commit 5ba372fa3e3a51fb69426764f7d5dde395bd4d61
author Nicolas Capens <capn@google.com> Thu Oct 05 16:05:47 2017 -0400
committer Nicolas Capens <nicolascapens@google.com> Fri Oct 06 14:36:10 2017 +0000
tree 6a6db244ed0b25efe645b6bdb9f13e34c311ed09
parent 9d56da27fd2f97af9a5f6a96227abdd5564503cb

Fix depth clamping during 'very' early depth test.

We perform depth testing before computing scanline invariants, as an
optimization. But it was not taking into account that the
fixed-function depth value may require clamping due to the depth bias.

Bug swiftshader:82

Change-Id: I6f8953f9d060c73b5fe209b8cbad70e7cb7588b4
Reviewed-on: https://swiftshader-review.googlesource.com/13088
Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>

src/Renderer/QuadRasterizer.cpp

diff --git a/src/Renderer/QuadRasterizer.cpp b/src/Renderer/QuadRasterizer.cpp
index 2855e16..795e1ee 100644
--- a/src/Renderer/QuadRasterizer.cpp
+++ b/src/Renderer/QuadRasterizer.cpp
@@ -180,7 +180,7 @@
 
 					For(Int x = x0, x < x1, x += 2)
 					{
-						Float4 z = interpolate(xxxx, Dz[0], z, primitive + OFFSET(Primitive,z), false, false);
+						Float4 z = interpolate(xxxx, Dz[0], z, primitive + OFFSET(Primitive,z), false, false, state.depthClamp);
 
 						Float4 zValue;
 
@@ -316,7 +316,7 @@
 		Until(y >= yMax)
 	}
 
-	Float4 QuadRasterizer::interpolate(Float4 &x, Float4 &D, Float4 &rhw, Pointer<Byte> planeEquation, bool flat, bool perspective)
+	Float4 QuadRasterizer::interpolate(Float4 &x, Float4 &D, Float4 &rhw, Pointer<Byte> planeEquation, bool flat, bool perspective, bool clamp)
 	{
 		Float4 interpolant = D;
 
@@ -330,6 +330,11 @@
 			}
 		}
 
+		if(clamp)
+		{
+			interpolant = Min(Max(interpolant, Float4(0.0f)), Float4(1.0f));
+		}
+
 		return interpolant;
 	}
 

src/Renderer/QuadRasterizer.hpp

diff --git a/src/Renderer/QuadRasterizer.hpp b/src/Renderer/QuadRasterizer.hpp
index 5616112..4dfe527 100644
--- a/src/Renderer/QuadRasterizer.hpp
+++ b/src/Renderer/QuadRasterizer.hpp
@@ -49,7 +49,7 @@
 
 		bool interpolateZ() const;
 		bool interpolateW() const;
-		Float4 interpolate(Float4 &x, Float4 &D, Float4 &rhw, Pointer<Byte> planeEquation, bool flat, bool perspective);
+		Float4 interpolate(Float4 &x, Float4 &D, Float4 &rhw, Pointer<Byte> planeEquation, bool flat, bool perspective, bool clamp);
 
 		const PixelProcessor::State &state;
 		const PixelShader *const shader;

src/Shader/PixelRoutine.cpp

diff --git a/src/Shader/PixelRoutine.cpp b/src/Shader/PixelRoutine.cpp
index 90e2073..e681fb4 100644
--- a/src/Shader/PixelRoutine.cpp
+++ b/src/Shader/PixelRoutine.cpp
@@ -94,12 +94,7 @@
 					x -= *Pointer<Float4>(constants + OFFSET(Constants,X) + q * sizeof(float4));
 				}
 
-				z[q] = interpolate(x, Dz[q], z[q], primitive + OFFSET(Primitive,z), false, false);
-
-				if(state.depthClamp)
-				{
-					z[q] = Min(Max(z[q], Float4(0.0f)), Float4(1.0f));
-				}
+				z[q] = interpolate(x, Dz[q], z[q], primitive + OFFSET(Primitive,z), false, false, state.depthClamp);
 			}
 		}
 
@@ -146,7 +141,7 @@
 
 			if(interpolateW())
 			{
-				w = interpolate(xxxx, Dw, rhw, primitive + OFFSET(Primitive,w), false, false);
+				w = interpolate(xxxx, Dw, rhw, primitive + OFFSET(Primitive,w), false, false, false);
 				rhw = reciprocal(w, false, false, true);
 
 				if(state.centroid)
@@ -163,7 +158,7 @@
 					{
 						if(!state.interpolant[interpolant].centroid)
 						{
-							v[interpolant][component] = interpolate(xxxx, Dv[interpolant][component], rhw, primitive + OFFSET(Primitive, V[interpolant][component]), (state.interpolant[interpolant].flat & (1 << component)) != 0, state.perspective);
+							v[interpolant][component] = interpolate(xxxx, Dv[interpolant][component], rhw, primitive + OFFSET(Primitive, V[interpolant][component]), (state.interpolant[interpolant].flat & (1 << component)) != 0, state.perspective, false);
 						}
 						else
 						{
@@ -198,7 +193,7 @@
 
 			if(state.fog.component)
 			{
-				f = interpolate(xxxx, Df, rhw, primitive + OFFSET(Primitive,f), state.fog.flat & 0x01, state.perspective);
+				f = interpolate(xxxx, Df, rhw, primitive + OFFSET(Primitive,f), state.fog.flat & 0x01, state.perspective, false);
 			}
 
 			setBuiltins(x, y, z, w);