Hi J-S, > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:osg-users- > [EMAIL PROTECTED] On Behalf Of Jean-Sébastien Guay > Sent: Monday, February 04, 2008 12:55 PM > To: OpenSceneGraph Users > Subject: Re: [osg-users] Displaying cables > > Hello Mike, > > Thanks a lot, good questions and suggestions here. > > - any ideas on exactly where you're bottlenecked? > > > As I said, if I set nodemask to 0 on the cables the draw time goes way > down. So I'm pretty sure the bottleneck is there (in other words, it's > not how I build the geometry, because that's being done anyways; it's > not the physics either). Though more specifically than that I can't > say.
I meant GL pipeline bottleneck: increase/decrease the number of cable segments/tessellation to see if you're geometry dispatch/transform-bound; change the aspect ratio of the cable segments (some GPUs are inefficient at rasterizing long skinny triangles; you could get a speed up by adding segments!) > > - if perception of cable width is critical, how are you ensuring the > quads are orthogonal to the viewer? Billboards, adjusting the quad > verts, viewer/quad relationship is fixed, etc? > > > Sorry, I wasn't very clear. It isn't billboards, and I can see that it > sounded like that the way I described it. We're building "cylinders" > with quad strips. So we'll give a subdivision level (number of quads > for > a segment, for example 6). And then the cable is a set of segments, > each > of which consists of 6 quads in this case. Since in this case, the > cable > with the most segments has about 20 of them (120 quads), I don't quite > see why it's so slow. Of course, it might be the display list rebuild > time, but I can't switch them off for some reason... So you're drawing 6x as many quads as necessary; that's seems a good rationale to learn geometry shaders! :-) That and moving texcoord generation off the CPU and into the vertex shader. -- mew _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
