I’m working with a fragment shader that has run fine on ATI/NVidia on Windows and with NVidia on Mac OS X, but recently discovered that with ATI on Mac OS X (10.5), the gl_FrontFacing variable is always true. I have reported this to Apple, but received no comments. Has anyone else run into this?
(I have also discovered that attempting to use edge flags with glDrawArrays(GL_TRIANGLE,… ) ATI / Mac OS X is futile…)
Thanks for the advice to post on mac-openl scratt! ATI are helping me out now.
I successfully implemented a workaround with secondary back and front colors for gl_FrontFacing emulation that works great. The edgeflags thing was a confirmed bug.
No worries. For all their little niggles with drivers ATI seem far more responsive and genuinely concerned about issues than any other vendor. Glad you got some help.