From e7e860b742190e9d05bdd1a9846bc0d8e92c1769 Mon Sep 17 00:00:00 2001
From: Robert Osfield <robert@openscenegraph.com>
Date: Mon, 11 Apr 2011 19:11:25 +0000
Subject: [PATCH] Added support for explitly requesting DXT1a and DXT1c
 compression

---
 include/osg/Texture                        |  4 ++-
 src/osg/Texture.cpp                        | 30 ++++++++++++++++++++++
 src/osgPlugins/dds/ReaderWriterDDS.cpp     |  3 ++-
 src/osgPlugins/nvtt/NVTTImageProcessor.cpp |  6 +++++
 4 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/include/osg/Texture b/include/osg/Texture
index 82cc19758..53c8930ae 100644
--- a/include/osg/Texture
+++ b/include/osg/Texture
@@ -447,7 +447,9 @@ class OSG_EXPORT Texture : public osg::StateAttribute
             USE_S3TC_DXT3_COMPRESSION,
             USE_S3TC_DXT5_COMPRESSION,
             USE_RGTC1_COMPRESSION,
-            USE_RGTC2_COMPRESSION
+            USE_RGTC2_COMPRESSION,
+            USE_S3TC_DXT1c_COMPRESSION,
+            USE_S3TC_DXT1a_COMPRESSION
         };
 
         /** Sets the internal texture format mode. Note: If the texture format is
diff --git a/src/osg/Texture.cpp b/src/osg/Texture.cpp
index 2a06fa6e3..f1544b4e3 100644
--- a/src/osg/Texture.cpp
+++ b/src/osg/Texture.cpp
@@ -1299,6 +1299,36 @@ void Texture::computeInternalFormatWithImage(const osg::Image& image) const
             else internalFormat = image.getInternalTextureFormat();
             break;
 
+        case(USE_S3TC_DXT1c_COMPRESSION):
+            if (extensions->isTextureCompressionS3TCSupported())
+            {
+                switch(image.getPixelFormat())
+                {
+                    case(3):        
+                    case(4):        
+                    case(GL_RGB):   
+                    case(GL_RGBA):  internalFormat = GL_COMPRESSED_RGB_S3TC_DXT1_EXT; break;
+                    default:        internalFormat = image.getInternalTextureFormat(); break;
+                }
+            }
+            else internalFormat = image.getInternalTextureFormat();
+            break;
+
+        case(USE_S3TC_DXT1a_COMPRESSION):
+            if (extensions->isTextureCompressionS3TCSupported())
+            {
+                switch(image.getPixelFormat())
+                {
+                    case(3):        
+                    case(4):        
+                    case(GL_RGB):   
+                    case(GL_RGBA):  internalFormat = GL_COMPRESSED_RGBA_S3TC_DXT1_EXT; break;
+                    default:        internalFormat = image.getInternalTextureFormat(); break;
+                }
+            }
+            else internalFormat = image.getInternalTextureFormat();
+            break;
+
         case(USE_S3TC_DXT3_COMPRESSION):
             if (extensions->isTextureCompressionS3TCSupported())
             {
diff --git a/src/osgPlugins/dds/ReaderWriterDDS.cpp b/src/osgPlugins/dds/ReaderWriterDDS.cpp
index 9b3044a52..25302e6ea 100644
--- a/src/osgPlugins/dds/ReaderWriterDDS.cpp
+++ b/src/osgPlugins/dds/ReaderWriterDDS.cpp
@@ -177,7 +177,8 @@ struct DDSURFACEDESC2
 
 //
 // Structure of a DXT-1 compressed texture block
-// see http://msdn.microsoft.com/library/default.asp?url=/library/en-us/directx9_c/Opaque_and_1_Bit_Alpha_Textures.asp
+// see page "Opaque and 1-Bit Alpha Textures (Direct3D 9)" on http://msdn.microsoft.com
+// url at time of writing http://msdn.microsoft.com/en-us/library/bb147243(v=VS.85).aspx
 //
 struct DXT1TexelsBlock
 {
diff --git a/src/osgPlugins/nvtt/NVTTImageProcessor.cpp b/src/osgPlugins/nvtt/NVTTImageProcessor.cpp
index dbf06d6a3..a98127220 100644
--- a/src/osgPlugins/nvtt/NVTTImageProcessor.cpp
+++ b/src/osgPlugins/nvtt/NVTTImageProcessor.cpp
@@ -307,6 +307,12 @@ void NVTTProcessor::compress(osg::Image& image, osg::Texture::InternalFormatMode
         else
             format = nvtt::Format_DXT1;
         break;
+    case osg::Texture::USE_S3TC_DXT1c_COMPRESSION:
+        format = nvtt::Format_DXT1;
+        break;
+    case osg::Texture::USE_S3TC_DXT1a_COMPRESSION:
+        format = nvtt::Format_DXT1a;
+        break;
     case osg::Texture::USE_S3TC_DXT3_COMPRESSION:
         format = nvtt::Format_DXT3;
         break;