Hi Oliver, On 18/01/11 20:23 , Oliver Neumann wrote: > I need the information on vertix level, not bounding volumn level. How does > the Render > Engine know which vertices to draw. Is it all done in GPU using the Z Buffer > (overwriting what is nearer)?
OSG does not check each vertex for visibility, that would be way too expensive. Instead it's checking the Drawable against the view frustum for potential visibility. OpenGL then does finer-grained checking of the vertices against the view frustum, discarding vertices outside. Finally the Z-buffer determines if the pixels are occluded or not. But there's no way to easily get to the information which vertices actually get drawn. > OcclusionQueryNode but I cannot find any occlusion information in it. How do > I get the > visibility information stuff here? You don't, at least not on a per-vertex level. If I remember correctly OC could tell you how many pixels are visible, but not which ones. If you really need that information you have to check each pixel individually yourself. This can be made a lot faster by properly balancing the scenegraph, ie rather than putting all points into one Drawable you'd oct-tree them so that they can be more easily discarded based on the bsphere/bbox of the drawable. Again, what do you want to achieve? There might be easier ways to do that. /ulrich _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
