commit 5491cb48df1edf37f75b36214f0e8aa3a7d6dbc1
author Nicolas Capens <capn@google.com> Thu Jul 02 15:33:29 2015 -0400
committer Nicolas Capens <capn@google.com> Fri Jul 03 15:10:05 2015 +0000
tree d85af3deda0736e7b452b22b8c1e457963660c01
parent 83d0e98ed94db02a7b8b13b91c68e597e17124cb

Eliminate the half-pixel NDC shift.

Bug 22123818

Change-Id: If9bf78d6b44ccd0662676c8896837cca8829efc8
Reviewed-on: https://swiftshader-review.googlesource.com/3624
Tested-by: Nicolas Capens <capn@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>

src/Renderer/Clipper.cpp

diff --git a/src/Renderer/Clipper.cpp b/src/Renderer/Clipper.cpp
index 246ec2f..e2bb617 100644
--- a/src/Renderer/Clipper.cpp
+++ b/src/Renderer/Clipper.cpp
@@ -166,8 +166,8 @@
 		{
 			int j = i == polygon.n - 1 ? 0 : i + 1;
 
-			float di = V[i]->w + (V[i]->x + data.halfPixelX[0] * V[i]->w);
-			float dj = V[j]->w + (V[j]->x + data.halfPixelX[0] * V[j]->w);
+			float di = V[i]->w + V[i]->x;
+			float dj = V[j]->w + V[j]->x;
 
 			if(di >= 0)
 			{
@@ -208,8 +208,8 @@
 		{
 			int j = i == polygon.n - 1 ? 0 : i + 1;
 
-			float di = V[i]->w - (V[i]->x + data.halfPixelX[0] * V[i]->w);
-			float dj = V[j]->w - (V[j]->x + data.halfPixelX[0] * V[j]->w);
+			float di = V[i]->w - V[i]->x;
+			float dj = V[j]->w - V[j]->x;
 
 			if(di >= 0)
 			{
@@ -250,8 +250,8 @@
 		{
 			int j = i == polygon.n - 1 ? 0 : i + 1;
 
-			float di = V[i]->w - (V[i]->y + data.halfPixelY[0] * V[i]->w);
-			float dj = V[j]->w - (V[j]->y + data.halfPixelY[0] * V[j]->w);
+			float di = V[i]->w - V[i]->y;
+			float dj = V[j]->w - V[j]->y;
 
 			if(di >= 0)
 			{
@@ -292,8 +292,8 @@
 		{
 			int j = i == polygon.n - 1 ? 0 : i + 1;
 
-			float di = V[i]->w + (V[i]->y + data.halfPixelY[0] * V[i]->w);
-			float dj = V[j]->w + (V[j]->y + data.halfPixelY[0] * V[j]->w);
+			float di = V[i]->w + V[i]->y;
+			float dj = V[j]->w + V[j]->y;
 
 			if(di >= 0)
 			{