Hi J-S Some thoughts...
- any ideas on exactly where you're bottlenecked? - 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? - quadstrips are converted to tristrips in the driver; perhaps there's advantage in dispatching tristrips directly. - Ideally, and your target hardware supports it, suggest dispatch linestrip and tessellate each linesegment into a pair of tris in a geometry shader. A vertex shader could take care of texcoord computation given cable/segment lengths. Cheers -- mew > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:osg-users- > [EMAIL PROTECTED] On Behalf Of Jean-Sébastien Guay > Sent: Monday, February 04, 2008 9:43 AM > To: OpenSceneGraph Users > Subject: [osg-users] Displaying cables > > Hello, > > I imagine this is pretty common, I'm just looking for a few hints of > how > to optimize things. > > Our apps need to display cables (and most of the time, a large number > of > them). The cables themselves are controlled by a physical simulation > which gives us a set of transforms for the ends of each segment of a > cable. > > For now, we are creating some geometry (quad strips, specifically) to > display the cables, and assigning texture coordinates to that geometry, > on the fly. This is needed because if, for example, a cable is > lengthened (because it's being spooled out of a pulley system for > example) the texture shouldn't stretch over it. Similarly, if the > physical simulation subdivides the cable into more segments than it was > in the last frame, we need to have correct texture coordinates to > (hopefully) make the fact that the cable now has more, shorter segments > invisible to the user. > > I know the cable display needs to be optimized because if I just set > the > cables' nodemasks to 0, the draw times go from 6.6ms to 2.2ms (for the > same view). And there are not *that* many cables... There's a lot of > other geometry in the scene which is still drawn in the 2.2ms time... > > So I would appreciate some pointers. I would have assumed quad strips > are pretty fast, so perhaps something else is the problem? > > There's the fact that the geometry is dynamic, which could mean that > OSG > is trying to recreate display lists each frame, but I tried > setUseDisplayList(false) on the geometry and the cables just did not > display anymore... Is there something else I need to do in that case? > > Thanks in advance, > > J-S _______________________________________________ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
