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harkal
08-31-2000, 05:18 PM
I'm trying to use the alfa test to draw
a polygon with a hole in it. The hole has
an alfa value of 0 and the rest of the texture has 255. I use the GEQUAL function with a value of 128 but nothing happens...

What is the problem? Is there a special way I have to init my framebuffer to get alfa tests to work? or is it something else?

Thanks
Harry

Bob
09-01-2000, 12:54 AM
Called glEnable(GL_ALPHA_TEST)?

And if you are using glAlphaTest() you must pass the alpha reference as a float in the range [0,1].

harkal
09-01-2000, 02:50 AM
Well the problem is that I'm enabling alfa test but nothing happens(I use 0.0 -> 1.0 values also). I can't explain it. My video
card is based on nVidia's TNT2 and supports
it for sure. The problem is somewhere else http://www.opengl.org/discussion_boards/ubb/frown.gif

Bob
09-01-2000, 02:58 AM
I'm not sure if this will affect the alpha test at all, but it can be that you have to use a framebuffer that support alpha - RGBA. Maybe you are using a RGB framebuffer.