From 7269f71c477bf06efe0810c29bd3933cc23fff27 Mon Sep 17 00:00:00 2001
From: Paul MARTZ <pmartz@skew-matrix.com>
Date: Wed, 21 Oct 2009 21:45:55 +0000
Subject: [PATCH] Add CMake-controllable option to avoid doing a
 glBlitFramebuffer into depth to resolve multisampling. This works arouns a
 hang on OS X with NVIDIA GeForce 8800 and v1.5.49 drivers.

---
 src/osgUtil/CMakeLists.txt  | 10 ++++++++++
 src/osgUtil/RenderStage.cpp |  7 +++++++
 2 files changed, 17 insertions(+)

diff --git a/src/osgUtil/CMakeLists.txt b/src/osgUtil/CMakeLists.txt
index c79cbe5d2..603099991 100644
--- a/src/osgUtil/CMakeLists.txt
+++ b/src/osgUtil/CMakeLists.txt
@@ -6,6 +6,16 @@ ELSE (DYNAMIC_OPENSCENEGRAPH)
     ADD_DEFINITIONS(-DOSG_LIBRARY_STATIC)
 ENDIF(DYNAMIC_OPENSCENEGRAPH)
 
+
+#
+# MSFBO resolve blit to depth buffer control.
+#
+OPTION(OSG_MULTISAMPLE_FBO_RESOLVE_IGNORES_DEPTH "Set to ON to ignore depth when resolving multisampled FBO rendering. This is a workaround for a crash on OS X with NVIDIA driver 1.5.49." OFF)
+IF(OSG_MULTISAMPLE_FBO_RESOLVE_IGNORES_DEPTH)
+    ADD_DEFINITIONS(-DOSG_MULTISAMPLE_FBO_RESOLVE_IGNORES_DEPTH)
+ENDIF(OSG_MULTISAMPLE_FBO_RESOLVE_IGNORES_DEPTH)
+
+
 SET(LIB_NAME osgUtil)
 SET(HEADER_PATH ${OpenSceneGraph_SOURCE_DIR}/include/${LIB_NAME})
 SET(LIB_PUBLIC_HEADERS
diff --git a/src/osgUtil/RenderStage.cpp b/src/osgUtil/RenderStage.cpp
index 54ea8aabd..737106fad 100644
--- a/src/osgUtil/RenderStage.cpp
+++ b/src/osgUtil/RenderStage.cpp
@@ -879,7 +879,14 @@ void RenderStage::drawInner(osg::RenderInfo& renderInfo,RenderLeaf*& previous, b
             switch (it->first)
             {
             case Camera::DEPTH_BUFFER:
+#ifndef OSG_MULTISAMPLE_FBO_RESOLVE_IGNORES_DEPTH
+                // This #define is a workaround for an OS X NVIDIA driver bug
+                // confirmed on GeForce 8800 with driver v1.5.49.
+                // If the glBlitFramebuffer mask includes depth, the OS X desktop
+                // will hang. The #define is controlled from CMake and should be
+                // set to ON to enable the workaround and avoid blitting depth.
                 blitMask |= GL_DEPTH_BUFFER_BIT;
+#endif
                 break;
             case Camera::STENCIL_BUFFER:
                 blitMask |= GL_STENCIL_BUFFER_BIT;