Search found 14 matches

by peterk
Wed Dec 07, 2011 5:38 pm
Forum: General Bullet Physics Support and Feedback
Topic: btGeneric6DofConstraint Angular Motors/Friction
Replies: 2
Views: 3029

Re: btGeneric6DofConstraint Angular Motors/Friction

Ok, I've finally tracked this down to the fact that ODEs quickstep (optionally) randomly reorders non-contact constraints while Bullet's sequential impulse (optionally) randomly reorders non -contact constraints. Extending the bullet random constraint reordering code to handle non contact constraint...
by peterk
Tue Dec 06, 2011 1:23 am
Forum: General Bullet Physics Support and Feedback
Topic: btGeneric6DofConstraint Angular Motors/Friction
Replies: 2
Views: 3029

Re: btGeneric6DofConstraint Angular Motors/Friction

I've attached a hacked version of ConstraintDemo.cpp which exhibits the problem. Just fire a few cubes at the centre of the constraint array with the '.' key.
by peterk
Mon Dec 05, 2011 12:54 pm
Forum: General Bullet Physics Support and Feedback
Topic: btGeneric6DofConstraint Angular Motors/Friction
Replies: 2
Views: 3029

btGeneric6DofConstraint Angular Motors/Friction

Hi, I'm attempting to use the btGeneric6DofConstraint to simulate a ball/point2point constraint with friction by enabling the angular motors with a target velocity of zero. The problem comes when trying to simulate a 2D grid of constrained bodies: B-B-B-B | | | | B-B-B-B | | | | B-B-B-B | | | | B-B-...
by peterk
Fri Nov 11, 2011 2:21 pm
Forum: General Bullet Physics Support and Feedback
Topic: Nasty bug in resolveSplitPenetrationSIMD
Replies: 6
Views: 2107

Re: Nasty bug in resolveSplitPenetrationSIMD

Just to add another data point, on Linux/gcc I'm seeing a decent performance boost when enabling SIMD on contact heavy sims. Also, I've achieved another decent improvement by replacing the _vmathVfDot3 method with the SSE4 _mm_dp_ps and also replacing the following construct _mm_or_ps( _mm_and_ps( m...
by peterk
Fri Nov 11, 2011 11:50 am
Forum: General Bullet Physics Support and Feedback
Topic: Bullet and Namespaces
Replies: 2
Views: 1448

Re: Bullet and Namespaces

Hi Erwin,

thanks for the response. I investigated this further and it looks like the gcc option -fvisibility=hidden will do what I need. If I have further problems I'll definitely look into providing a patch.

Cheers,
Pete
by peterk
Sat Nov 05, 2011 10:21 pm
Forum: General Bullet Physics Support and Feedback
Topic: Bullet and Namespaces
Replies: 2
Views: 1448

Bullet and Namespaces

Hi Erwin, I know in the past the use of namespaces has been rejected as adding unnecessary complications for library users but I'd like to explain a use case where this is proving a problem. One of the advantages of using Bullet is being able to modify the library itself to support specific requirem...
by peterk
Fri Feb 18, 2011 3:03 pm
Forum: Physics authoring tools, serialization, standards and related topics
Topic: Fracture Bodies
Replies: 1
Views: 2625

Re: Fracture Bodies

This isn't included as part of the API, but an example implementation by Erwin is available here:

http://code.google.com/p/bullet/issues/detail?id=90
by peterk
Tue Nov 16, 2010 12:47 pm
Forum: General Bullet Physics Support and Feedback
Topic: Sticking contacts with btConvexHullShape
Replies: 2
Views: 1165

Re: Sticking contacts with btConvexHullShape

No, I'm using QuickStep in ODE.

Unfortunately my scene doesn't seem to work with dynamica (or the Serialize Demo), looks like the inertia tensor is being calculated wrong. I'll try debugging this when I get some spare time and get back to you.
by peterk
Mon Nov 15, 2010 10:06 pm
Forum: General Bullet Physics Support and Feedback
Topic: Sticking contacts with btConvexHullShape
Replies: 2
Views: 1165

Sticking contacts with btConvexHullShape

Hi, I'm using a voronoi cell based shatter tool to create a large amount (1000) of stacked convex shapes with btConvexHullShape as the collision geometry. I'm finding that while fairly stable for stacking, the resulting bodies have a tendency to stick together. Only a large direct collision impulse ...
by peterk
Sat Sep 25, 2010 10:58 am
Forum: Release Announcements
Topic: Bullet 2.77 is released! OpenCL & DX11 cloth, 3ds Max plugin
Replies: 8
Views: 65524

Re: Bullet 2.77 is released! OpenCL & DX11 cloth, 3ds Max pl

The OpenCL cloth demo doesn't work for me on a Mac (Nvidia 330M), the flags are displayed but nothing happens. The MiniCL version works fine.

Particles Demo seems to work ok though.
by peterk
Thu Jan 08, 2009 3:49 pm
Forum: General Bullet Physics Support and Feedback
Topic: Occasional missed collisions in GJK (fixed)
Replies: 2
Views: 1690

Re: Occasional missed collisions in GJK

That patch seems to have completely fixed the problem for me Erwin, many thanks! Incidentally, I am setting the margin to 0 as well although this doesn't seem to cause an obvious problem in my tests. What sort of issues would I experience with GJK if I have a zero margin? What is the significance of...
by peterk
Wed Jan 07, 2009 5:39 pm
Forum: General Bullet Physics Support and Feedback
Topic: Occasional missed collisions in GJK (fixed)
Replies: 2
Views: 1690

Occasional missed collisions in GJK (fixed)

Hi, I'm using the GJK routine from Bullet to generate collisions between convex hulls. For my simulation, it's crucial for stability that even single collision events aren't missed. However what I'm seeing is that very occasionally, obviously penetrating shapes return no collision results. My questi...
by peterk
Mon Jan 05, 2009 6:55 pm
Forum: General Bullet Physics Support and Feedback
Topic: Use only narrow phase collision detection
Replies: 2
Views: 1550

Re: Use only narrow phase collision detection

Thanks, I've got this working now.
by peterk
Mon Dec 15, 2008 7:03 pm
Forum: General Bullet Physics Support and Feedback
Topic: Use only narrow phase collision detection
Replies: 2
Views: 1550

Use only narrow phase collision detection

Hi, I'm interested in using the narrow phase part of Bullet's collision detection separately, but am unsure how this is done. Ideally, I'd like to create two sets of btCollisionShape (of whatever type) plus corresponding btCollisionObject and collide them, returning the list of contacts. Can this be...