> vertex indices lead to the slow path == BAD. > > vertex arrays + DrawElelemtsn lead to fast path == GOOD :-)
Thats a relief. I was afraid I will have to fix all my code ;-) Cheers, Wojtek ----- Original Message ----- From: "Robert Osfield" <[EMAIL PROTECTED]> To: "OpenSceneGraph Users" <[email protected]> Sent: Monday, January 07, 2008 12:20 PM Subject: Re: [osg-users] VBO > 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 > _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
