Entry 53

Models have their own blend: alphaBlendTbl by the header's blend type, and the title's glows are additive

2026-09-23rendertest

Filescrates/piney-desktop/src/anm.rscrates/piney-desktop/src/assets.rscrates/piney-demo/src/draw.rscrates/piney-stream/src/draw.rscrates/piney-gs/src/lib.rs

The user found the title's selection still wrong after 47 and 51:

• behind the selected icon, a hard-edged dark square;
• behind its text, a dark box.

The GPU and the CPU GS model drew the same thing, so the fault was in the draw list, not the renderer.

Finding it

In ccSetMaterialPacket (0x0013e6c0), ALPHA_1 is ccDrawModelParam.alpha (+0x138). ccModel::Draw copies it from the model itself, ccModel.alpha (+0x28), and its TEST from ccModel.test (+0x30). ccModel::Init (0x0013a440) sets both:

• alpha = alphaBlendTbl[blendType] (0x00348580). blendType is the model header's flag & 3, which Decode_Model keeps at ccModelChunk +0x4c.
• Blend type 0: SetRenderState(1, 1). The alpha test is GEQUAL with AFAIL FB_ONLY, as the port already drew every model.
• Any other type: SetRenderState(1, 0) (0x0013ae60), ATST NEVER with AFAIL FB_ONLY. Every pixel's colour is drawn and no Z is written. It also sets ccModel.flag 0x20.
• ccModel::Draw (0x0013ed70) puts every mmat of a model with flag 0x20 into the sorted group, whatever its transparency.

alphaBlendTbl's first four entries:

The ports drew every model with type 0's state. In title1, 16 of the 97 models are type 1: MDL_xdt_lig_*, the selection glows, and MDL_xdt_dig_*. Mixed instead of added, their black surrounds darkened the screen, which made the square and the box. xddesk01 has no blended model. In stream 2's frame 822, MDL_ngon02 (the figure's glowing runes) is additive over MDL_ngon01.

The fix

• The model's blend type. ModelInfo carries it.
• The state. model_state(blend_type) gives that type's ALPHA and TEST.
• The three draw paths. The desktop's, the title's and the streams' use that state, and put a blended model's mmats in the sorted group.
• The GPU. It draws NEVER with FB_ONLY as a single pass with Z writes off.

Checked

• Unit tests. model_state_by_blend_type checks the four ALPHA values and the two tests. never_fb_only_writes_no_z (piney-gs) draws two additive sprites that add, and a farther opaque one after them that still lands.
• Against the game's code. test_demo_rs.py (18), test_desktop_rs.py (20) and test_desktop_menu_rs.py (5) still pass; the workspace's tests pass, and clippy and fmt are clean.
• Shots. The title menu, on both the GPU and the CPU GS model, now shows a soft glow around the selected item and white text, with no dark boxes.