Search found 29 matches

by Laurent Coulon
Wed Oct 03, 2012 6:23 pm
Forum: General Bullet Physics Support and Feedback
Topic: Upcoming Bullet 2.81 release, please test trunk version
Replies: 7
Views: 6203

Re: Upcoming Bullet 2.81 release, please test trunk version

Found the problem. It is one of those annoying situations where floating point math simply fails in release builds. Essentially the situation was that sphereRelPos.y == closestPoint.y in btSphereBoxCollisionAlgorythm line 122 but sphereRelPos.y - closestPoint.y is not zero, just some small float err...
by Laurent Coulon
Thu Jul 12, 2012 10:31 pm
Forum: General Bullet Physics Support and Feedback
Topic: Major contact stability improvement
Replies: 57
Views: 31225

Re: Major contact stability improvement

Glad to hear this fixes your problem, I will post the new patch. As far as stacking stability is concerned, as I explained in my recent post what we posted in the patch is a simplified version of our solution that also works with non split impulse. Our full solution was tested at length and lead to ...
by Laurent Coulon
Thu Jul 12, 2012 7:26 pm
Forum: General Bullet Physics Support and Feedback
Topic: Major contact stability improvement
Replies: 57
Views: 31225

Re: Major contact stability improvement

Hi, Not calling integrate transforms after the solve is intentional. Objects are moved in predictUnconstraintMotion and if you are doing split impulse, they are moved again in internalWritebackVelocity. The patch does currently break CCD but if you are using CCD nothing the patch attempts to fix sho...
by Laurent Coulon
Thu Jul 12, 2012 5:00 pm
Forum: General Bullet Physics Support and Feedback
Topic: Major contact stability improvement
Replies: 57
Views: 31225

Re: Major contact stability improvement

Playing a bit with the demos in the unpatched 2.80 version shows a bug similar to what you are describing. If you run the convex decomposition demo, try grabbing one of the tables off-center and lifting it. One out of every two clicks the table will rotate properly as if it was held by a point const...
by Laurent Coulon
Wed Jul 11, 2012 10:54 pm
Forum: General Bullet Physics Support and Feedback
Topic: Major contact stability improvement
Replies: 57
Views: 31225

Re: Major contact stability improvement

Those are definitely not expected behaviors. We see no such issues in our engine, but then again we still use Bullet 2.76. The two issues you describe are identical. it looks like you have no rotations allowed on your objects. An infinite inertia tensor would yield this type of behavior. However sin...
by Laurent Coulon
Wed Jul 11, 2012 8:18 pm
Forum: General Bullet Physics Support and Feedback
Topic: Major contact stability improvement
Replies: 57
Views: 31225

Re: Major contact stability improvement

Hi Erwin, I have posted a patch for the stability improvements described earlier in the thread. https://code.google.com/p/bullet/issues/detail?id=642&colspec=Modified%20ID%20Type%20Stars%20Status%20Owner%20Summary I also provided a new BasicDemo.cpp file that highlights the improvements. We spent so...
by Laurent Coulon
Thu Jul 05, 2012 4:45 pm
Forum: General Bullet Physics Support and Feedback
Topic: Major contact stability improvement
Replies: 57
Views: 31225

Re: Major contact stability improvement

Thanks Erwin, will do. I'll post again here when I have it done.
by Laurent Coulon
Mon Jun 04, 2012 7:58 pm
Forum: General Bullet Physics Support and Feedback
Topic: Major contact stability improvement
Replies: 57
Views: 31225

Re: Major contact stability improvement

Hi Erwin,
I have grabbed the latest Bullet build. I can integrate my changes into it. Let me know how I should do this. Is there a specific repository I should use on Github? Or can I create my own svn branch on Google code?
Thanks for letting me know how to proceed.
by Laurent Coulon
Tue May 29, 2012 6:10 pm
Forum: General Bullet Physics Support and Feedback
Topic: Major contact stability improvement
Replies: 57
Views: 31225

Re: Major contact stability improvement

Hi Erwin,
Thanks for the reply. I will try to make a patch for the latest bullet version. Let me know what the name of the repository is on github. Otherwise I can post it on Google code. Let me know.
by Laurent Coulon
Fri May 25, 2012 11:45 pm
Forum: General Bullet Physics Support and Feedback
Topic: Major contact stability improvement
Replies: 57
Views: 31225

Re: Major contact stability improvement

Thanks,
I didn't know what the proper process was to do this. I will definitely try doing this.
by Laurent Coulon
Thu May 24, 2012 7:10 pm
Forum: General Bullet Physics Support and Feedback
Topic: Stability issue with btBvhTriangleMeshShape
Replies: 6
Views: 5194

Re: Stability issue with btBvhTriangleMeshShape

there seem to be a bunch of *Algorithm.cpp files that would need to change. Correct, that is what we did. It's not that many places to change overall. why would it try to merge a new contact point with an existing one if it is close enough Consider a sphere sitting on a plane. Would you really want...
by Laurent Coulon
Thu May 24, 2012 5:37 pm
Forum: General Bullet Physics Support and Feedback
Topic: Major contact stability improvement
Replies: 57
Views: 31225

Re: Major contact stability improvement

Sorry about that I should have been more explicit: We have many more changes in our Bullet code than the ones discussed in this thread. I would have to post our entire Bullet folder to let people compile it directly. The files I posted are more meant to be diffed against what you have so you can int...
by Laurent Coulon
Thu May 24, 2012 5:03 pm
Forum: General Bullet Physics Support and Feedback
Topic: Stability issue with btBvhTriangleMeshShape
Replies: 6
Views: 5194

Re: Stability issue with btBvhTriangleMeshShape

Hi JHoule, Here's a couple more issues we have found in the way persistent manifolds are being managed in Bullet: 1: When a new contact point is created, Bullet determines which of the 4 existing contacts to replace in order to maximize contact area. It is done through an approximation but we found ...
by Laurent Coulon
Thu May 24, 2012 4:36 pm
Forum: General Bullet Physics Support and Feedback
Topic: Major contact stability improvement
Replies: 57
Views: 31225

Re: Major contact stability improvement

And the last one.
That's all the main changes for the change. If I find an easy way to post the entire bullet folder somewhere, I'll let you know.