If I have a non-compressed cubemap texture, and I want to make it a compressed cubemap texture, I suppose I have to blit it to the compressed internal format, right?
How to do that is very unclear to me based on a reading of the extension specs. EXT_framebuffer_blit contains not one reference to "cube", and EXT_framebuffer_object contains not one reference to "blit".
So how to blit a cube texture to another cube texture? Is it legal to use glFramebufferTexture2DEXT(GL_READ_FRAMEBUFFER_EXT, ...,GL_TEXTURE_CUBE_MAP_POSITIVE_X,...) to select the source to blit from, similar to how I normally use it to select the draw face with GL_FRAMEBUFFER_EXT? Or can I blit the whole cube at once by selecting GL_TEXTURE_2D instead of a cube face? Or how?
thanks in advance.