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Reinterpret between 16- and 32-bit framebuffers by PSP pixel at higher render scales

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The 16-to-32-bit reinterpret sampled a quarter texel either side of the
render pixel, which only lands in the two 16-bit halves of a 32-bit pixel at
1x: at 3x, two of every three render pixels took both halves from the same
16-bit pixel. The 32-to-16-bit one picked the half by render pixel too. Now
both go by the PSP pixel. Cars Race-O-Rama rewrites its 8888 frame through
565 views in 16-pixel columns, and drew vertical stripes at 2x and up
(#15914); now it renders like 1x. Nothing changes at 1x.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
This commit is contained in:
Henrik RydgårdandClaude Opus 5.5 committed 2026-10-09 17:01:37 +02:00
1 parent a9b18a9192
commit e896203f32
1 file changed
+7 -3
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GPU/Common/ReinterpretFramebuffer.cpp
+7 -3
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@@ -165,8 +165,11 @@ Draw2DPipelineInfo GenerateReinterpretFragmentShader(ShaderWriter &writer, GEBuf
} else if (IsBufferFormat16Bit(from) && !IsBufferFormat16Bit(to)) {
// 16-to-32-bit (two pixels, draw size is halved)
writer.C(" vec4 valLeft = ").SampleTexture2D("tex", "v_texcoord.xy + vec2(-0.25 / texSize.x, 0.0)").C(";\n");
writer.C(" vec4 valRight = ").SampleTexture2D("tex", "v_texcoord.xy + vec2(0.25 / texSize.x, 0.0)").C(";\n");
// The two 16-bit pixels of the PSP pixel this is in, at their centers: at a higher render scale, the render
// pixels around this one's can both be in the same 16-bit pixel.
writer.C(" float pspX = floor(v_texcoord.x * texSize.x / (2.0 * scaleFactor));\n");
writer.C(" vec4 valLeft = ").SampleTexture2D("tex", "vec2((2.0 * pspX + 0.5) * scaleFactor / texSize.x, v_texcoord.y)").C(";\n");
writer.C(" vec4 valRight = ").SampleTexture2D("tex", "vec2((2.0 * pspX + 1.5) * scaleFactor / texSize.x, v_texcoord.y)").C(";\n");
writer.C(" vec4 outColor = unpackColor(packColor(valLeft), packColor(valRight));\n");
_assert_("not yet implemented");
@@ -174,7 +177,8 @@ Draw2DPipelineInfo GenerateReinterpretFragmentShader(ShaderWriter &writer, GEBuf
// 32-to-16-bit (half of the pixel, draw size is doubled).
writer.C(" vec4 val = ").SampleTexture2D("tex", "v_texcoord.xy").C(";\n");
writer.C(" float u = mod(floor(v_texcoord.x * texSize.x * 2.0), 2.0);\n");
// Which half, by the 16-bit PSP pixel this is in (not the render pixel).
writer.C(" float u = mod(floor(v_texcoord.x * texSize.x * 2.0 / scaleFactor), 2.0);\n");
writer.C(" vec4 outColor = unpackColor(u == 0.0 ? packColor(val.rg) : packColor(val.ba));\n");
}