Search found 235 matches

by bone
Thu Jan 16, 2014 4:00 pm
Forum: Career Opportunities
Topic: Physics/animation engineer position @ NaturalMotion
Replies: 8
Views: 15444

Re: Physics/animation engineer position @ NaturalMotion

I would recommend using the links in the first post to contact them directly, I doubt they are monitoring this forum post.
by bone
Wed Nov 13, 2013 3:50 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: long stick behaviour in the air
Replies: 5
Views: 6212

Re: long stick behaviour in the air

http://math.ucsd.edu/~sbuss/ResearchWeb ... 11Talk.pdf

That might help if you need more accurate methods. Sam Buss has an older paper somewhere if you want more explanation.
by bone
Mon Nov 04, 2013 6:05 pm
Forum: Links, Papers, Libraries, Demos, Movies, Comparisons
Topic: rigid body Rubik's Cube short video
Replies: 2
Views: 6111

Re: rigid body Rubik's Cube short video

Heh, nice one - thumb's up!
by bone
Tue Oct 01, 2013 4:46 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Is semi-implicit Euler unconditionally stable?
Replies: 3
Views: 6504

Re: Is semi-implicit Euler unconditionally stable?

It depends on what you're simulating. For a simple mass-spring system, there is a simple formula for whether it is too stiff for semi-implicit Euler to be stable. IIRC, the oscillation frequency has to be less than half of the physics sampling frequency.
by bone
Thu Aug 15, 2013 2:38 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Tank track simulation?
Replies: 4
Views: 8575

Re: Tank track simulation?

Good point, I agree cylinders might work pretty well.
by bone
Wed Aug 14, 2013 6:37 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Tank track simulation?
Replies: 4
Views: 8575

Re: Tank track simulation?

Not to be nitpicky, but I think you want the word "stretched" not "sketched" - I'm just mentioning this because it took me a moment to figure out what you were saying. Anyway, that's a challenging problem to do well in realtime. I think you'll definitely have to customize your solution to get what y...
by bone
Fri Aug 02, 2013 1:50 pm
Forum: General Bullet Physics Support and Feedback
Topic: how to using bullet in serverEnd?
Replies: 3
Views: 2105

Re: how to using bullet in serverEnd?

Try your question in the "General Bullet Physics ..." area, you'll probably get a better response.
by bone
Tue Jul 23, 2013 7:17 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: SI & double-pendulum: motion getting damped
Replies: 10
Views: 9450

Re: SI & double-pendulum: motion getting damped

if you're changing the velocity directly with an impulse, you're changing the energy level. And if it's "stabilizing", it's going to be towards less energy. Reasonable enough and maybe this is what happens in practice with SI but the underlying theoretical principle (if I understand it correctly) s...
by bone
Tue Jul 16, 2013 8:30 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: SI & double-pendulum: motion getting damped
Replies: 10
Views: 9450

Re: SI & double-pendulum: motion getting damped

BTW, I'm not presuming to be sure that's the *only* cause of damping. I'm just not currently aware of anything else that necessarily causes it. For example, SI may also be inadvertently causing it, simply by converging from one side of the "correct" solution.
by bone
Tue Jul 16, 2013 6:02 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: SI & double-pendulum: motion getting damped
Replies: 10
Views: 9450

Re: SI & double-pendulum: motion getting damped

Good point: my implementation of Baumgarte *is* in a system using force-level acceleration, so the damping is indeed more obvious. I'm not sure it matters that much: if you're changing the velocity directly with an impulse, you're changing the energy level. And if it's "stabilizing", it's going to b...
by bone
Tue Jul 16, 2013 3:04 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: SI & double-pendulum: motion getting damped
Replies: 10
Views: 9450

Re: SI & double-pendulum: motion getting damped

I think an answer to the second question may help with the first. Yes, the predicted velocities already handle external forces, but the main problem is that the direction of the constraint (the angle of the pendulum itself) is changing during the timestep, and that's not accounted for in most modern...
by bone
Mon Jul 15, 2013 2:56 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: SI & double-pendulum: motion getting damped
Replies: 10
Views: 9450

Re: SI & double-pendulum: motion getting damped

I think you'll find even a 'single' pendulum will get damped, because the constraint solver doesn't solve this exactly over the entire timestep, it only solves it exactly at the beginning of the timestep (at least with symplectic Euler integration, but IIRC there exists no integration scheme that wi...
by bone
Tue May 14, 2013 4:20 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: PGS Iteration: local vs. global
Replies: 13
Views: 8986

Re: PGS Iteration: local vs. global

I'm not sure what other people do, but I just consider a single collision as a constraint, to be solved generically along with every other constraint. I suppose that's closer to your global solution.