This is more efficient on my machine (nvidia), but only when applied to
groups of exactly 4 texels. So we switch to the more efficient
textureGather for groups of 4. Some notes:
- textureGatherOffset seems to be faster than textureGather by a
non-negligible amount, but for some reason, textureOffset is still
slower than a straight-up texture
- textureGather* requires GLSL 400; and at least on nvidia, this
requires actually allocating a GL 4.0 context.
- the code in opengl/common.c that clamped the GLSL version to 330 is
deprecated, because the old user shader style has been removed
completely in the meantime
- To combat the growing complexity of the polar sampling code, we drop
the antiringing functionality from EWA shaders completely, since it
never really worked well for EWA to begin with. (Horrific artifacting)
Niklas Haas
ad0d6caac7