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allightmapblur_gl_test compares the dispatch with the fragment passes in single precision, past AMD's 8-bit export rounding #554

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Merged
RyeMutt merged 1 commit into from
Oct 23, 2026
Merged

allightmapblur_gl_test compares the dispatch with the fragment passes in single precision, past AMD's 8-bit export rounding #554

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29 changes: 20 additions & 9 deletions indra/alrender/tests/allightmapblur_gl_scene.h
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Original file line number Diff line number Diff line change
Expand Up @@ -95,7 +95,7 @@ namespace allightmapblur_gl
mFragment.unload();
mCompute.unload();
mShaders.clearShaderObjects();
for (LLRenderTarget* target : { &mGBuffer, &mLight, &mScratch, &mFloatScratch, &mComputeLight, &mBlurred })
for (LLRenderTarget* target : { &mGBuffer, &mLight, &mScratch, &mFloatScratch, &mFloatLight, &mComputeLight, &mBlurred })
{
target->release();
}
Expand Down Expand Up @@ -229,8 +229,9 @@ namespace allightmapblur_gl
REQUIRE(mGBuffer.ensure(gbuffer) == LLRenderTarget::EnsureResult::Built);
REQUIRE(mLight.ensure(light, mGBuffer) == LLRenderTarget::EnsureResult::Built);
REQUIRE(mScratch.ensure(light, mGBuffer) == LLRenderTarget::EnsureResult::Built);
REQUIRE(mFloatScratch.ensure({ .width = w, .height = h, .color = { GL_RGBA32F } }, mGBuffer) ==
LLRenderTarget::EnsureResult::Built);
const ALRenderTargetDesc single{ .width = w, .height = h, .color = { GL_RGBA32F } };
REQUIRE(mFloatScratch.ensure(single, mGBuffer) == LLRenderTarget::EnsureResult::Built);
REQUIRE(mFloatLight.ensure(single, mGBuffer) == LLRenderTarget::EnsureResult::Built);
REQUIRE(mComputeLight.ensure(light, mGBuffer) == LLRenderTarget::EnsureResult::Built);
REQUIRE(mBlurred.ensure({ .width = w, .height = h, .color = { GL_RG8 } }) == LLRenderTarget::EnsureResult::Built);

Expand Down Expand Up @@ -320,11 +321,20 @@ namespace allightmapblur_gl
}

// renderDeferredLighting's two passes: across into the scratch, cleared white as the sun pass clears the map,
// and down from it back into the map, each over geometry alone. Through a single-precision scratch, the
// fragment passes keep between the axes what the dispatch keeps in shared memory.
void blurFragment(const ALLightMapBlur::Kernel& kernel, bool float_scratch = false)
// and down from it back into the map, each over geometry alone. In single precision, through a scratch and
// into a copy of the light map (mFloatLight), the fragment passes keep between the axes what the dispatch keeps
// in shared memory, and leave unrounded what its store rounds to 8 bits: an 8-bit target need not round as the
// store does, and AMD's driver hands one the colour at half precision, rounded toward zero, so about one texel
// in twenty comes out a step lower.
void blurFragment(const ALLightMapBlur::Kernel& kernel, bool in_float = false)
{
LLRenderTarget& scratch = float_scratch ? mFloatScratch : mScratch;
LLRenderTarget& scratch = in_float ? mFloatScratch : mScratch;
LLRenderTarget& light = in_float ? mFloatLight : mLight;
if (in_float)
{
// The sky keeps the light map's texels.
ll_test::writeTexture(mFloatLight.getTexture(), mW, mH, GL_RGBA, GL_FLOAT, read(mLight).data());
}
scratch.bindTarget();
gGL.setClearColor(LLColor4::white);
scratch.clear(GL_COLOR_BUFFER_BIT);
Expand All @@ -340,15 +350,15 @@ namespace allightmapblur_gl
scratch.flush();

bindDeferred(mFragment, scratch, kernel);
mLight.bindTarget();
light.bindTarget();
mFragment.uniform2f(LLShaderMgr::DELTA, 0.f, 1.f);
{
LLGLDisable blend(GL_BLEND);
ALDrawnOnly drawn;
mTriangle->setBuffer();
mTriangle->drawArrays(LLRender::TRIANGLES, 0, 3);
}
mLight.flush();
light.flush();
mFragment.unbind();
}

Expand Down Expand Up @@ -527,6 +537,7 @@ namespace allightmapblur_gl
LLRenderTarget mLight;
LLRenderTarget mScratch;
LLRenderTarget mFloatScratch;
LLRenderTarget mFloatLight;
LLRenderTarget mComputeLight;
LLRenderTarget mBlurred;
LLPointer<LLVertexBuffer> mTriangle;
Expand Down
7 changes: 5 additions & 2 deletions indra/alrender/tests/allightmapblur_gl_test.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -134,15 +134,18 @@ TEST_CASE_METHOD(Scene, "allightmapblur_gl: one dispatch blurs texel for texel a
poisonBlurred();
REQUIRE(blurCompute(kernel));

const std::vector<F32> fragment = read(mLight);
// The dispatch's store holds the 8 bits nearest the fragment passes' single precision, or at a tie, which their
// value lies within a rounding of at a few texels, either of the two.
const std::vector<F32> fragment = read(mFloatLight);
const std::vector<F32> compute = read(mBlurred);
const auto nearest = [](F32 stored, F32 value) { return std::fabs(stored - value) * 255.f <= 0.5f + 1e-4f; };
S32 differ = 0;
for (S32 y = 0; y < H; ++y)
{
for (S32 x = 0; x < W; ++x)
{
const size_t i = (size_t(y) * W + x) * 4;
if (compute[i] != fragment[i] || compute[i + 1] != fragment[i + 1])
if (!nearest(compute[i], fragment[i]) || !nearest(compute[i + 1], fragment[i + 1]))
{
if (++differ <= 8)
{
Expand Down
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