On Jan 7, 2008 10:58 AM, Wojciech Lewandowski <[EMAIL PROTECTED]> wrote: > I am also very surprised to see that use of index arrays/buffer objects > impacts performance. Is this a limitation of OSG or OpenGL ? I always > thought that Hardware Vertex Buffer + Hardware Index Buffer should be the > best performing scenario.
Don't confuse vertex indices supported by osg::Geometry with that of indices support by osg::DrawElements* (wrapper of glDrawElements(..). vertex indices lead to the slow path == BAD. vertex arrays + DrawElelemtsn lead to fast path == GOOD :-) > I just checked GPU_Programming_Guide on NVidia Developer site and found > following excerpt in Chapter 3 General GPU Performance Tips: > > " > ... > 3.3 Vertex Shader > > 3.3.1 Use Indexed Primitive Calls > > Using indexed primitive calls allows the GPU to take advantage of its > post-transform-and-lighting vertex cache. If it sees a vertex it's already > transformed, it doesn't transform it a second time-it simply uses a cached > result. > ... > " > > It seems to contradict what Robert said... No contradication... re-read the various post given and look for the distinction between vertices indices and primitive indices. Robert. _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
