From Wojciech Lewandowski, "Here are my changes:

- osg::Texture sets GL_MAX_TEXTURE_LEVEL if image uses fewer mipmaps than
number from computeNumberOfMipmaps (and it works!)
- DDS fix to read only available mipmaps
- DDS fixes to read / save 3D textures with mipmaps ( packing == 1 is
required)
- Few cosmetic DDS modifications and comments to make code cleaner (I hope)

Added _isTextureMaxLevelSupported variable to texture extensions. It
could be removed if OSG requires OpenGL version 1.2 by default.

Added simple ComputeImageSizeInBytes function in DDSReaderWrites. In
my opinion it would be better if similar static method was defined for
Image. Then it could be used not only in DDS but other modules as well (I
noticed that Texture/Texture2D do similar computations).

Also attached is an example test.osg model with DDS without last mipmaps to
demonstrate the problem. When loaded into Viewer with current code and moved
far away, so that cube occupies 4 pixels, cube becomes red due to the issue
I described in earlier post. When you patch DDS reader writer with attched
code but no osg::Texture yet, cube becomes blank (at least on my
Windows/NVidia)  When you also merge osg::Texture patch cube will look right
and mipmaps will be correct."

src/osg/Texture.cpp

@@ -30,6 +30,11 @@ using namespace osg;
 #define GL_TEXTURE_WRAP_R                 0x8072
 #endif
 
+#ifndef GL_TEXTURE_MAX_LEVEL
+#define GL_TEXTURE_MAX_LEVEL              0x813D
+#endif
+
+
 #ifndef GL_UNPACK_CLIENT_STORAGE_APPLE
 #define GL_UNPACK_CLIENT_STORAGE_APPLE    0x85B2
 #endif
@@ -795,6 +800,15 @@ void Texture::applyTexParameters(GLenum target, State& state) const
         if(wr == CLAMP_TO_BORDER)
             wr = CLAMP;
     }
+    
+    const Image * image = getImage(0);
+    if( image &&
+        image->isMipmap() &&
+        extensions->isTextureMaxLevelSupported() &&
+        int( image->getNumMipmapLevels() ) <
+            Image::computeNumberOfMipmapLevels( image->s(), image->t(), image->r() ) )
+            glTexParameteri( target, GL_TEXTURE_MAX_LEVEL, image->getNumMipmapLevels() - 1 );    
+
 
     glTexParameteri( target, GL_TEXTURE_WRAP_S, ws );
     
@@ -802,6 +816,7 @@ void Texture::applyTexParameters(GLenum target, State& state) const
     
     if (target==GL_TEXTURE_3D) glTexParameteri( target, GL_TEXTURE_WRAP_R, wr );
 
+    
     glTexParameteri( target, GL_TEXTURE_MIN_FILTER, _min_filter);
     glTexParameteri( target, GL_TEXTURE_MAG_FILTER, _mag_filter);
 
@@ -1592,6 +1607,7 @@ Texture::Extensions::Extensions(const Extensions& rhs):
     _isNonPowerOfTwoTextureNonMipMappedSupported = rhs._isNonPowerOfTwoTextureNonMipMappedSupported;
 
     _isTextureIntegerEXTSupported = rhs._isTextureIntegerEXTSupported;
+    _isTextureMaxLevelSupported = rhs._isTextureMaxLevelSupported;
 }
 
 void Texture::Extensions::lowestCommonDenominator(const Extensions& rhs)
@@ -1624,6 +1640,7 @@ void Texture::Extensions::lowestCommonDenominator(const Extensions& rhs)
     if (!rhs._isNonPowerOfTwoTextureNonMipMappedSupported) _isNonPowerOfTwoTextureNonMipMappedSupported = false;
 
     if (!rhs._isTextureIntegerEXTSupported) _isTextureIntegerEXTSupported = false;
+    if (!rhs._isTextureMaxLevelSupported) _isTextureMaxLevelSupported = false;
 }
 
 void Texture::Extensions::setupGLExtensions(unsigned int contextID)
@@ -1713,6 +1730,8 @@ void Texture::Extensions::setupGLExtensions(unsigned int contextID)
     
     if (_glTexParameterIiv == NULL) setGLExtensionFuncPtr(_glTexParameterIiv, "glTexParameterIivEXT");
     if (_glTexParameterIuiv == NULL) setGLExtensionFuncPtr(_glTexParameterIuiv, "glTexParameterIuivEXT");
+
+    _isTextureMaxLevelSupported = ( getGLVersionNumber() >= 1.2f );
 }