This is actually a known problem according to the Terrex developers. You can see the problem sometimes by just sitting in one place and rotating the camera slightly.
We got some updated code from them as a pre-release that, according to them, fixed the problem. It didn't really fix it, and we can't give the code out. It made it a little better sometimes, but not always. They said that it was solved as far as they were concerned because it looked okay in the OSG viewer, but only because it popped back to the right LOD after a second or two. In a busy simulation, that turned into a lot longer time or not at all. Either way, we inadvertently found a work-around when we modified the cull visitor to traverse some data behind us down to the geode, but decide not to draw it at the last moment, so we could keep the geometry loaded into our physics engine. That fixed the problem, but only if we accept data a fairly large distance all around, I think about 200 meters. This negatively affects performance, for obvious reasons, which exacerbates the problem that TerraPage terrains loaded into OSG render inefficiently using thousands of draw calls for high resolution terrains. This is a lack of optimization problem with the OSG loader, and not necessarily TerraPage itself. Essentially what we do is accept nodes if they are in the view frustum, or in a certain radius of the view. We then only accept Geodes that are in the view frustum. Any Geode we find gets loaded, or updated in the physics engine, and doesn't get paged out. -----Original Message----- From: [EMAIL PROTECTED] on behalf of Robert Osfield Sent: Mon 2/18/2008 6:00 AM To: OpenSceneGraph Users Subject: Re: [osg-users] LOD problems using OSG with TerraPage Hi Kiff, I can't really provide a good answer as there is way too little info about the problem for me to get the bottom of it remotely, one really needs the database and the an animation path that reproduces the problem, then one can start digging in to it. It might be a database set up problem, it might be a bug in the OSG's TXP plugin, it might simply be an artefact of the way that the TXP plugin has to manage LOD's to ensure that no cracks between adjacent tiles appear. There is a chance that Terrax engineers have seen this problem and know of a solution. Terrex do have an update to the OSG's Terrex plugin that is awaiting completion and approval for release, but this has been the state of play for over six months I'm still awaiting source code from them... Whether this update will fix you problem or not I have no idea, but it would be worth contact them about it. Robert. On Feb 18, 2008 1:08 AM, Kiff Loh <[EMAIL PROTECTED]> wrote: > Hi, > > I'm using OSG viewer to see a txp terrain generated by Terra Vista. I > have 10m and 1m imagery, with multiple LODs. > > I noticed that when I'm doing low level flying using OSG viewer, my most > detailed LOD sometimes switches to the 2nd LOD. I'm flying just above > the terrain, so it is quite impossible that the 2nd distances switched > in. > > I've tried 3 LOD (10m) with high resolution insets (1m), 3 LOD (10m) > with 6 LOD AOI (1m), and I noticed the problem pops most of the time > when I generate the database. I've tried shifting the 2nd LOD to 50,000m > to avoid the problem, but it still appears. > > Please help. > > 777 > > > > -----Original Message----- > > > _______________________________________________ > osg-users mailing list > osg-users@lists.openscenegraph.org > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > _______________________________________________ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org _______________________________________________ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
