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Damien Marchal
05-11-2004, 11:45 PM
Hi,

I have a (cg) fragment program execute on big polygons, to increase the performances i tried to use additional clip plane (i could do manual clipping of course).

As i get non speed change i was asking if i missed something ? Is it the expected behavior or is it just my code which is buggy ?

Cheers,
Damien,

plasmonster
05-14-2004, 11:26 PM
Damien,

it's always been my experience that user defined clip planes are just plain slow. I would avoid using them if possible in performance critical areas. There's an oblique frustum technique that might just do the trick in your case.

Here's a link to a related paper:
http://www.cs.unc.edu/~lowk/research/writings/lowk_max_image.pdf

Here's a related thread:
http://www.opengl.org/discussion_boards/cgi_directory/ultimatebb.cgi?ubb=get_topic;f=6;t=000170

Damien Marchal
05-18-2004, 12:44 AM
Hi,

thank for the links.

As i have to handle an unknow number of additional clip planes i finally decieded to do manual clipping and then draw the shape with GL_POLYGON. This gives a big performance boost.

Cheers,
Damien.