game-development

doom3 physics stuff

from the articulated physics editor it looks like doom3 has the following primitives:

bone -- two pyramids, base to base
box
cone
cylinder
dodecahedron
octohedron

the cone and cylinder are faceted, so my guess is there really is just one supported primitive, the convex polyhedron.

and the following constraints:

ball and socket
fixed
hinge
slider
spring

hopefully they will add a joint useful for wheels with steering and suspension, either a real one or a raycast one. otherwise i don't see too many people making mods with vehicles. maybe they have one, it just does not show up in the editor

i also played around with the test_boxstack. the physics is interesting. it has incredibly aggressive sleeping, more than even tokamak it seems. you can walk into the big tower and push out all the blocks up to your player height. as long as the pushed out boxes touch the upper boxes, the stack will stand. totally unplausible, but it still stands, no jitter or anything. which is wierd. it is as if the contacts of the lower box have no effect on the upper boxes. my stuff has used contact level sleeping forever, but damn, the doom stuff is crazy. my guess is that bodies can individually be tagged for their contact sleeping tolerance. so when the player touches something, the impulses will be propagated easily. however, any random box interacting with any random box would have a very high tolerance. the tolerance may even be anisotropic so tangent impulses effect it more than normal impulses.

i should write some scripts and build some of my own test scenes and see how well it handles things. i wonder how well it handles large mass ratios? what i really should do is write a simple mouse based manipulator so i can do proper testing, i think the scripting is powerful enough to do that sort of thing.. good job jim.