First of all, let me apologize for making an inquiry about such an archaic EXT. It’s simply due to work requirements that I not ask about core stuff, no matter how badly I want to.
When up-sampling some read-buffer to a higher-resolution draw-buffer, we can specify linear interpolation to be used as an argument to glBlitFramebuffer - at least that’s my interpretation of the condition mentioned in the extension spec:
What about down-sampling? Normally we should not concern ourselves with implementation details, but out of specific requirement I’d like to get some insight into the likely scenarios here. Are fragments simply dropped? Is filtering in any way applied? What kind of filters come to mind?