From d54daa19a08713dd6ff188f1ff2a285c2c43d82f Mon Sep 17 00:00:00 2001
From: Shyotl <Shyotl@gmail.com>
Date: Fri, 9 Nov 2012 18:10:39 -0600
Subject: [PATCH] Allow trial of trasform feedback (for testing/benchmark) on
 hardware that declares support for GL_EXT_transform_feedback. Performance is
 far less than satisfactory on my hd4870(ogl3.3 gpu), however. Also messes up
 texcoords. Don't add RenderUseTransformFeedback to settings.xml.

---
 indra/llrender/llgl.cpp           |  2 +-
 indra/llrender/llvertexbuffer.cpp | 10 ++++++++++
 indra/llrender/llvertexbuffer.h   |  6 +++++-
 indra/newview/llface.cpp          |  2 +-
 4 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/indra/llrender/llgl.cpp b/indra/llrender/llgl.cpp
index 762571adc..ea43ac5c0 100644
--- a/indra/llrender/llgl.cpp
+++ b/indra/llrender/llgl.cpp
@@ -935,7 +935,7 @@ void LLGLManager::initExtensions()
 	mHasBlendFuncSeparate = ExtensionExists("GL_EXT_blend_func_separate", gGLHExts.mSysExts);
 	mHasTextureRectangle = ExtensionExists("GL_ARB_texture_rectangle", gGLHExts.mSysExts);
 	mHasDebugOutput = ExtensionExists("GL_ARB_debug_output", gGLHExts.mSysExts);
-	mHasTransformFeedback = mGLVersion >= 4.f ? TRUE : FALSE;
+	mHasTransformFeedback = mGLVersion >= 4.f || ExtensionExists("GL_EXT_transform_feedback", gGLHExts.mSysExts);
 #if !LL_DARWIN
 	mHasPointParameters = !mIsATI && ExtensionExists("GL_ARB_point_parameters", gGLHExts.mSysExts);
 #endif
diff --git a/indra/llrender/llvertexbuffer.cpp b/indra/llrender/llvertexbuffer.cpp
index bc4c201d9..3f6cd6227 100644
--- a/indra/llrender/llvertexbuffer.cpp
+++ b/indra/llrender/llvertexbuffer.cpp
@@ -2083,6 +2083,16 @@ void LLVertexBuffer::flush()
 	}
 }
 
+// bind for transform feedback (quick 'n dirty)
+void LLVertexBuffer::bindForFeedback(U32 channel, U32 type, U32 index, U32 count)
+{
+#if GL_TRANSFORM_FEEDBACK_BUFFER
+	U32 offset = mOffsets[type] + sTypeSize[type]*index;
+	U32 size= (sTypeSize[type]*count);
+	glBindBufferRange(GL_TRANSFORM_FEEDBACK_BUFFER, channel, mGLBuffer, offset, size);
+#endif
+}
+
 // Set for rendering
 void LLVertexBuffer::setBuffer(U32 data_mask)
 {
diff --git a/indra/llrender/llvertexbuffer.h b/indra/llrender/llvertexbuffer.h
index 469acfcef..0fab69cbc 100644
--- a/indra/llrender/llvertexbuffer.h
+++ b/indra/llrender/llvertexbuffer.h
@@ -39,6 +39,7 @@
 #include <list>
 
 #define LL_MAX_VERTEX_ATTRIB_LOCATION 64
+#define GL_TRANSFORM_FEEDBACK_BUFFER
 
 //============================================================================
 // NOTES
@@ -202,16 +203,18 @@ protected:
 	void 	destroyGLIndices();
 	void	updateNumVerts(S32 nverts);
 	void	updateNumIndices(S32 nindices); 
-	bool	useVBOs() const;
 	void	unmapBuffer();
 		
 public:
+
 	LLVertexBuffer(U32 typemask, S32 usage);
 	
 	// map for data access
 	volatile U8*		mapVertexBuffer(S32 type, S32 index, S32 count, bool map_range);
 	volatile U8*		mapIndexBuffer(S32 index, S32 count, bool map_range);
 
+	void bindForFeedback(U32 channel, U32 type, U32 index, U32 count);
+
 	// set for rendering
 	virtual void	setBuffer(U32 data_mask); 	// calls  setupVertexBuffer() if data_mask is not 0
 	void flush(); //flush pending data to GL memory
@@ -240,6 +243,7 @@ public:
 	bool getClothWeightStrider(LLStrider<LLVector4>& strider, S32 index=0, S32 count = -1, bool map_range = false);
 	
 
+	bool	useVBOs() const;
 	bool isEmpty() const					{ return mEmpty; }
 	bool isLocked() const					{ return mVertexLocked || mIndexLocked; }
 	S32 getNumVerts() const					{ return mNumVerts; }
diff --git a/indra/newview/llface.cpp b/indra/newview/llface.cpp
index d1e0e3c52..277f1bb34 100644
--- a/indra/newview/llface.cpp
+++ b/indra/newview/llface.cpp
@@ -1374,7 +1374,7 @@ BOOL LLFace::getGeometryVolume(const LLVolume& volume,
 	
 	static LLCachedControl<bool> use_transform_feedback("RenderUseTransformFeedback", false);
 
-#if 0//#ifdef GL_TRANSFORM_FEEDBACK_BUFFER
+#ifdef GL_TRANSFORM_FEEDBACK_BUFFER
 	if (use_transform_feedback &&
 		gTransformPositionProgram.mProgramObject && //transform shaders are loaded
 		mVertexBuffer->useVBOs() && //target buffer is in VRAM