From 51a4d6a4bef09e7b270ee26e5b2889379819da45 Mon Sep 17 00:00:00 2001
From: Jules Blok <jules.blok@gmail.com>
Date: Tue, 4 Nov 2014 01:12:00 +0100
Subject: [PATCH] GeometryShader: Adjust positions after projection.

By adjusting the positions in clip space we can avoid the re-projection.
---
 Source/Core/VideoCommon/GeometryShaderGen.cpp   | 13 ++-----------
 Source/Core/VideoCommon/VertexShaderGen.cpp     |  8 +-------
 Source/Core/VideoCommon/VertexShaderManager.cpp |  4 ++--
 3 files changed, 5 insertions(+), 20 deletions(-)

diff --git a/Source/Core/VideoCommon/GeometryShaderGen.cpp b/Source/Core/VideoCommon/GeometryShaderGen.cpp
index 8260ed5f05..d116dfe39a 100644
--- a/Source/Core/VideoCommon/GeometryShaderGen.cpp
+++ b/Source/Core/VideoCommon/GeometryShaderGen.cpp
@@ -77,25 +77,16 @@ static inline void GenerateGeometryShader(T& out, u32 components, API_TYPE ApiTy
 		out.Write("\tfor (layer = 0; layer < %d; ++layer) {\n", g_ActiveConfig.iStereoMode > 0 ? 2 : 1);
 
 	out.Write("\tgl_Layer = layer;\n");
-	out.Write("\tvec4 stereoproj = " I_PROJECTION"[0];\n");
-	out.Write("\tstereoproj[2] += " I_STEREOOFFSET"[layer] * stereoproj[0];\n");
 
 	out.Write("\tfor (int i = 0; i < gl_in.length(); ++i) {\n");
 	out.Write("\t\to = v[i];\n");
 
 	if (g_ActiveConfig.iStereoMode > 0)
-		out.Write("\t\to.pos = float4(dot(stereoproj, v[i].rawpos), dot(" I_PROJECTION"[1], v[i].rawpos), dot(" I_PROJECTION"[2], v[i].rawpos), dot(" I_PROJECTION"[3], v[i].rawpos)); \n");
-
-	if (ApiType == API_D3D)
 	{
-		out.Write("\t\to.pos.z = " I_DEPTHPARAMS".x * o.pos.w + o.pos.z * " I_DEPTHPARAMS".y;\n");
-	}
-	else // OGL
-	{
-		out.Write("\t\to.pos.z = o.pos.w + o.pos.z * 2.0;\n");
+		out.Write("\t\to.clipPos.x += o.clipPos.w * " I_STEREOOFFSET"[layer] * " I_PROJECTION"[0][0];\n");
+		out.Write("\t\to.pos.x += o.pos.w * " I_STEREOOFFSET"[layer] * " I_PROJECTION"[0][0];\n");
 	}
 
-	out.Write("\t\to.pos.xy = o.pos.xy - " I_DEPTHPARAMS".zw;\n");
 	out.Write("\t\tgl_Position = o.pos;\n");
 	out.Write("\t\tEmitVertex();\n");
 	out.Write("\t}\n");
diff --git a/Source/Core/VideoCommon/VertexShaderGen.cpp b/Source/Core/VideoCommon/VertexShaderGen.cpp
index fd2ee7f3e6..700bd0d2a6 100644
--- a/Source/Core/VideoCommon/VertexShaderGen.cpp
+++ b/Source/Core/VideoCommon/VertexShaderGen.cpp
@@ -52,9 +52,6 @@ static inline void GenerateVSOutputStruct(T& object, API_TYPE api_type)
 	if (g_ActiveConfig.bEnablePixelLighting)
 		DefineVSOutputStructMember(object, api_type, "float4", "Normal", -1, "TEXCOORD", xfmem.numTexGen.numTexGens + 1);
 
-	if (g_ActiveConfig.iStereoMode > 0)
-		DefineVSOutputStructMember(object, api_type, "float4", "rawpos", -1, "POSITION");
-
 	object.Write("};\n");
 }
 
@@ -125,6 +122,7 @@ static inline void GenerateVertexShader(T& out, u32 components, API_TYPE api_typ
 				out.Write("in float%d tex%d; // ATTR%d,\n", hastexmtx ? 3 : 2, i, SHADER_TEXTURE0_ATTRIB + i);
 		}
 
+		uid_data->stereo = g_ActiveConfig.iStereoMode > 0;
 		out.Write("centroid out VS_OUTPUT %s;\n", (g_ActiveConfig.iStereoMode > 0) ? "v" : "o");
 
 		out.Write("void main()\n{\n");
@@ -205,10 +203,6 @@ static inline void GenerateVertexShader(T& out, u32 components, API_TYPE api_typ
 
 	out.Write("o.pos = float4(dot(" I_PROJECTION"[0], pos), dot(" I_PROJECTION"[1], pos), dot(" I_PROJECTION"[2], pos), dot(" I_PROJECTION"[3], pos));\n");
 
-	uid_data->stereo = g_ActiveConfig.iStereoMode > 0;
-	if (g_ActiveConfig.iStereoMode > 0)
-		out.Write("o.rawpos = pos;\n");
-
 	out.Write("int4 lacc;\n"
 			"float3 ldir, h;\n"
 			"float dist, dist2, attn;\n");
diff --git a/Source/Core/VideoCommon/VertexShaderManager.cpp b/Source/Core/VideoCommon/VertexShaderManager.cpp
index 150bd783a8..f6d285cffd 100644
--- a/Source/Core/VideoCommon/VertexShaderManager.cpp
+++ b/Source/Core/VideoCommon/VertexShaderManager.cpp
@@ -516,8 +516,8 @@ void VertexShaderManager::SetConstants()
 		if (g_ActiveConfig.iStereoMode > 0 && xfmem.projection.type == GX_PERSPECTIVE)
 		{
 			float offset = g_ActiveConfig.iStereoSeparation / (200.0f * g_ActiveConfig.iStereoFocalLength);
-			constants.stereooffset[0] = (g_ActiveConfig.bStereoSwapEyes) ? -offset : offset;
-			constants.stereooffset[1] = (g_ActiveConfig.bStereoSwapEyes) ? offset : -offset;
+			constants.stereooffset[0] = (g_ActiveConfig.bStereoSwapEyes) ? offset : -offset;
+			constants.stereooffset[1] = (g_ActiveConfig.bStereoSwapEyes) ? -offset : offset;
 		}
 		else
 		{