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Coluna
02-14-2005, 08:30 AM
Hi; In my app, the alpha channel in difuse textures is used as a mask (like fences, leaves...). When i use

glEnable(GL_ALPHA_TEST);
glAlphaFunc(GL_GREATER,0.5f);

with GLSL shaders, it didnt work, all pixels r drawned...but when i use it with nv_reg_combiners or ati_fragment_shader, it works...whats happening?

Korval
02-14-2005, 11:12 AM
Alpha testing happens after fragment processing. You should make sure that the alpha you're outputting is correct.

olmeca
06-20-2005, 11:47 AM
When I use Alpha Test + GLSL + Pbuffers on my 9600 it needs a lot of time to compute. But if I use a depth buffer with depth test, there is no such performance drop. Why does this happen?
Alpha test should be the most simplest test (no writing to a depth buffer, ... )

Zengar
06-23-2005, 06:54 AM
I think you should perform alpha test manually...

Humus
06-23-2005, 03:13 PM
Originally posted by olmeca:
When I use Alpha Test + GLSL + Pbuffers on my 9600 it needs a lot of time to compute. But if I use a depth buffer with depth test, there is no such performance drop. Why does this happen?
Alpha test should be the most simplest test (no writing to a depth buffer, ... )How much is "lot of time" in this context?

Humus
06-23-2005, 03:15 PM
Originally posted by Coluna:
Hi; In my app, the alpha channel in difuse textures is used as a mask (like fences, leaves...). When i use

glEnable(GL_ALPHA_TEST);
glAlphaFunc(GL_GREATER,0.5f);

with GLSL shaders, it didnt work, all pixels r drawned...but when i use it with nv_reg_combiners or ati_fragment_shader, it works...whats happening?Consider using alpha-to-coverage instead of alpha testing.
http://www.humus.ca/index.php?page=3D&ID=61

zed
06-23-2005, 04:27 PM
excellent as always humus (grrr now ive gotta go and play with this, as if i dont have anuf to do already)

Korval
06-23-2005, 04:39 PM
Consider using alpha-to-coverage instead of alpha testing.And what is the cost of this technique?

Humus
06-24-2005, 03:51 AM
In the demo it's about 10-15% slower than alpha testing.