Created attachment 109319 [details]
No visual corruption on Intel (Sandybridge)

Just FYI: I had the chance to test the game on an Intel Sandybridge system and
there's no visible visual corruption in the same scene (even if it's not the
same frame). So the shader is probably ok?

The Mesa version running on that system, is a bit older though: 10.4-devel,
commit 5ccdc23a86 (and a build from 2014-09-28).