Fix culling to match Vulkan convention

Correct the sign of the area calculation. The front facing determination can then be written to exactly match the spec -- CCW means positive area is front facing. Change-Id: Ibed3e26b0cf77030325044c7dc9e818264a8750d Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/26009Tested-by: Chris Forbes <chrisforbes@google.com> Reviewed-by: Nicolas Capens <nicolascapens@google.com>

Fix culling to match Vulkan convention
bb305299 · Chris Forbes · 823ca854 · bb305299
Commit bb305299 authored Mar 01, 2019 by Chris Forbes
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SetupRoutine.cpp src/Pipeline/SetupRoutine.cpp +1 -1

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--- a/src/Pipeline/SetupRoutine.cpp
+++ b/src/Pipeline/SetupRoutine.cpp
@@ -83,7 +83,7 @@ namespace sw
 				Float y1 = Float(Y[1]);
 				Float y2 = Float(Y[2]);

-				Float A = (y2 - y0) * x1 + (y1 - y2) * x0 + (y0 - y1) * x2;   // Area
+				Float A = (y0 - y2) * x1 + (y2 - y1) * x0 + (y1 - y0) * x2;   // Area

 				If(A == 0.0f)
 				{