bgolus

> However I would suggest a different interpretation of the issue: the function to calculate the coordinates is discontinuous, and the solution to switch between 2 equivalent variants that have...

It doesn't work on Mali? Super fascinating! What do you see here: https://www.shadertoy.com/view/WdccRS Do you see "3 stipes" with the middle stripe showing diagonal lines, or 6 boxes with each...

Noooo! That means Mali defaults to coarse shader derivatives, and uses full quad derivatives for the mip level calculation! That means only the explicit LOD / gradients methods will work...