Search found 78 matches
- Fri May 24, 2013 9:16 am
- Forum: Links, Papers, Libraries, Demos, Movies, Comparisons
- Topic: Great Physics Engine Comparison (PEEL)
- Replies: 29
- Views: 179046
Re: Great Physics Engine Comparison (PEEL)
I for one is really happy that Pierre published his results, regardless of supposed biases, there was a time not so long ago where posting on the Bullet forum lead to enlightening discussions instead of flame wars. This should be a technical discussion, because the reality is, most real time physics...
- Mon Mar 30, 2009 9:13 am
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: GJK Warm Starting
- Replies: 3
- Views: 6739
Re: GJK Warm Starting
Degeneracies are still possible. Yes, right, I haven't thought about that, I'm going to check my own code :) If you store simplex vertices (position, not index) in shape local space, it should be possible to make warm-starting work for implicit primitives too, but having to apply the inverse transf...
- Fri Mar 13, 2009 6:41 am
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: GJK Warm Starting
- Replies: 3
- Views: 6739
Re: GJK Warm Starting
For polytopes, a cheap warming is to use center masses as an initial direction, that give you some speed-up, and does not require to store anything. Now if you want to cache the last simplex, you could store it as a list of vertex pairs ([vertexIndexInA,vertexIndexInB], etc...) , rebuild and solve t...
- Sat Jan 10, 2009 8:21 am
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: magnetic sim
- Replies: 5
- Views: 14879
- Thu Dec 04, 2008 12:43 pm
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: EPA Simplification - Side-stepping Robustness Issues
- Replies: 4
- Views: 12849
Re: EPA Simplification - Side-stepping Robustness Issues
Have you compared your ideas with Bullet EPA implementation ? (btGjkEpa2.cpp)
Nathanael.
Nathanael.
- Wed Oct 29, 2008 1:05 am
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: ApplyForce() adds excess energy
- Replies: 3
- Views: 4919
Re: ApplyForce() adds excess energy
Its a common observation, I think the best explanation can be found here: http://www.cs.cmu.edu/~baraff/sigcourse/notesd1.pdf page 29, section 5.5
Hope it help,
Nathanael.
Hope it help,
Nathanael.
- Sat Oct 25, 2008 3:37 am
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: Polygon soup with polygon soup collision detection
- Replies: 5
- Views: 8032
Re: Polygon soup with polygon soup collision detection
Is there any info or know techniques for convex decomposition? This is the first time i hear this term formally... The simplest way that I'm aware of is to recursively split the mesh with itself, (complete convex decomposition), then merge resulting convex sets based on some heuristic (aspect ratio...
- Fri Oct 17, 2008 3:47 am
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: Soft Body Parameterization
- Replies: 1
- Views: 4069
Re: Soft Body Parameterization
It is probably possible to apply large damping on soft bodies deformations (but not global motion), to achieve some kind of Clay like behavior, but it is currently not implemented. Clay behave very much like an highly viscous fluid, with very little elastic forces, so, my guess is smoothed particle ...
- Mon Sep 15, 2008 10:10 am
- Forum: General Bullet Physics Support and Feedback
- Topic: leaks again [solved]
- Replies: 8
- Views: 9658
Re: leaks again
Can you update your btSoftBody.h/cpp to latest svn version, and check if the leaks gone?
Thanks,
Nathanael.
Thanks,
Nathanael.
- Sat Sep 13, 2008 1:19 pm
- Forum: General Bullet Physics Support and Feedback
- Topic: friction model
- Replies: 4
- Views: 14232
Re: friction model
What you have is an infinitely rigid cylinder rolling over an infinitely rigid plane, no amount of 'classic' friction will ever stop the cylinder motion. Most real life objects deform slightly on contact, and provide some non-zero area contact surface, they lose some energy when regaining their orig...
- Sat Sep 13, 2008 10:03 am
- Forum: General Bullet Physics Support and Feedback
- Topic: friction model
- Replies: 4
- Views: 14232
Re: friction model
Part of the problem may come from the fact that when only one contact is created between your cylinder and the plane, nothing prevent/damp angular velocities about the contact normal (contacts are points, not surfaces). Try adding a bit of angular damping along that axis, that should work. Hope it h...
- Thu Sep 11, 2008 2:15 am
- Forum: Release Announcements
- Topic: Bullet 2.71 released: Disney Maya Plugin, CUDA experiments
- Replies: 10
- Views: 106598
Re: Bullet 2.71 released: Disney Maya Plugin, CUDA experiments
But why it should be 11% slower? Only one method is slower (btDbvtVolume::Select), when measured by the internal benchmark (btDbvt::benchmark). It may be due to the way the compiler allocate registers in that case (the method is inlined), but its not big deal, and does not mean its actually slower ...
- Sun Sep 07, 2008 9:30 am
- Forum: Release Announcements
- Topic: Bullet 2.71 released: Disney Maya Plugin, CUDA experiments
- Replies: 10
- Views: 106598
Re: Bullet 2.71 released: Disney Maya Plugin, CUDA experiments
Can you try the lastest svn version of btDbvt.h/cpp , SSE has being re-enabled, it use intrinsics now.DevO wrote: One question why using inline asm and not SSE intristics.
SSE intristics can be compiled on 64bit and on 32bit and GCC compilers support them too.
Thanks,
Nathanael.
- Sun Aug 31, 2008 12:44 am
- Forum: General Bullet Physics Support and Feedback
- Topic: btGjkEpaSolver2 error
- Replies: 6
- Views: 7229
Re: btGjkEpaSolver2 error
I can see two likely possibilities for your problem: 1- when GjkEpa2::Penetration is called , there's just not enough stack space free to allocation instances of epa on it, if so, you can try to allocate epa on the heap, here's a quick patch to test that: case GJK::eStatus::Inside: { EPA& epa(*(...
- Sat Aug 30, 2008 4:54 am
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: Position based dynamics collisions
- Replies: 3
- Views: 5529
Re: Position based dynamics collisions
You could try to express the position in triangle as barycentric coordinate let say: P0*u+P1*v+P2*(1-u-v)
then your triangle gradients simply become :
[ -N*u , -N*v , -N*(1-u-v) ]
(based on C=(q-(P0 u + P1 v + P2 (1-u-v))).N )
Hope its work and help,
Nathanael.
then your triangle gradients simply become :
[ -N*u , -N*v , -N*(1-u-v) ]
(based on C=(q-(P0 u + P1 v + P2 (1-u-v))).N )
Hope its work and help,
Nathanael.