Entry 146

REGION_REPEAT in the GPU renderer: the stream shades' blocks

2026-09-26render

Filescrates/piney-gs/src/convert.rscrates/piney-gs/src/lib.rscrates/piney-draw/src/lib.rsdocs/engine/stream.md

A GAPS drawing item. Stream 15's shades (ccBufferSampling::SetShade(t, z, colour)) read the picture being drawn with CLAMP_1 set to REGION_REPEAT. The mask is 1024 - t and the fix t / 2, so every t x t block reads one texel and the far scene turns blocky behind the figures. The software rasterizer read Wrap::Region that way. piney-gs, the renderer the game runs on, sampled it as a plain repeat, so there the shades were smooth.

The change

• The vertex. A 2D primitive whose texture wraps by region gets a new Params::REGION bit and the mask and fix in GVertex::region, as a new flat vertex attribute.
• The shader. With the bit set, it takes the texel under the pixel, masks and fixes both coordinates as the GS does, and fetches that texel (textureLoad, unfiltered) in place of the sample.
• The check. region_repeat_reads_in_blocks draws eight one-texel columns of rising red, copies them, and draws the copy with mask 1024 - 4 and fix 2. The eight pixels read columns 2 and 6, four each, as the GS reads them.