----- Original Message Follows ----- From: "Robert Osfield" <[EMAIL PROTECTED]> To: [EMAIL PROTECTED], "OpenSceneGraph Users" <[email protected]> Subject: Re: [osg-users] VPB and PagedDatabase performance. Date: Wed, 27 Feb 2008 09:21:07 +0000
> On Wed, Feb 27, 2008 at 6:48 AM, [EMAIL PROTECTED] > > <[EMAIL PROTECTED]> wrote: First, thank you to everyone > > for their work putting OSG and VPB, this is really an > amazing piece of software. > > > Q1: Is there any advantage to having a single large > > osga model built from say a 16kx16k input or having > > lots of smaller 4kx4k tiled sections in separate files? > > Performance is little different. > > > Q2: Will rebuilding the database with more levels help > > smooth out lag spikes when the various LOD nodes come > > into view ? > > Do you mean more levels and small individual tiles? I built the data base as 16 tiles of 4kx4k each tile running osgdem -l 6 , would running -l 8 help performance? > What exactly do you mean by a lag spikes? A frame rate > drop, or just that it takes a long time to load the data? > > How are you storing the paged database? Locally on the > machine, over the web?? Everything is local to a single machine. I have tried release and debug versions. The machines I have been using range from an athalon x2, 2gigs of ram + built in ati video (20-30 fps) to a 2.4 gig core 2 duo , with 4 gigs ram, GeForce 8800 GTX, and 2x raid0 hard drive array. (60 fps) In both cases the lag spikes occurs at various points as the camera is moving over the database. My FPS counter might be 60,60,60,10,18,60,60,60. As soon as the data has been loaded the app runs rock steady. I have tried playing with the LoDScale settings and can minimize the impact by lowering how much of the database gets loaded. > > Q2: What are the parameters can I tweak in an OSG > > application to tweak how the program runs? > > Well there are hundreds of classes with dozens of methods > in each... so a massive set of options you can tweak. > First thing is to figure out what the actual performance > problem is then to guide in the right direction. > > > Q3: Can I force the OSG application not to swap out the > > database and just recalculate the mesh ? > > I don't understand what you mean. Is there an easy way to tell the pagedLOD's to just load the data and never retire the unused data? I think if I kept the whole thing in memory I would be golden. > > > Background: I have a 16kx16 texture and 4kx4k height > > map that I have used VPB to build a model of following > > the walk through on the wiki. While using some simple > > dynamics to fly over the terrain, my frame rates will > > nose dive at certain points when database need to be > > paged in. The terrain takes up about 500 meg on disk > > and I think might all fight in memory. > > The database should run at a solid 60Hz on most modern > PC's, you shouldn't see big nose dives in frame rate. > The database you have is pretty small, even with scaling > up to terrabytes of data you still get a solid 60Hz > without memory problems. > > What OS are you working on? What hardware? Have you > built the OSG in release mode? > > Robert. _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
