> > > As well as hardware state > > changes he also talks about the CPU cost of doing the > sorting being an > > issue. That was what my suggestion will help with as it > means that OSG > > has less states to sort, as all objects of the same type > will have the > > same state as opposed to having state where the uniform changes. > > Of course state sorting has some CPU cost, however except in > pathological cases this should be minimal compared to other > things your app does on the CPU. Perhaps you were heavily CPU > limited (that is, a severe imbalance between CPU power and > GPU power, in favor of the GPU).
For the delivery system I was dealing with that was the case, however on my dev systems which had modern fast CPUs I still was better off using this trick. > That shouldn't be the general case though, so you can't go > around recommending that everyone use vertex attributes > instead of uniforms in all cases - most of the time people > will want to use uniforms for things that can change per > object, and vertex attributes for things that can change per vertex. > If this isn't faster on other people's apps I'd like to know ( to improve my own knowledge if nothing else ). It was Robert who suggested that I use this technique and he said that Uniforms can be expensive and that State changes should be minimised. However using a Uniform per object is far easier, if it gives comparable performance it is certainly the better option. It's more a case of letting people know that there is a gotcha that comes with the heavy use of Uniforms and that there is a way around it using techniques in the osgexamples. Colin. _______________________________________________ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
