In D16777#457638, @Clément Foucault (fclem) wrote:

The changes looks fine. I just have a couple of nitpicks.

However, I still wonder why the different default textures are needed. If I remember correctly, theses are only used if there is a missing texture from an Image datablock and thoses texture are always floats as far as I know.

Thanks for the review!
As discussed in the meeting, this appears to be purely an issue of satisfying Metal validation being strict about having the correct image formats/types bound to a given sampler, rather than pure correctness. Disabling validation enables the app to work correctly, but the default textures with formats were added as a catch-all to also cover future functionality.

It hadn't been added up until this point, as paths were not triggering errors. I believe the only real problematic case being triggered was for texture buffers, where it appeared some texture buffers wanted floating point format, and others integer.

Though I will confirm the case where a default texture of mis-matched format is needed (hair shaders jump to mind, before data is prepared, or for the cases where a particular set of data is not used).