Part mesh / link. Mecabricks imports every element type once as a mesh (e.g. 3001.002, a
2×4 brick); each brick in the scene is an object that links this mesh. A scene may link one mesh
hundreds of times.
Subdivision. Blender's subdivision surface (Catmull-Clark, OpenSubdiv): every face is split and the surface smoothed. Each level multiplies the faces by three to four (a triangle becomes three faces, a quad four).
Crease. A weight on an edge (0–1) that keeps the subdivision from rounding it. Creases are what makes a smoothed brick keep its sharp edges. Renderbricker sets them by rules (RULES.md).
Copy (<mesh> L1, <mesh> L2). The subdivided result for one level, baked into a mesh of its
own. All links of a part use the same copy; the imported mesh stays in the file, unchanged.
Cache file (<scene>_rbcache.blend). A second file next to the scene that holds the copies.
The scene links them as library overrides, so its own file stays small.
Custom normals. The shading directions Mecabricks stores in the import. Variant A carries them into the subdivided copy, so the parts shade as Mecabricks made them.
Headless. Blender without a window, started from a terminal – used by Convert headless and by the background Blenders of Use several Blender processes.
Renderbricks Sky / Renderbricks Sun. The world of the render camera: Blender's physical sky (Sky Texture) with a sun at a height and direction set by the sun sliders. Cycles is lit by the sky and its sun disc; EEVEE takes that sun only very weakly, so with EEVEE a sun lamp Renderbricks Sun follows the sky, with the strength and colour the sun has in Cycles.
Import scale 0.001. Mecabricks parts at their real size in Blender's metric units (a 2×4 brick 3.2 cm long). The reworked Mecabricks importers use it by default; scale 1 makes one millimetre one unit.