Search found 15 matches

by pinballwizard
Mon May 04, 2009 2:18 pm
Forum: General Bullet Physics Support and Feedback
Topic: Bullet SWIG (Simplified Wrapper Interface Generator) 4 Lua
Replies: 3
Views: 5194

Re: Bullet SWIG (Simplified Wrapper Interface Generator) 4 Lua

Yes, I for one would be very much interested in Python bindings. Please keep us posted on the progress!
by pinballwizard
Fri Sep 28, 2007 3:52 am
Forum: Non-technical forum and license/patent discussion
Topic: Position Based Dynamics: Patent
Replies: 56
Views: 50204

Re: Position Based Dynamics: Patent

Glad to see this discussion happening. I'm generally against software patents but recognize the reality of their existence. That said, I'm all for healthy discussion and debate about the issue, with no personal offense intended to anyone. So, here are some more thoughts... Alec wrote: As to owning a...
by pinballwizard
Thu Sep 27, 2007 4:56 am
Forum: Non-technical forum and license/patent discussion
Topic: FastLSM soft body physics (source code available)
Replies: 14
Views: 15522

Re: FastLSM soft body physics (source code available)

I think we should keep the topic about either the paper/algorithm/code or why we cannot look at the paper/algorithm/code. You're right. Sorry for derailing this particular thread. I'll bow out of this discussion for now, for the reasons of commercial/legal-risk already mentioned. To the OP: Good lu...
by pinballwizard
Thu Sep 27, 2007 2:54 am
Forum: Non-technical forum and license/patent discussion
Topic: FastLSM soft body physics (source code available)
Replies: 14
Views: 15522

Re: FastLSM soft body physics (source code available)

Unfortunately most institutional research these days seems to be going the patent route, as in some cases the metric "number of patents awarded" is used as a measure of employee performance, with minimum yearly patent quotas being imposed on individual researchers and corresponding punitive measures...
by pinballwizard
Mon Jul 30, 2007 6:27 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Jakobsen particles+Verlet -> breakable joints?
Replies: 13
Views: 8024

Another example that would be interesting would be a stack of boxes (pushing forces instead of pulling forces in a rope). Upon further reflection I realized that Jakobsen's paper suggests, due to the expense of collision detection, that collision detection and resolution only be run once per frame ...
by pinballwizard
Mon Jul 30, 2007 2:03 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Jakobsen particles+Verlet -> breakable joints?
Replies: 13
Views: 8024

Unfortunately I couldn't get the demo at http://www.gamefight.org/tensionTest/ to run on my Linux computer ("Error: Start failed: class not found: rgb2"). One question, though about your demo: did you try making the particles different masses? As I said, particles with different masses and large mas...
by pinballwizard
Mon Jul 09, 2007 12:35 am
Forum: Non-technical forum and license/patent discussion
Topic: Position Based Dynamics: Patent
Replies: 56
Views: 50204

No, but in my experience Jacobsen's scheme isn't so efficient for rigid bodies anyway. It is certainly useful for simple cloth models and often for ragdolls, but due to the extreme damping, this is really where the usefulness ends. While I'm aware of Barth and Leimkuhler's earlier work on particula...
by pinballwizard
Wed Jul 04, 2007 4:39 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Jakobsen particles+Verlet -> breakable joints?
Replies: 13
Views: 8024

This is only true if you iterate a single time; if you use several constraint iterations, the "forces" should propagate through the chain in a single frame.. the amount that they actually do propagate is dependent on the number of iterations and the order in which constraints are applied though. OK...
by pinballwizard
Sat Jun 30, 2007 5:07 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Jakobsen particles+Verlet -> breakable joints?
Replies: 13
Views: 8024

Very interesting post, ewjordan... Hence the error in the pre-corrected values will be identical, and the error doesn't function as a reasonable proxy for joint tension. The real problem is that forces are transmitted through chains of connected particles in this type of simulation over time Right. ...
by pinballwizard
Thu Jun 21, 2007 12:46 pm
Forum: Non-technical forum and license/patent discussion
Topic: Position Based Dynamics: Patent
Replies: 56
Views: 50204

Well, I think Jacobsen's way of presenting "his" method is sound since he doesn't quite claim alot of credit for it. "His" method is very well known as the lowest order approximation to a set of methods used in molecular dynamics (for rigid body molecules) since the early 80's (and those papers als...
by pinballwizard
Thu Jun 21, 2007 1:14 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Jakobsen particles+Verlet -> breakable joints?
Replies: 13
Views: 8024

Raigan, right, your suggestion also occurred to me last night and sounds reasonable. Basically every time you are "fixing up" a constraint, you are "effectively" applying a force/impulse, so by keeping a vector sum of these position correction vectors, you are effectively keeping a vector sum of the...
by pinballwizard
Wed Jun 20, 2007 5:01 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Jakobsen particles+Verlet -> breakable joints?
Replies: 13
Views: 8024

I think Barenbrug is explicitly solving for constraint forces, so he doesn't have a closed-form equation for the constraint force, but instead has to plug in the derivative/gradient/Jacobian/whatever-you-call-it :oops: of the constraint force into his quasi-Newton solver, and gets the constraint for...
by pinballwizard
Tue Jun 19, 2007 6:09 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Jakobsen particles+Verlet -> breakable joints?
Replies: 13
Views: 8024

Jakobsen particles+Verlet -> breakable joints?

Hi all, Recently I dusted off my 3D Jakobsen particle-based simulation code, implemented basically as Jakobsen described (embedded tetrahedrons in 3d collision geometry, barycentric coordinate/projection for collision resolution). I recently started implementing joints. To start off, I implemented a...