Prior to 8c00f6da88 the interpolation of fragment
shader inputs appears to not have been accounting for perspective. This broke
texturing due to the texture ids being interpolated for perspective which was
fixed in 47e0ac8032. The hsl values similarly
require not accounting for perspective, so the noperspective interpolation
qualifier has been added. It is unclear to me why the geometry shader removal
would affect the interpolation like this since it was emitting vertices with
the correct z values.
34c8bfb2f4