From 6a6c5bccdabd15dd1428bb0f5133042c40bfa9fd Mon Sep 17 00:00:00 2001
From: Robert Osfield <robert@openscenegraph.com>
Date: Tue, 14 Jun 2011 10:15:12 +0000
Subject: [PATCH] Added GLBufferObject::computeBufferAlignment(..) method to
 enable buffer entries to be aligned along specified buffer alignment
 boundaries, currently defaulting to 4.

---
 include/osg/BufferObject |  7 +++++++
 src/osg/BufferObject.cpp | 10 +++++++---
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/include/osg/BufferObject b/include/osg/BufferObject
index d1315035d..5c3e243a1 100644
--- a/include/osg/BufferObject
+++ b/include/osg/BufferObject
@@ -334,6 +334,13 @@ class OSG_EXPORT GLBufferObject : public Referenced
 
         virtual ~GLBufferObject();
 
+        unsigned int computeBufferAlignment(unsigned int pos, unsigned int bufferAlignment) const
+        {
+            if (bufferAlignment<2) return pos;
+            if ((pos%bufferAlignment)==0) return pos;
+            return ((pos/bufferAlignment)+1)*bufferAlignment;
+        }
+
         unsigned int            _contextID;
         GLuint                  _glObjectID;
 
diff --git a/src/osg/BufferObject.cpp b/src/osg/BufferObject.cpp
index 3aea3eaac..c51079c67 100644
--- a/src/osg/BufferObject.cpp
+++ b/src/osg/BufferObject.cpp
@@ -110,6 +110,8 @@ void GLBufferObject::compileBuffer()
     bool compileAll = false;
     bool offsetChanged = false;
 
+    unsigned int bufferAlignment = 4;
+
     unsigned int newTotalSize = 0;
     unsigned int i=0;
     for(; i<_bufferObject->getNumBufferData(); ++i)
@@ -122,7 +124,7 @@ void GLBufferObject::compileBuffer()
                 entry.dataSource != bd ||
                 entry.dataSize != bd->getTotalDataSize())
             {
-                unsigned int previousEndOfBufferDataMarker = entry.offset + entry.dataSize;
+                unsigned int previousEndOfBufferDataMarker = computeBufferAlignment(entry.offset + entry.dataSize, bufferAlignment);
 
                 // OSG_NOTICE<<"GLBufferObject::compileBuffer(..) updating BufferEntry"<<std::endl;
 
@@ -139,7 +141,9 @@ void GLBufferObject::compileBuffer()
                 }
             }
             else
-                newTotalSize += entry.dataSize;
+            {
+                newTotalSize = computeBufferAlignment(newTotalSize + entry.dataSize, bufferAlignment);
+            }
         }
         else
         {
@@ -155,7 +159,7 @@ void GLBufferObject::compileBuffer()
             OSG_NOTICE<<"   dataSource "<<entry.dataSource<<std::endl;
             OSG_NOTICE<<"   modifiedCount "<<entry.modifiedCount<<std::endl;
 #endif
-            newTotalSize += entry.dataSize;
+            newTotalSize = computeBufferAlignment(newTotalSize + entry.dataSize, bufferAlignment);
 
             _bufferEntries.push_back(entry);
         }