OpenGL Culling going crazy
Author
I've got a very strange problem with a game I'm making.
When I enable backface culling, everything starts out looking OK. But sometimes, for some reason (or for no reason! ;)), the culling is reversed. I only enable culling in one location of my program, so it's not a situation with different functions messing up the culling state variables.
Why on earth would this happen? I enable culling, set the culling to GL_BACK, set the front face to GL_CCW, and it still reverses itself and starts showing the opposite side of everything every once in a while.
If you are definately not changing the winding order yourself then the problem could lie with buggy old drivers [smile] Have you tried upgrading your graphics card drivers to the latest version?
You could also stick...
All the best,
ViLiO
You could also stick...
GLint i;glGetIntegerv(GL_CULL_FACE_MODE, &i);All the best,
ViLiO
Quote:Original post by Halma
When I enable backface culling, everything starts out looking OK. But sometimes, for some reason (or for no reason! ;)), the culling is reversed.
Some transformations will cause this, the most common one would be using a negative scale (for reflections and the like). If you're doing that you need to invert the culling for the reflection and put it back again afterwards.
Author
Thanks for the replies.
I don't think the problem is with drivers; I have an NVIDIA GeForce 6600, and my drivers are at worst, about a year old. Besides, I've seen my program do the same thing on at least one other computer.
I don't have any reflections, and I hardly have any scaling at all, so I don't think the problem is with negative scaling. In any case, I glPopMatrix after my transforms.
I'll try the breakpoint thing; I'll tell you how it goes.
I don't think the problem is with drivers; I have an NVIDIA GeForce 6600, and my drivers are at worst, about a year old. Besides, I've seen my program do the same thing on at least one other computer.
I don't have any reflections, and I hardly have any scaling at all, so I don't think the problem is with negative scaling. In any case, I glPopMatrix after my transforms.
I'll try the breakpoint thing; I'll tell you how it goes.
I guess it's due to Orthographics projection.
It once happenned with me, and I had no time to check the reason with it because I had to deliver my program before the deadline. Anyway, I have done all in reverse in order to find a short term solution, and since that time, I havn't had the chance to dedicate some time to Graphics...
Best Regards,
Ali B
It once happenned with me, and I had no time to check the reason with it because I had to deliver my program before the deadline. Anyway, I have done all in reverse in order to find a short term solution, and since that time, I havn't had the chance to dedicate some time to Graphics...
Best Regards,
Ali B
Are you by any chance using wglUseFont functions to draw text? I don't know why the hell they change the winding, but they do. I have to reset the winding to glFrontFace(GL_CCW) right after I'm done drawing text, or else the culling gets screwed up.
Author
Quote:Original post by mikeman
Are you by any chance using wglUseFont functions to draw text? I don't know why the hell they change the winding, but they do. I have to reset the winding to glFrontFace(GL_CCW) right after I'm done drawing text, or else the culling gets screwed up.
YES!! I love you!
Thanks a lot, that fixed it!
What kind of $#% programmer changes the global states without changing them back??!
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