Entry 29

Material crop values are a UV animation's reference, not an offset

2026-09-23renderformat

Filesdocs/formats/ccs.mdcrates/piney-data/src/scene.rs

26 found the Material chunk's cropU/cropV nonzero in 218 of 11,071 materials, all on animated UVs and eyes, and left their unit untraced, with the viewer ignoring them. The render page's VU1 formula u = (S + row.x) / 256 suggested they might be a texture offset the viewer was missing. They are not.

• ccMaterialChunk (DWARF, 0x18 bytes) keeps transparency at +0x10 and cropU/cropV at +0x14/+0x16, as 26 read them.
• The runtime ccMaterial has its own pair at +0x14/+0x16. ccMaterial::Init (INF SLUS_202.67:0x001399f0) copies the transparency but stores zero in that pair: it never reads the chunk's crops.
• The chunk's crops are read by ccModel::SetUV(u, v, chunk, flags) (0x0013abe0). For every material of the model that uses the chunk, it sets the runtime offset to u - cropU and v - cropV, with flag bits 1 and 2 skipping u or v. Its only caller is ccAnm::SetUV (0x00152de0), so this happens only while a UV animation runs.

So the crop is the value a UV animation's keys are measured from. A model at rest draws with no offset, and the viewer's static frames were already right to ignore it. The unit of the animated offset belongs with animation playback, which is being worked out separately.