Support user-made textures.
Initial release could support the replacement of 64x64 tiles by texture id in a subfolder and follow up release could support higher resolutions.
Important to keep in mind that texture ids are per-track slot numbers, not globally unique: a flat tex{tex_idx}_{tile}.png naming scheme would apply to whichever track happens to be loaded when that slot is populated, not to one specific track - we need to key the overrides by track filename too, not just (tex_idx, tile).
Car-related banks (1–16, 18) are car-persistent rather than track-specific, but the track/building banks - which is what tile references like "idx=23" or "idx=123" address - are explicitly track-relative and reloaded fresh on every track change.
Each track's data file specifies its own atlas filename via a T: line (and optionally BLD: for buildings, defaulting to building.drh). Loading a track overwrites the fixed bank slots - tex_idx=0 (TEXTURE_BANK_TRACK) and tex_idx=17 (TEXTURE_BANK_BUILDING) - with that track's own pixel data (loadtrak.c -> graphics.c -> scene_render_load_texture). So (tex_idx=0, tile=23) on one track and the same (tex_idx=0, tile=23) on a different track are almost always completely different textures - same slot number, different loaded content per track.
building.drh is the default building/sign texture atlas file — the fallback used when a track's data doesn't specify its own.
Concretely (graphics.c:41-43, loadtrak.c:1378-1419):
- texture.drh is the default track atlas filename (tex_idx=0, TEXTURE_BANK_TRACK)
- building.drh is the default building atlas filename (tex_idx=17, TEXTURE_BANK_BUILDING)
- gentex.drh is a car-generation texture default
Each track's data can supply a T: line to override the track atlas, and optionally a BLD: line to override the building atlas - but read_bldmap (loadtrak.c:1419) falls back to "building.drh" if no BLD: entry is present in the track data.
The .drh files themselves are loaded via getcompactedfilelength/loadcompactedfile (graphics.c:703-733) — a compressed format that decompresses into raw indexed-color 4096-byte tile blocks (64x64 or 32x32 depending on gfx_size), then gets sorted/mapped into the atlas layout via sort_texture/setmapsel.
Support user-made textures.
Initial release could support the replacement of 64x64 tiles by texture id in a subfolder and follow up release could support higher resolutions.
Important to keep in mind that texture ids are per-track slot numbers, not globally unique: a flat
tex{tex_idx}_{tile}.pngnaming scheme would apply to whichever track happens to be loaded when that slot is populated, not to one specific track - we need to key the overrides by track filename too, not just (tex_idx, tile).Car-related banks (1–16, 18) are car-persistent rather than track-specific, but the track/building banks - which is what tile references like "idx=23" or "idx=123" address - are explicitly track-relative and reloaded fresh on every track change.
Each track's data file specifies its own atlas filename via a T: line (and optionally BLD: for buildings, defaulting to building.drh). Loading a track overwrites the fixed bank slots - tex_idx=0 (TEXTURE_BANK_TRACK) and tex_idx=17 (TEXTURE_BANK_BUILDING) - with that track's own pixel data (loadtrak.c -> graphics.c -> scene_render_load_texture). So (tex_idx=0, tile=23) on one track and the same (tex_idx=0, tile=23) on a different track are almost always completely different textures - same slot number, different loaded content per track.
building.drh is the default building/sign texture atlas file — the fallback used when a track's data doesn't specify its own.
Concretely (graphics.c:41-43, loadtrak.c:1378-1419):
Each track's data can supply a T: line to override the track atlas, and optionally a BLD: line to override the building atlas - but read_bldmap (loadtrak.c:1419) falls back to "building.drh" if no BLD: entry is present in the track data.
The .drh files themselves are loaded via getcompactedfilelength/loadcompactedfile (graphics.c:703-733) — a compressed format that decompresses into raw indexed-color 4096-byte tile blocks (64x64 or 32x32 depending on gfx_size), then gets sorted/mapped into the atlas layout via sort_texture/setmapsel.