Clamp blend factors and color output
The spec requires that input to the blending stage is clamped to the
range of the color attachment's format.
The clamp that was performed at the end of blending has been moved to
the color write method. Only VK_FORMAT_B10G11R11_UFLOAT_PACK32 was
previously affected by that, but it already has a clamp in the
r11g11b10Pack() function.
These changes prepare for handling normalized formats in the floating-
point code path.
Bug: b/204322086
Change-Id: I7eba90afb98c8aace93ddabb3168f6752e0d4f31
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/58789
Tested-by: Nicolas Capens <nicolascapens@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
diff --git a/src/Pipeline/PixelRoutine.cpp b/src/Pipeline/PixelRoutine.cpp
index 3cad2f5..9ea0bd6 100644
--- a/src/Pipeline/PixelRoutine.cpp
+++ b/src/Pipeline/PixelRoutine.cpp
@@ -2258,6 +2258,25 @@
default:
UNSUPPORTED("VkBlendFactor: %d", int(colorBlendFactor));
}
+
+ // "If the color attachment is fixed-point, the components of the source and destination values and blend factors are each clamped
+ // to [0,1] or [-1,1] respectively for an unsigned normalized or signed normalized color attachment prior to evaluating the blend
+ // operations. If the color attachment is floating-point, no clamping occurs."
+ if(blendFactorCanExceedFormatRange(colorBlendFactor, format))
+ {
+ if(format.isUnsignedNormalized())
+ {
+ blendFactor.x = Min(Max(blendFactor.x, Float4(0.0f)), Float4(1.0f));
+ blendFactor.y = Min(Max(blendFactor.y, Float4(0.0f)), Float4(1.0f));
+ blendFactor.z = Min(Max(blendFactor.z, Float4(0.0f)), Float4(1.0f));
+ }
+ else if(format.isSignedNormalized())
+ {
+ blendFactor.x = Min(Max(blendFactor.x, Float4(-1.0f)), Float4(1.0f));
+ blendFactor.y = Min(Max(blendFactor.y, Float4(-1.0f)), Float4(1.0f));
+ blendFactor.z = Min(Max(blendFactor.z, Float4(-1.0f)), Float4(1.0f));
+ }
+ }
}
void PixelRoutine::blendFactorAlpha(Float4 &blendFactorAlpha, const Float4 &sourceAlpha, const Float4 &destAlpha, VkBlendFactor alphaBlendFactor, vk::Format format)
@@ -2308,6 +2327,58 @@
default:
UNSUPPORTED("VkBlendFactor: %d", int(alphaBlendFactor));
}
+
+ // "If the color attachment is fixed-point, the components of the source and destination values and blend factors are each clamped
+ // to [0,1] or [-1,1] respectively for an unsigned normalized or signed normalized color attachment prior to evaluating the blend
+ // operations. If the color attachment is floating-point, no clamping occurs."
+ if(blendFactorCanExceedFormatRange(alphaBlendFactor, format))
+ {
+ if(format.isUnsignedNormalized())
+ {
+ blendFactorAlpha = Min(Max(blendFactorAlpha, Float4(0.0f)), Float4(1.0f));
+ }
+ else if(format.isSignedNormalized())
+ {
+ blendFactorAlpha = Min(Max(blendFactorAlpha, Float4(-1.0f)), Float4(1.0f));
+ }
+ }
+}
+
+bool PixelRoutine::blendFactorCanExceedFormatRange(VkBlendFactor blendFactor, vk::Format format)
+{
+ switch(blendFactor)
+ {
+ case VK_BLEND_FACTOR_ZERO:
+ case VK_BLEND_FACTOR_ONE:
+ return false;
+ case VK_BLEND_FACTOR_SRC_COLOR:
+ case VK_BLEND_FACTOR_SRC_ALPHA:
+ // Source values have been clamped after fragment shader execution if the attachment format is normalized.
+ return false;
+ case VK_BLEND_FACTOR_DST_COLOR:
+ case VK_BLEND_FACTOR_DST_ALPHA:
+ // Dest values have a valid range due to being read from the attachment.
+ return false;
+ case VK_BLEND_FACTOR_ONE_MINUS_SRC_COLOR:
+ case VK_BLEND_FACTOR_ONE_MINUS_SRC_ALPHA:
+ case VK_BLEND_FACTOR_ONE_MINUS_DST_COLOR:
+ case VK_BLEND_FACTOR_ONE_MINUS_DST_ALPHA:
+ // For signed formats, negative values cause the result to exceed 1.0.
+ return format.isSignedNormalized();
+ case VK_BLEND_FACTOR_SRC_ALPHA_SATURATE:
+ // min(As, 1 - Ad)
+ return false;
+ case VK_BLEND_FACTOR_CONSTANT_COLOR:
+ case VK_BLEND_FACTOR_CONSTANT_ALPHA:
+ case VK_BLEND_FACTOR_ONE_MINUS_CONSTANT_COLOR:
+ case VK_BLEND_FACTOR_ONE_MINUS_CONSTANT_ALPHA:
+ // TODO(b/204546345): Use pre-clamped blend constants.
+ return true;
+
+ default:
+ UNSUPPORTED("VkBlendFactor: %d", int(blendFactor));
+ return true;
+ }
}
Vector4f PixelRoutine::alphaBlend(int index, const Pointer<Byte> &cBuffer, const Vector4f &sourceColor, const Int &x)
@@ -2511,17 +2582,31 @@
UNSUPPORTED("VkBlendOp: %d", int(state.blendState[index].blendOperationAlpha));
}
- if(format.isUnsignedComponent(0)) { blendedColor.x = Max(blendedColor.x, Float4(0.0f)); }
- if(format.isUnsignedComponent(1)) { blendedColor.y = Max(blendedColor.y, Float4(0.0f)); }
- if(format.isUnsignedComponent(2)) { blendedColor.z = Max(blendedColor.z, Float4(0.0f)); }
- if(format.isUnsignedComponent(3)) { blendedColor.w = Max(blendedColor.w, Float4(0.0f)); }
-
return blendedColor;
}
void PixelRoutine::writeColor(int index, const Pointer<Byte> &cBuffer, const Int &x, Vector4f &color, const Int &sMask, const Int &zMask, const Int &cMask)
{
vk::Format format = state.colorFormat[index];
+ switch(format)
+ {
+ default:
+ // TODO(b/204560089): Omit clamp if redundant
+ if(format.isUnsignedNormalized())
+ {
+ color.x = Min(Max(color.x, Float4(0.0f)), Float4(1.0f));
+ color.y = Min(Max(color.y, Float4(0.0f)), Float4(1.0f));
+ color.z = Min(Max(color.z, Float4(0.0f)), Float4(1.0f));
+ color.w = Min(Max(color.w, Float4(0.0f)), Float4(1.0f));
+ }
+ else if(format.isSignedNormalized())
+ {
+ color.x = Min(Max(color.x, Float4(-1.0f)), Float4(1.0f));
+ color.y = Min(Max(color.y, Float4(-1.0f)), Float4(1.0f));
+ color.z = Min(Max(color.z, Float4(-1.0f)), Float4(1.0f));
+ color.w = Min(Max(color.w, Float4(-1.0f)), Float4(1.0f));
+ }
+ }
switch(format)
{
diff --git a/src/Pipeline/PixelRoutine.hpp b/src/Pipeline/PixelRoutine.hpp
index 956f230..3b13ac1 100644
--- a/src/Pipeline/PixelRoutine.hpp
+++ b/src/Pipeline/PixelRoutine.hpp
@@ -79,6 +79,7 @@
void readPixel(int index, const Pointer<Byte> &cBuffer, const Int &x, Vector4s &pixel);
void blendFactorRGB(Vector4f &blendFactorRGB, const Vector4f &sourceColor, const Vector4f &destColor, VkBlendFactor colorBlendFactor, vk::Format format);
void blendFactorAlpha(Float4 &blendFactorAlpha, const Float4 &sourceAlpha, const Float4 &destAlpha, VkBlendFactor alphaBlendFactor, vk::Format format);
+ bool blendFactorCanExceedFormatRange(VkBlendFactor blendFactor, vk::Format format);
void writeStencil(Pointer<Byte> &sBuffer, const Int &x, const Int sMask[4], const Int zMask[4], const Int cMask[4], const SampleSet &samples);
void writeDepth(Pointer<Byte> &zBuffer, const Int &x, const Int zMask[4], const SampleSet &samples);
void occlusionSampleCount(const Int zMask[4], const Int sMask[4], const SampleSet &samples);
