ARB_texture_compression and SGIS_generate_mipmaps

OpenGL OpenGL: Advanced Coding
1

Can I use the above mentioned extensions togehter? It looks like I can but I don’t trust it. And is it true that for using texture compression, the ONLY thing I have to do is to change the third parameter of the glTexImage2D-Command to something with “COMPRESS”, for example, GL_COMPRESS_RGBA_ARB?

Jan

2

And another point, am i assuming right that it is not wise to use texture compression for textures that are changed later with glCopyTexSubImage… because the new image first has to be compressed, eating performance?

3

I don’t know if you can use the two extensions together, but I can answer your other questions:

  1. Yes, it’s enough to use the GL_COMPRESSED_* pixel formats to enable compression.
  2. According to the spec, only the lower left corner of a compressed texture can be altered, and even then the rest of the texture is undefined. If you need compressed texture updating, you need to use specific compression formats like GL_EXT_texture_compression_s3tc.
  • elias