Hi mille ok I understand better why rtt doesn't fit your use. As Robert says before you should read back the modelview accumulated by the cull pass .. so 2 solutions: -either you'll have to override traverse() method on all nodes -either you'll have setup your own CullVisitor managing your scenegraph
mille25 wrote: > Hi, > > that was my first idea as well, however, then I realized that this approach > does not work. > > The problem is that there is no way to know if a certain pixel still shows > the same fragment. For example, if the camera view angle changes by 180 > degrees in one frame, the pixel at the 0,0 texture coordinate would no longer > refer to the same fragment. Therefore, the program would compute the delta > between two unrelated fragments, yielding a wrong result. > > However, with my approach, the program would calculate the old fragment > position by using the old view matrix (pre 180 degree change) and the model > matrix (unchanged in this example), compute the distance to the camera and > compare it to the old distance, resulting in 0. > > Or another example: Imagine the camera looking at the ground (perfectly > planar surface) at a 45 degree angle and moving forward every frame. If I > only compared the pixel values of the output texture, every point on the > ground would yield a 0 delta distance, because the new fragment is just as > close to the camera as the old fragment. However, with my approach, each > fragment would show a negative delta distance, because they moved towards the > camera. > > Thank you! > > Cheers, > Philipp ------------------ Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=67930#67930 _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
