I am having trouble getting automatic mipmap generation working when using glTexSubImage2D; I initially get nice mipmaps when allocting but when I replace data with glTexSubImage2D the levels from 1 to N are lost. The SGI extension spec looks ancient so I was hoping someone here has experience with automatic mipmap geneation when data is re-downloaded multiple times?

I am using the lastest NVIDIA driver (178.24) on Vista 64 bit - I am able to test this on a Linux distribution later this week; but I am kind of also asking since the *spec* at least the SGI extension is very unclear on what exactly will trigger mipmap generation if new data is downloaded (doesnt even mention downloading new data, just something about touching *edge pixels*)


The OpenGL 3.0 Specification refers to the SGI extension on page 431 but again doesnt clarify which API calls should be made for the mipmaps to be generated.