On Tue, Feb 27, 2007 at 10:14:51PM +0100, Benjamin Mesing wrote: > On Tue, 2007-02-27 at 11:03 -0500, Peter Amstutz wrote: > > On Tue, Feb 27, 2007 at 09:03:44AM -0500, Reed Hedges wrote: > > > > > Each object should be internally responsible for deciding how it > > > responds to physical forces (messages requesting movement), I think. > > > force message, etc.? > > > > There's two problems with that: [..] the second is basic > > Newtonian physics, that for each action there is an opposite reaction, > > so if I push on a box, the box also "pushes back" > > I do not see the problem here. Reed was saying, that the object should > decide how it *responds* to force. If e.g. a humanoid object wants to > push a box, it sends a force message to itself and the object.
(Assuming all remote objects in these examples.) I think the basic criticism that Peter is giving is this: Imagine that box is bolted to the ground or is covered with sandpaper, friction and tensile forces etc. ought to prevent it from moving. So the box has to send updates back to the humanoid and otherobjects that indicate at what speed it's moving (or not at all). Then when that box detects a collision with some sphere, say, it has to send a message to that sphere to make it move. But maybe the box's view of the world is out-of-date vs. the client's or the sphere's view. It takes time to send those messages over the internet, which causes basically race conditions (as Pete mentioned with pushing the box off a cliff) or just ugly jittery lag. My idea above implies that the physics simulation is done as a big conversation/dialog of messages. This has no problems if we were on a superfast LAN, but we want it to work reasonably well on the internet. To do that we need to introduce extra complexity than just messages requesting that forces be applied-- it turns each movement into an N-way transaction negotiation of some kind. I think it could be done, but it may be hard to get right, and that downside may not oughtweigh whatever its benefits. It may be worth exploring a bit more though? Reed _______________________________________________ vos-d mailing list vos-d@interreality.org http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d
