## Search found 24 matches

Wed Sep 09, 2009 5:50 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Fastest convex polyhedron collision detection algo
Replies: 2
Views: 2849
V-Cilp may be faster than GJK,but I think enhance GJK algorithm is pretty good.
Wed Oct 29, 2008 3:29 pm
Forum: General Bullet Physics Support and Feedback
Topic: ConvexHull verse btBvtTriangleMeshShape
Replies: 3
Views: 2135

### Re: ConvexHull verse btBvtTriangleMeshShape

you mean the contact points generated by the collision right? You can provide a callback that bullet will call during the processing of collision - more information here: http://www.bulletphysics.com/mediawiki-1.5.8/index.php?title=Collision_Callbacks_and_Triggers That is to say that the penetrated...
Tue Oct 28, 2008 6:03 am
Forum: General Bullet Physics Support and Feedback
Topic: ConvexHull verse btBvtTriangleMeshShape
Replies: 3
Views: 2135

### ConvexHull verse btBvtTriangleMeshShape

Hi all
How should i use bullet to return the penetration vertices after performing the ConvexHull verse btBvtTriangleMeshShape collision detection .
I will use it for view frustum occlusion and want to know which vertices in the view frustum accurately.
Thanks
-jiangwei
Sun Apr 06, 2008 8:35 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Friction and LCP
Replies: 23
Views: 6722

### Re: Friction and LCP

Hi
Do not use Lemke method to solving LCP,its slow and can not be control.
So PGS or SI (developed by Erin catto)is better choice to solving velocity-level constraints
But i think the position-level theory is the future
Mon Dec 17, 2007 7:11 am
Forum: General Bullet Physics Support and Feedback
Topic: Crash on Vector Math Library "=" operator
Replies: 9
Views: 2989

### Crash on Vector Math Library "=" operator

Hi all: I had written a console app for test SSE version Vector3,but its crash on line "m_minimum = val" in Region::setMinimum function. The Scalar version has no problem. Why? :( #include "stdafx.h" #include <vector> #include "Region.h" int _tmain(int argc, _TCHAR* argv[]) { std::vector<Region*> tm...
Wed Jun 13, 2007 2:57 am
Forum: Links, Papers, Libraries, Demos, Movies, Comparisons
Topic: Ageia paper on position based physics
Replies: 73
Views: 55907
Is there any open source physics engine which used position based method?
thanks
Fri Sep 29, 2006 6:43 am
Forum: General Bullet Physics Support and Feedback
Topic: Bullet & ODE LCP Solver
Replies: 3
Views: 3175

### Re: Bullet & ODE LCP Solver

Good point. We recently discussed this reordering of constraints. Doing a randomize can work in some situations, but opinions vary. Other approaches are sweeping back-and-forwards or sorting them in order of deepest penetration. See the discussion here: http://www.continuousphysics.com/Bullet/phpBB...
Thu Sep 28, 2006 9:48 am
Forum: General Bullet Physics Support and Feedback
Topic: Bullet & ODE LCP Solver
Replies: 3
Views: 3175

### Bullet & ODE LCP Solver

Hi All if ((iteration & 7) == 0) { for (i=1; i<m; ++i) { IndexError tmp = order[i]; int swapi = dRandInt2(i+1); order[i] = order[swapi]; order[swapi] = tmp; } } I attentioned this section code which in the "SorLcp.cpp" can improve the stable,but i don't know why. There no papers to discussed this. I...
Fri May 26, 2006 3:04 am
Forum: General Bullet Physics Support and Feedback
Topic: About correct error and stack stable
Replies: 9
Views: 7811
-I meant if you choose an arbitrary direction or align the first tangential direction with the raltive tangential velocity. This might give you better results... remiss of i not to read your post carefully,sorry for my mistake. yes,i used raltive tangential velocity direction as my first tangent di...
Tue May 23, 2006 11:39 am
Forum: General Bullet Physics Support and Feedback
Topic: About correct error and stack stable
Replies: 9
Views: 7811
Thank you for you reply ! - How many contact points do you generate? every vertex of box. - Do you use SAT or GJK with some kind of manifold like Erwin? Yes. - How do you choose the tangential direction at the contact point / manifold center? Contact point. - How many friction constraints do you def...
Tue May 23, 2006 4:36 am
Forum: General Bullet Physics Support and Feedback
Topic: About correct error and stack stable
Replies: 9
Views: 7811

### About correct error and stack stable

Hi all My physics engine used PGS to solve the LCP and use error reduction parameter ,it can run correctly when exist few boxs in physics world ,but when i build a box stack then begin to honrizontal moved and quake. the box stack that collapseed only in 2 second. My question is how to correct this ...
Mon May 22, 2006 12:41 am
Forum: General Bullet Physics Support and Feedback
Topic: Why is stacking unstable?
Replies: 6
Views: 5713
My physics engine used PGS to solve the LCP too,this undesired tangent velocity is also exist in my physics engine
i find OPENTISSUE also have this problem,but it build a first order system to correct this error.
Fri May 19, 2006 5:31 am
Forum: General Bullet Physics Support and Feedback
Topic: Why is stacking unstable?
Replies: 6
Views: 5713
You could use error reduction parameter as OPENTISSUE and ODE did, Add Kerp * 1/delta t * -penetration distance to term b,It can make your box stack stable in vertical direction.
Tue Apr 11, 2006 3:01 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Contact Manifold Generation: A question about GJK
Replies: 16
Views: 30031