Mathias's point that display lists are deprecated are probably the best reason to try to make the switch. If OSG isn't close to a major release, I suggest trying it and seeing if it causes problems.
As for big vs. small geometries, I used to see differences as well. Years ago, my rule of thumb was to make geometries with fewer than 200 vertices use display lists and bigger ones use VBOs. I just tested this again this morning on NVidia and Intel graphics and I see no difference anymore. However, I'm using a practical test scenario that runs through a scene in my game with geometries ranging in size from about 20 to 1000 vertices. I'm not doing a contrived test. My test scene is about 10% faster using all VBOs vs. all display lists. -- Terry Welsh www.reallyslick.com > > Message: 4 > Date: Thu, 24 Jan 2013 11:39:34 +0100 > From: Mathias Fr?hlich <mathias.froehl...@gmx.net> > To: OpenSceneGraph Users <osg-users@lists.openscenegraph.org> > Subject: Re: [osg-users] VBO as default > Message-ID: <2803708.in7vaaGG2y@notebook> > Content-Type: text/plain; charset="us-ascii" > > > Hi, > > On Thursday, January 24, 2013 10:27:48 Robert Osfield wrote: >> On 22 January 2013 20:15, Terry Welsh <mogu...@gmail.com> wrote: >> > I don't think this has been asked in a while. Is it time to switch >> > Drawables to use VBOs instead of Display Lists by default? I *always* >> > switch it manually, except for a couple exceptional situations. I >> > think VBOs are at least as fast as Display Lists and sometimes much >> > faster on modern hardware. Would this cause a lot of trouble? >> >> I was hoping that more of the community might chime in here... guess >> we are all sleeping of the winter holidays :-) >> >> I haven't done any recent tests with VBO's vs display lists, but in >> the last few years I've found that for scenes with large number of >> small geometries display lists tend to have an advantage, while scenes >> with a smaller number of larger geometries favour VBO's. The results >> are driver dependent, as well as how you manage the meshes - so a >> geometry with lots of small primitive sets would favour display lists >> while using a single triangle mesh optimized for cache coherency would >> favour VBO's. >> >> I think the best way forward would probably be to default to VBO or >> perhaps no VBO or display lists, and then use the Optimizer to decide >> which geometries to change how they are managed, including remeshing >> if one want to VBO's or just standard vertex arrays to cut down on the >> GL calling overhead. One might want to add some metrics into the >> decision of whether to use VBO vs display lists, perhaps even hardware >> dependent sets of metrics so we get the best performance from >> different type of hardware. > > My observation is quite similar. > >From what I know the display lists in the closed source drivers are done by > vbos. From what I read in the sources of the open source ones, this is just > the same. So, whatever you do you will end up using vbos technically. Well, > there is technically no other way to solve this with current hardware since > about everything is really communicated with the chip by buffer objects in > some > sense. That includes uniforms and what not ... > > Looking at dlist, I believe that the closed source one even optimizes triangle > strips and ploygons by using huger batched draws with primitive restart. Since > the driver knows about the chip and that it has the restart available in any > case for nvidia, it will do this optimization without asking the user. Whereas > if you do that as an application you need to ask for an extension here and > prepare for not having primitive restart this in the end. > > On some hardware/drivers vbos with osg are still slower than dlists. > > OTOH, dlists are deprecated and if we now start to require this, it's probably > a good time. This will also move the attention of some osg users to provide > faster geometries as long as we are not exactly close to the point where the > legacy contexts really vanish. So, it could be a good in the end to move to > vbos as default at some point. ... may be now. > > No particular emphasis on any argument. Just the thoughts ... > > Mathias > _______________________________________________ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
