Search found 85 matches

by DannyChapman
Wed Dec 23, 2015 10:09 am
Forum: General Bullet Physics Support and Feedback
Topic: Modelling a gyroscope in Bullet
Replies: 7
Views: 4196

Re: Modelling a gyroscope in Bullet

I don't have the SDK here to check the details, but don't use BT_ENABLE_GYROSCOPIC_FORCE_EXPLICIT as this will require a very small timestep to be accurate - use one of the implicit options.
by DannyChapman
Thu Dec 10, 2015 6:04 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Collision response - solver, penetration recovery
Replies: 21
Views: 8228

Re: Collision response - solver, penetration recovery

For error correction, look up "split impulses". This allows overlap to be corrected without adding momentum to the system (i.e. a sphere that starts slightly below the floor will pop up to the level of the floor in one update, but it won't do so in a way that makes it continue to move upwards in sub...
by DannyChapman
Tue May 05, 2015 1:44 pm
Forum: Release Announcements
Topic: Bullet 2.83 released on github: Example Browser, URDF
Replies: 8
Views: 55648

Re: Bullet 2.83 released on github

The feature to include the gyro terms in the solver is excellent - it turns out to be really important for correct simulation of aircraft spins and snap rolls etc, so much appreciated. I'll post a video of it in my R/C flight sim shortly.

Thanks - Danny
by DannyChapman
Wed Feb 11, 2015 10:29 am
Forum: General Bullet Physics Support and Feedback
Topic: Scientific and Technical Academy Award for Bullet Physics!
Replies: 8
Views: 3108

Re: Scientific and Technical Academy Award for Bullet Physic

Congratulations, and thanks from me for Bullet and all your efforts with it.
by DannyChapman
Tue Sep 30, 2014 3:29 pm
Forum: General Bullet Physics Support and Feedback
Topic: sailplane RigidBody wheel - constraint setup
Replies: 10
Views: 5081

Re: sailplane RigidBody wheel - constraint setup

In summary: It seems, constraints can't transfer forces between bodies, this is task for user, right? It sounds to me like a bug in the constraint, or in the way that constraints are solved. If you have two bodies that are connected together by a hard constraint (you say linear limit is zero), then...
by DannyChapman
Fri Sep 26, 2014 2:00 pm
Forum: General Bullet Physics Support and Feedback
Topic: sailplane RigidBody wheel - constraint setup
Replies: 10
Views: 5081

Re: sailplane RigidBody wheel - constraint setup

DannyChapman: However...do You think, Bullet doesn't affect constraints by external forces? Is it possible? I would make a test (e.g. hijack one of the bullet samples): Create two dynamic boxes (A and B), unit mass, zero damping, zero gravity, no static geometry. Make them not collide. Attach them ...
by DannyChapman
Fri Sep 26, 2014 9:27 am
Forum: General Bullet Physics Support and Feedback
Topic: sailplane RigidBody wheel - constraint setup
Replies: 10
Views: 5081

Re: sailplane RigidBody wheel - constraint setup

I wonder if the wheel and airframe have got different values for m_linearDamping (in the rigid body construction). If so then this would drive them apart. However, I suspect this isn't it, looking at the video again, and how the displacement happens - the wheel isn't lagging behind the airframe due ...
by DannyChapman
Tue Jun 17, 2014 10:32 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Constraint of multiple objects?
Replies: 4
Views: 6478

Re: Constraint of multiple objects?

The 6DOF joint in PhysX is asymmetric (I find this bizarre) - it will generally be more effective if the first actor in the pair is the heavier one. This might be true of the distance constraint too. One problem that you may have is that the constraints are generating more angular motion than is des...
by DannyChapman
Fri Apr 25, 2014 11:21 pm
Forum: General Bullet Physics Support and Feedback
Topic: btHeightfieldTerrainShape unusable
Replies: 2
Views: 1876

Re: btHeightfieldTerrainShape unusable

The only problems (with v2.81) I've had are: - tunnelling when the velocity is high (to be expected) - hitting internal triangle edges (not a big deal for me - and probably solvable anyway) - performance problems due to missing broad-phase tests, resulting in more low-level tests than necessary (I h...
by DannyChapman
Thu Apr 24, 2014 3:38 pm
Forum: General Bullet Physics Support and Feedback
Topic: Bumpy HeightField
Replies: 1
Views: 1600

Re: Bumpy HeightField

It will be collisions with the internal edges of the heightfield. I don't have the solution immediately to hand, but this will hopefully be enough to get you started - e.g. I'm pretty sure Erwin posted some code a while ago that flags/removes internal edges from a triangle mesh. Not sure how that wo...
by DannyChapman
Wed Mar 19, 2014 12:30 pm
Forum: General Bullet Physics Support and Feedback
Topic: Optimal way to detect collisions.
Replies: 11
Views: 5771

Re: Optimal way to detect collisions.

The heightmap because of it's regularity is pretty efficient already I'm afraid that's not quite correct. When colliding an object against the heightmap, the code does an AABB test with the heightmap's whole AABB, and then if that passes it does low level tests against all the heightmap triangles i...
by DannyChapman
Mon Mar 17, 2014 2:09 pm
Forum: Career Opportunities
Topic: Physics/animation engineer position @ NaturalMotion
Replies: 8
Views: 12823

Re: Physics/animation engineer position @ NaturalMotion

spidersharma wrote: I had applied for the given position in Jan on Natural motion web site, however there is no reply on that.
PM sent...
by DannyChapman
Wed Feb 05, 2014 12:06 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Continuous distance function
Replies: 2
Views: 2946

Re: Continuous distance function

If performance isn't a concern, you could calculate the Minkowski difference between the polyhedra and then use your generalized barycentric coordinates to get a distance measure between that and the origin which, as you say, will have a well defined derivative, and will handle overlap/separation. B...
by DannyChapman
Thu Jan 16, 2014 4:09 pm
Forum: Career Opportunities
Topic: Physics/animation engineer position @ NaturalMotion
Replies: 8
Views: 12823

Re: Physics/animation engineer position @ NaturalMotion

I would recommend using the links in the first post to contact them directly, I doubt they are monitoring this forum post. Actually I'm a regular here, but it's true you're best off contacting us through our website. For the right applicant we'd jump through whatever hoops are necessary/practical, ...