olegoandreev

Obligatory link to Errant Signal's discussion of photorealism in games: http://www.youtube.com/watch?v=FRTsl1jCqq8

A wild guess would be that OS X drivers contain poor shader optimizer.

Parallels probably work by decompiling DirectX shader bytecode back into GLSL, which is already optimized for OS X shader compiler, therefore there is less burden on the optimizer.

Another example of poor drivers are various GLES drivers on mobile, mostly trivial optimizations can drastically increase the performance: http://aras-p.info/blog/2010/09/29/glsl-optimizer/ and https://github.com/aras-p/glsl-optimizer

I hope you do realize that the errors are much harder to interpret for the non-native speakers? Where the native speaker understands, that the writer simply mixed up two words, the non-native speaker wastes a lot of time trying to parse the sentence without correcting the error. I've seen it happen many times with my colleagues.