Clipping (not clipping) in opengl

I am trying to turn off all clipping mechanisms in opengl. In theory this could mean that if I pass an unclippen polygon to opengl, it would crash, but that’s not the point. The point is not why am I asking this question either, I just want to know if it can be done. Can I passed polygons to opengl that I know are already clipped, and have opengl draw the triangles without performing any kind of frustrum clipping, just to draw the polygons, without even checking if the polygons are in the frustrum or not? This has nothing to do with speed, I don’t care if it is faster to have opengl do everthing for me, I just want to know if it can be done, and how to do it.

P.S. The specification says there needs to be either the opengl defined view frustrum, or at least 6 client-defined frustrum planes. I already know this, and according to that, what I am asking can not be done, but maybe there is something I don’t know???

In standard OpenGL there’s no way to do this, but the EXT_clip_volume_hint extension (see spec at provides a way to hint that clipping is not required. Because this is only a hint, the implementation is free to ignore it, but because it’s an extension, it is likely to have the expected behavior if it’s actually supported by the implementation.

Most modern hardware these days don’t do (much) geometry clipping anyway, instead using the guard band in rasterization to get the same effect. So, depending on the driver implementation, it may already be done, in some sense :slight_smile:

works better…

you have to know that this extension is not supported by Nvidia at the moment, and it should be used by ATI… i don’t know about PowerVr boards…