On 2/10/07, Peter Amstutz <[EMAIL PROTECTED]> wrote: > On Wed, Feb 07, 2007 at 08:57:18AM +0900, chris wrote: > > > That is not to say this model cannot work as a hybrid system with > > portals at doorways, for space jumps etc. In fact, for very large > > scale solar/galaxy systems you would have to either use very high > > precision in the object system or maybe double precision with portals. > > > > but to get optimal accuracy, scalability etc throughout where the > > avatar travels then the graohics engine should be looking at a > > continous floating origin. > > Don't space-warping portals achive this effect? When you walk through > the portal (both the "rendering walk" as well as the actual avatar > moving through), the space rendering is now centered on a new coordinate > system. Provided your sectors are relatively small, this seems to be > more or less equivalent to the periodic recentering described in the
Sure it'll fix many problems - just like other segmentation approaches. It won't solve all, so it depends on what you want eventually. > Dungeon Siege paper you posted. One of the points of the Dungeon Siege > paper was also that recentering was a relatively expensive operation, so > you didn't want to do it every frame, but only when the camera crossed > certain boundaries, so it's not truely "continous" in the sense of doing > it before every frame. Besides, that's complete overkill, since the > point here is precision problems crop up at distances of 30-40km from > center (assuming 1 notron = 1m) so it takes a very very large world > before this becomes a problem (or you're doing a geospatial > simulation...) > The point of referring to DS was that their segmentation approach was expensive. All segmentation approaches have to have some mechanism to deal with the boundaries between segments. If you can create artificial portals and handle them efficiently then that's ok. But when they occur in places in free space - overheads and other problems can arise. Like what happens if you have an NPC on one hill and an avatar on the other and a segment boundary between. If they are fiiring at each other and possibly going back and forth across the invisible boundary what do you do? > Also, for Interreality, the issue is primarily one of representation, > since we use an off the shelf 3D engine (Crystal Space). So my concern > is how you're going to actually represent those huge worlds (since you > do have precision problems beyond 30-40km) as a downloaded map, once you > have that data loaded in, rendering is a separate issue. I can show that visible artefacts can occur even at one kilometer: e.g. when there are overlapping surfaces with small separation. A pretty common thing in a simulated natural environment. then the physics stuff can be shown to be unpredictable at 10m or 0m if time is not managed. > > (I haven't had a chance to read those other links you posted, so perhaps > those explain the idea in more detail). Np, those papers don't go into depth on how you might implement inside the graphics engine. I think it is ok to choose a portal based segmentation system as long as you can work out a way to move to a floating origin in the future. As long as youhave an efficient mechanism of itterating over the objects and can modify the navigation system and viewpoint system then you should be able to do it without difficulty. And LOD - the ability to tap into the LOD mechanism for objects and modify it will be valuable in future. If you can avoid the kind of problems of DS then you should be ok. When I finish my thesis (soon!), I'll be looking for a open source 3D system I can modify and experiment with, so I'll have more to say then. Atm, my experiments have been at two ends of the spectrum: at the low level with C/OpenGL and at the other end with working on scenegrah and x3d browsers from the outside. I'll be looking for a project and open source community that is happy to support an effort to create a floating origin version of their system. chris > > -- > [ Peter Amstutz ][ [EMAIL PROTECTED] ][ [EMAIL PROTECTED] ] > [Lead Programmer][Interreality Project][Virtual Reality for the Internet] > [ VOS: Next Generation Internet Communication][ http://interreality.org ] > [ http://interreality.org/~tetron ][ pgpkey: pgpkeys.mit.edu 18C21DF7 ] > > > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.4.5 (GNU/Linux) > > iD8DBQFFzJNzaeHUyhjCHfcRAmlDAKCYouXI1BsFG6TtrZWZe/+pOM+CtwCeI3Rr > mI9o1aiQyp5HRqeyCHUn0Yc= > =hPSI > -----END PGP SIGNATURE----- > > _______________________________________________ > vos-d mailing list > vos-d@interreality.org > http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d > > _______________________________________________ vos-d mailing list vos-d@interreality.org http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d
