Chris -- Yes, you're right on the skydome and clearing. At my previous employer, we used to just draw a single fullscreen quad. and we used the texture matrix to stretch the cloud texture map according to "distance" and also to orient and move the texture in response to changes in the camera orientation. But the geometry was all eye coordinates.
(OK, that was a tangent...) Like you said, we didn't bother to do a clear before rendering the skydome, we just drew the quad at the far plane with depth test set to ALWAYS, and the net effect was that the rendering "cleared" both the depth and color buffers and prepared it for our app to render the rest of the scene with a nice tight far/near ratio. Paul Martz Skew Matrix Software LLC http://www.skew-matrix.com +1 303 859 9466 -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Chris 'Xenon' Hanson Sent: Tuesday, April 21, 2009 1:43 PM To: OpenSceneGraph Users Subject: Re: [osg-users] Geometry considered in near+far planeauto computation Paul Martz wrote: > Seems like you could do something similar with your skydome. Use a > camera to render the skydome, then a second camera to render > everything else in your scene. Maybe I'm missing something, but usually a skydome doesn't need z-buffering at all. Backface culling is sufficient for when you're inside a tessellated sphere, so you can just clear the z-buffer, turn off Z writes/compares, render the skydome, turn on z-write/compare and render the actual scene. Am I overlooking something? This has always worked for me. Concerning the huge-world-with-near-objects z-fighting problem, yeah, I've always fought with that issue. I've thought about looking at some way to mess with the z-write in a fragment shader so that it scales the z-distance according to some rule other than the (exponential?) one it uses now. That way you could have very near clip planes without wasting all of your z precision up front. But I've never tried implementing it, and I don't know if the programmable pipeline would let me get away with it. > Paul Martz > Skew Matrix Software LLC > http://www.skew-matrix.com > +1 303 859 9466 -- Chris 'Xenon' Hanson, omo sanza lettere Xenon AlphaPixel.com PixelSense Landsat processing now available! http://www.alphapixel.com/demos/ "There is no Truth. There is only Perception. To Perceive is to Exist." - Xen _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
