Am 09.02.2007 um 23:30 schrieb Peter Amstutz: > [...] >> Regarding physics simulation, which (if I understand you correctly) >> suffers the most from matrix creep, well... I am no expert, but >> couldn't you calculate this in a virtual coordinate space, derived >> from the world coordinates in such a fashion that all objects >> involved are close to the center? And then, once you reach some >> "stable" result, convert the virtual coordinates back to world >> coordinate space and continue from there? That may not be >> particularly precise or realistic, but again, as long as the system >> behaves more or less consistently, I can live with it. > > Hmm. Yes, you probably could do something like that, if you can > divide > up your interacting objects into isolated groups. Then you could > simulate those objects independently at the origin, then transform > them > back to the original position. Seems like a hassle, though. > Seems like this requires a coarse estimate (based on bounding boxes or so) of where physically interesting things are likely to happen. Then you could estimate a "physics combat zone" that encompasses all objects likely to be affected, and perform the calculations relative in there. If a passing object comes into the reach of the zone, you expand the zone to add the object, when you are sure it has left "physics combat" for good you shrink the zone to remove it. Well, if you want precision you've got to accept some amount of hassle, right? This is just some random idea though, I've never really worked with physics engines. Laugh away ye experts :-)
> In practice, precise consistancy is the *least* of people's worries > when > setting up a rigid body physics simulation; setting up the system > takes > a lot of tweaking just to prevent it from flipping out. > I can imagine that, considering the imprecision of floating point maths... never trust a double... > Here's a harder question: how do you handle the physics for an object > that's passing through or straddling a portal? > Again, I cannot answer that as a physics sim expert. From my environment integration POV, there is only one answer: Each environment handles its own physics simulation, including the local "half-portal". When the object passes through, you *must* let the other environment take over. Consider the case where a falling box on a space station passes through the force field of the hangar. Inside, you got friction and (artificial) gravity to consider, outside in space all this is negligible. Worse, if the space environment lives on another system, it may not even understand the physics parameters you pass. You cannot expect everybody else to know that "sim=23" in your system means "solid, slightly squishy" or that "a=42" means "crazy spin around X-axis when struck". Regards, Karsten Otto _______________________________________________ vos-d mailing list vos-d@interreality.org http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d
