer hash that is bit-exact on both devices — the Fractal Noise node exists precisely to be the portable replacement.

The Sky Texture is Preetham, not Nishita. In period, driven by the same sun inputs, and close enough in shape for output about to be quantised to 256 colours. altitude, air_density, dust_density and ozone_density are exported but unused.

Volumes are real now — and stylized (1.66). A mesh whose material output links a Volume chain (Halcyon Volume, Principled Volume, Volume Scatter/Absorption) becomes a container: every camera ray marches its bounding box — the era's volume gizmos were boxes and spheres — accumulating per-channel Beer-Lambert absorption and single scatter from the scene's own lamps, falloffs, gobos, light linking and per-lamp shadows included; a shadowed lamp carves god-rays through the fog. Whatever chain feeds Density is evaluated at every march sample with Generated coordinates spanning the box, so a Bozo or Cells chain shapes clouds exactly as POV-Ray's media and 3D Studio's Volume Fog did. The Halcyon Volume node adds the cel half: Edge Threshold/Softness cut hard anime cloud edges from soft density, Bands posterizes the scattered light into cel steps, Shadow Tint makes a shadowed region take a COLOUR rather than darkness. Fixed-count midpoint marching, deterministic per pixel; low step counts band, and the banding is the era's own slicing artefact. A baked fluid-sim DOMAIN feeds its smoke voxels straight into the march (trilinear, defensively read — an unbaked cache says so and falls back to the node chain), containers split per object, and traced reflections pass through containers rather than reflecting a black box. Fog Bands quantizes the depth fog itself into hard cel steps — distance as flat painted planes. The screen-space kinds remain alongside: light shafts smeared from bright pixels, the visible beam cones, Height Fog.

Volume models, container shapes, voxels (1.69). The Halcyon Volume node carries a Model menu like the master shader's: Henyey- Greenstein (the default), Uniform, a dual-lobe cloud phase, POV-Ray's Rayleigh / Mie haze / Mie murky media types, and two unlit atmospherics from 3D Studio — Volume Fog (the fog colour composited by density, exactly Color × (1 − T), no lamps) and Combustion (the Fire Effect: Color is the sparse outer flame, Emission Color the dense inner one, brightness follows density, Absorption sets how much the flames hide). Every lit law is normalised to unit integral, so Color stays the albedo whichever you pick. Shape decides what the ray marches: Mesh (the default now — the container's own faces, depth-peeled by the engine's rasteriser, so a sphere is a sphere and a torus keeps its hole; a mesh that IS its bounding box takes the box road bitwise), or the Box / Sphere / Cylinder gizmos of the era's atmospherics. Voxels reads the density and colour chains — and a smoke grid — at the centres of an N³ lattice over the bound: the blocky voxel volume of the era's grid volumetrics, 0 for continuous. Mesh containers use their face winding to tell inside from outside (recalculate normals outward if a shape inverts) and keep up to four solid spans per ray.

The ink style pack (1.70). The Cartoon Outlines panel's Line Style box draws the line from a distance field the moment any dial leaves its default: Clean (the trace machine's crisp even line — the 80s cel), Brush (a soft bleeding edge) or Pencil (offset strokes with grain); Depth Taper (thick near, thin far), Interior Scale (thin creases under a thick silhouette), Weight Noise (the hand's pressure along the line), Shadow Side (thicker where the surface turns from the key lamp), Boil on a clock (on twos, on threes, or one static wobble), Grain, a line colour From Fill (the self-coloured line of hand-inked features and iro-trace anime) or a Gradient by depth, height or light, and True To Height so a 4K frame keeps its line. Defaults are the plain mask line, bitwise; pooled bands draw the whole frame's line (a seam under thick outlines, there since the outline pass shipped, is gone).

Textures drive volume density (1.69.1). Feed Density any chain and it is evaluated at every march sample: Halcyon's own patterns (Bozo, Cells, Fractal Noise) and Blender's procedurals (Noise, Voronoi, Wave, Magic, Musgrave types) shape the fog in 3D. A volume sample carries the pixel, the eye, the clock and its object, so Texture Coordinate ▸ Window projects an image from the camera through the fog (a drawn cloud, lit and shadowed as a volume), Object follows the container's matrix, and scrolling or clocked chains animate. A 2D image with no Vector extrudes along the box's Z (Flat reads the Generated XY); set its projection to Box and the three axis projections average into one solid texture from a single tile. Blender 5.x renamed the texture nodes' "Fac" outputs to "Factor" behind an unchanged identifier — Halcyon reads the identifier now, so those outputs no longer resolve to zero (the "textures make the volume vanish" report), and a chain that fails for any reason is printed by name instead of shading a silent zero.

Area lamps light by their shape (1.69). A Disk or Ellipse area lamp runs BI's Stokes contour over an equal-area 16-gon instead of its bounding rectangle, normalised by the emitting area (π/4 of the rectangle) so a disc and a square of the same size throw the same energy and differ only in shape — as the soft shadows and beam cones already did. The rectangle shapes are the compiled-C road bitwise; the GPU twin bakes the polygon's corners.

Every lamp projects a gobo. Load an image into a lamp's Projected Texture box: a Spot throws it through its cone like a slide projector, a Sun/Hemi tiles it along its rays as a cloud shadow, a Point wraps it around itself lat-long like a pierced lantern, an Area carries it on its face like a printed gel. The lamp's Angle/Radius softens the projection exactly as a bigger source would (baked into the image once, so both devices read identical texels); extension (Era Default / Repeat / Extend / Clip — Clip is the projector's gate) and interpolation (Bilinear / Closest / Cubic) are per-lamp choices, mirrored texel-for-texel in GLSL.

Depth of field is layered, not sampled. Depth slabs, each blurred by its circle of confusion — a handful of blurs instead of hundreds of rays, as compositors of the era did.

Displacement drives a bump, not geometry. The height becomes a normal perturbation from its screen-space gradient. Nothing is tessellated, which is also what 1990s scanline renderers did.

Ambient occlusion and radiosity are not period-universal and are off by default. They're there because they're occasionally useful and, in radiosity's case, because the era's boxes did ship it.

Hair and particles render. Particle-system hair and Curves-object hair export as camera-facing tapered ribbons — the primitive Blender Internal rendered strands as — children and emitter root UVs included, with the Hair Info node live on both devices (Intercept, Random, Length, Thickness off a documented colour-layer convention any custom mesh can adopt via the material panel's Hair Geometry switch). Add ▸ Halcyon ▸ Fur Shells grows the era's other hair on any mesh: shell texturing with an auto-wired tuft-threshold material, root-to-tip ColorRamp included — and its dials (shells, length, packing, comb, density, colours) stay live in Object Properties ▸ Halcyon Fur, re-growing the pelt as you drag, with a Rebuild From Source button for when the source mesh itself changed. The pelt wears its source: vertex groups, shape keys (as per-shell deltas), deforming modifiers (Armature above all — rigged fur follows the rig), every UV layer copied loop-exactly, the source's own colour layers, and parenting. Topology-changing modifiers are skipped by name. The fur material rides Alpha Clip, so a pelt renders at punch-through speed instead of drowning the frame in blend layers — and it casts no shadow, because the shadow roads see full quads, never the alpha holes: a pelt that cast would blanket its own lower layers and the body in black (the era's shell fur was never in a shadow map either). Both flags travel with the material and can be flipped in the material panel; the export health check names a casting tuft material with its cure. Emitter particles render as halos when their material is a halo, and as instances when they instance objects or collections. Baking to texture is not implemented. Motion blur is — as averaged time-offset frames across a shutter, which is exactly how the era faked it, at the cost of Steps extra renders.

Mesh, curve, surface, text and metaball objects render; Blender converts each to triangles and Halcyon takes it from there. Hair curves render as strand ribbons, and point clouds as halos when their material is one. Grease pencil and volumes do not, and are named in the info bar rather than quietly left out. An object that will not convert is skipped with its name reported — one bad object costs you that object, not the frame.

Performance

Profile first. Developer Options ▸ Debug ▸ Timing Breakdown prints a per-stage table for every frame, and the GPU path prints its own splits down to the reflection sweep's internals. Three rounds of optimising this engine were once aimed at whichever stage happened to have been profiled, and twice that was not the stage the frame was spending its time in. The engine now optimises the way it renders: measured, on the scene that hurt, with losing experiments written down so nobody re-fights them.

Recent measured wins on real field scenes, every one pixel-identical by test: a 25-material, 171-object character file that first rendered in 8:48 now renders warm in 0.7 s — the arc that got there: SAH BVH (shadow rays 12×, reflection rays 6×, both devices), light and material values moved into textures so lamp and slider edits re-upload a texel instead of recompiling shaders (and same-structure materials now share one compiled shader), a G-buffer cache so an unchanged camera never re-rasterises, a per-object mesh-export cache driven by Blender's own update reports so an unchanged scene exports in a millisecond, the BVH persisted to disk across sessions under a content digest, the frame's draw calls batched into one main-thread crossing inside one render pass, and shadow rays skipped exactly where a lamp contributes nothing. Losing experiments are written down next to the wins so nobody re-fights them.

The knobs that matter, in order:

aa_samples is quadratic — under Supersample. Supersample 24 renders a 5× frame each way — 25× the pixels. Drop to 1 while you light the scene, or switch Anti-Aliasing to Adaptive (Edge Pass): it renders the frame once, then re-samples only the edge pixels (Bryce's anti-aliasing sweep, POV-Ray's +A), which buys Supersample-grade silhouettes for a few percent of the cost.
Pixel Scale is free performance. Renders at 1/N of the output size and nearest-upscales — 16× cheaper at 4×, and more authentic than shrinking a large render.
Resolution. Also quadratic.
Ray tracing. Reflective materials cost rays; depth multiplies them. The reflect console split will tell you which part owns the time.
shadow_map_size. Each map is a full rasterisation pass; a point light needs six. 512 is usually plenty at these resolutions.
preview_scale controls viewport resolution; the viewport also caches the exported scene and only rebuilds what changed.

Threading, and why processes beat threads

Shading runs across a thread pool and is bit-identical at any thread count — a test asserts it — but NumPy releases the interpreter lock only for large array work, so threads mostly contend. Use Worker Processes splits the frame across separate interpreters instead (possible only because core/ is bpy-free), bit-identical to in-process rendering. For sequences, Lock Palette builds the adaptive palette once, and turning serpentine off lets the error diffusion run a diagonal at a time — bit-identical and two to three times faster.

Layout

halcyon/
  core/          bpy-free renderer
    mathx.py       vector maths on (N,3) arrays
    scene.py       dataclasses the renderer consumes
    settings.py    RenderSettings — the 291 knobs
    raster.py      clipping, z-buffer, watertight edge rules, A-buffer
    bvh.py         binned-SAH BVH, wave traversal, order-free ties
    texture.py     sampling, mips, N64 three-point filter
    shading.py     the 32 reflectance models (Max's eight included)
    lights.py      attenuation, shadow maps, PCF, ray shadows, gobos
    nodeeval.py    243 node types, the bump desugar, the space ramps
    patterns.py    the integer-hash pattern library, 1D–4D noise
    maxmaps.py     3ds Max's map algorithms on Halcyon's own tables
    bitex.py       the ported Blender Internal texture engine (+ tables)
    blend279.py    the 2.79 DNA reader and the BI material mapping
    brycemat.py    the Bryce 1995 .mat decoder — container, previews,
                   material records, texture colour tables
    sky.py         the sky modes, the Bryce dome, the painted backdrop,
                   the lit grounds, the weather overlay
    volume.py      real volumes: containers, eight scattering models
    sss.py         subsurface scattering, the BI way
    celfield.py    the cel's light: keys, screen shadows, the depth rim
    ink.py         the ink style pack: the distance-field line road
    lines.py       the inker's line: isophote weight, form / shadow /
                   tone lines, the stroke road
    media.py       the 2D media converters and paint strokes
    gouache.py     the painted background road, Meier's particles
    film.py        the colour process and the era looks
    wear.py        the print's wear: grain, dust, hairs, scratches
    render.py      the orchestrator, outlines, closure translation
    post.py        glow, palettes, dither, NTSC, CRT, JPEG
    palette.py     median cut, octree, k-means, VGA/Mac/EGA/HAM
    dither.py      Bayer, Floyd-Steinberg, Stucki, Atkinson, …
    geometry.py    the Add-menu objects, the seven terrains
    cones.py parallel.py worker.py stats.py convert.py
  gpu/           the GPU port
    craster.py     the compute rasteriser and its NumPy twin
    shade.py       frame planning, deferred passes, the ray sweeps
    material.py    GLSL assembly per material
    emit.py        178 node emitters
    procedural.py  the pattern, media and Max map libraries as GLSL,
                   twin by twin
    glsl_shading.py  the reflectance models in GLSL
    rtrace.py      BVH kernels, the tie referral
    gbuffer.py     G-buffer packing and exact reconstruction
    device.py marshal.py stages.py chain.py capability.py
  shaders/       bpy-free GLSL/HLSL compiler and its NumPy interpreter
    lexer.py parser.py gtypes.py builtins.py codegen.py compiler.py
    interp.py
  nodes/         Blender node classes: the master, Anime and Cartoon
                 shaders and the BI Material node (shader_nodes.py), the
                 pattern and media shelf (pattern_nodes.py), the 3DS Max
                 shelf (max_nodes.py), the BI Texture node
  presets/       90 render presets, 303 skies (+ thumbs/), 48 waters
  tests/         headless suite, bpy stub, fake Blender, feature matrix,
                 Blender 5.2's icon enum
  docs/          the preview sheets
  legacy_import.py   the 2.79 importer
  append_watch.py    the automatic lamp fix on plain File ▸ Append
  compat.py properties.py export.py engine.py preview.py ui.py
  objects.py convert.py templates.py selftest.py

Licence

GPL-3.0-or-later, matching Blender.

Credits

Built by Claude with help from Mr. Emotiman.

This Addon is and always will be free. If you paid for this, you were scammed. Please demand your money back and report the seller.

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Halcyon

Install

Running the tests

Reporting a problem

Blender 2.79 appending — the headline feature

What it does

Design notes

The pipeline

Determinism

Closures to reflectance models

Transparency

Shadows

Rays

The bpy boundary

Running the tests without Blender

The GLSL / HLSL subset

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Threading, and why processes beat threads

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Name		Name	Last commit message	Last commit date
.github		.github
core		core
docs		docs
gpu		gpu
nodes		nodes
presets		presets
shaders		shaders
tests		tests
CHANGELOG.md		CHANGELOG.md
EXTENSION_LISTING.md		EXTENSION_LISTING.md
LICENSE		LICENSE
README.md		README.md
ROADMAP.md		ROADMAP.md
__init__.py		__init__.py
append_watch.py		append_watch.py
blender_manifest.toml		blender_manifest.toml
compat.py		compat.py
convert.py		convert.py
engine.py		engine.py
export.py		export.py
halcyon_contact_sheet.png		halcyon_contact_sheet.png
legacy_import.py		legacy_import.py
objects.py		objects.py
preview.py		preview.py
properties.py		properties.py
selftest.py		selftest.py
templates.py		templates.py
ui.py		ui.py
version.py		version.py

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Halcyon

Install

Running the tests

Reporting a problem

Blender 2.79 appending — the headline feature

What it does

Design notes

The pipeline

Determinism

Closures to reflectance models

Transparency

Shadows

Rays

The bpy boundary

Running the tests without Blender

The GLSL / HLSL subset

GPU support

Known limitations

Performance

Threading, and why processes beat threads

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