Search found 814 matches

by drleviathan
Mon Oct 17, 2022 3:33 pm
Forum: General Bullet Physics Support and Feedback
Topic: [ammo] Problems with rigidity of sequential constraints
Replies: 2
Views: 370

Re: [ammo] Problems with rigidity of sequential constraints

Yes, I think you are right: large ratios between the mass/inertia of constrained objects are contributing to the error of the constraint solution. I believe the problem still reproduces in the latest version of Bullet, but I haven't tested constraints in a while. Your example is probably using the b...
by drleviathan
Tue Oct 11, 2022 3:51 pm
Forum: General Bullet Physics Support and Feedback
Topic: Correct way to simulate joint friction and joint damping
Replies: 1
Views: 274

Re: Correct way to simulate joint friction and joint damping

You're asking in the General Bullet Physics forum which is mostly about Bullet's core C++ library. You are more likely to get answers to your question if you ask in the PyBullet Support and Feedback forum.
by drleviathan
Mon Oct 10, 2022 2:22 pm
Forum: General Bullet Physics Support and Feedback
Topic: why do btRigidBody objects land on ground on thin edge?
Replies: 2
Views: 591

Re: why do btRigidBody objects land on ground on thin edge?

In Bullet dynamic objects will be deactivated if their linear and angular speeds are below some thresholds for at least 2 seconds. When the sleeping thresholds are too high, or when there is too much damping or energy loss (low restitution), it is possible for objects to balance long enough to be de...
by drleviathan
Sun Sep 11, 2022 2:38 pm
Forum: General Bullet Physics Support and Feedback
Topic: Synchronizing Client Server Physics
Replies: 6
Views: 3017

Re: Synchronizing Client Server Physics

The code comments offer some hints: ·///m_interpolationWorldTransform is used for CCD and interpolation ·///it can be either previous or future (predicted) transform ·btTransform m_interpolationWorldTransform; ·//those two are experimental: just added for bullet time effect, so you can still apply i...
by drleviathan
Tue Sep 06, 2022 2:38 pm
Forum: General Bullet Physics Support and Feedback
Topic: Squishy Physics?
Replies: 12
Views: 3478

Re: Squishy Physics?

Yes, you can reduce the fixedTimeStep . The declaration of btDiscreteDynamicsWorld::stepSimulation() is as follows: virtual int stepSimulation(btScalar timeStep, int maxSubSteps = 1, btScalar fixedTimeStep = btScalar(1.) / btScalar(60.)); The default fixedTimeStep is 1/60th of a second. If you suppl...
by drleviathan
Tue Aug 30, 2022 1:05 pm
Forum: General Bullet Physics Support and Feedback
Topic: Isuue in computing shortest distance between the cone and sphere
Replies: 2
Views: 404

Re: Isuue in computing shortest distance between the cone and sphere

The comment on this line seems incorrect to me: tr[0].setOrigin(btVector3(0, 0, -1)); // centre of the base circle of the cone I would expect the transform supplied to the btGjkPairDetector::ClosestPointInput() to be that of the shape's origin (its center of mass (COM)), not to be that of a point on...
by drleviathan
Mon Aug 15, 2022 3:49 pm
Forum: General Bullet Physics Support and Feedback
Topic: btCollisionWorld::convexSweepTest Performance Implications On Switch
Replies: 1
Views: 617

Re: btCollisionWorld::convexSweepTest Performance Implications On Switch

I too have seen high CPU costs when sweeping against btBvhTriangleMeshShape . This is what I remember: (1) Make sure your mesh is actually using a Boundary Volume Hierarchy. The current version of the btBvhTriangleMeshShape ctor I'm seeing looks like this: btBvhTriangleMeshShape(btStridingMeshInterf...
by drleviathan
Fri Aug 12, 2022 1:56 pm
Forum: General Bullet Physics Support and Feedback
Topic: Any better documentation?
Replies: 2
Views: 512

Re: Any better documentation?

According to the ammo.js github README there exists an IRC channel for discussion: Discussion takes place on IRC at #emscripten on Mozilla's server (irc.mozilla.org) You might be able to get help there. Since javascript must be downloaded before the page is fully working it is common practice to sho...
by drleviathan
Sat Aug 06, 2022 2:32 pm
Forum: General Bullet Physics Support and Feedback
Topic: Detecting collisions with btHeightfieldTerrainShape
Replies: 4
Views: 665

Re: Detecting collisions with btHeightfieldTerrainShape

Yes, if you want to prevent the collisions in the first place you would need to look ahead, with ray-trace or some other mechanism. If you're running several hundred at once then the ray-trace seems like the cheapest approach. Rumor has it the btHeightfieldTerrainShape can get expensive if you make ...
by drleviathan
Fri Aug 05, 2022 10:41 pm
Forum: General Bullet Physics Support and Feedback
Topic: Detecting collisions with btHeightfieldTerrainShape
Replies: 4
Views: 665

Re: Detecting collisions with btHeightfieldTerrainShape

The way collision works in Bullet is... The "broad-phase" provides collision candidates (e.g. pairs bodies with overlapping bounding boxes) to the "narrow-phase" which computes the details (contact manifold) of the collision. Your problem is... you are tapping into the output of ...
by drleviathan
Mon Jul 25, 2022 3:36 pm
Forum: General Bullet Physics Support and Feedback
Topic: VR compilation error
Replies: 3
Views: 783

Re: VR compilation error

AFAICT it does indeed expect four arguments: B3_SHARED_API int b3PhysicsParamSetGravity(b3SharedMemoryCommandHandle commandHandle, double gravx, double gravy, double gravz); Check its declaration in the header to make sure: examples/SharedMemory/PhysicsClientC_API.h What version of the repository is...
by drleviathan
Thu Jul 21, 2022 3:11 pm
Forum: General Bullet Physics Support and Feedback
Topic: Rendering Issues when importing urdf linked to .obj
Replies: 1
Views: 577

Re: Rendering Issues when importing urdf linked to .obj

You might want to try asking in the python-specific forum. This is the support thread for underlying C++ library.
by drleviathan
Thu Jul 21, 2022 3:10 pm
Forum: General Bullet Physics Support and Feedback
Topic: Rendering Only Specific Objects in Camera
Replies: 1
Views: 361

Re: Rendering Only Specific Objects in Camera

You might want to try asking in the python-specific forum. This is the support thread for underlying C++ library.
by drleviathan
Wed Jun 29, 2022 2:54 am
Forum: General Bullet Physics Support and Feedback
Topic: Skeletal Animation
Replies: 1
Views: 738

Re: Skeletal Animation

Here are some scenarios of increasing complexity: (1) Kinematic character always collides like a capsule (or some other simple shape) regardless of their animation state. (2) Dynamic character always collides like a capsule (or some other simple shape) regardless of their animation state. (3) Charac...
by drleviathan
Mon May 30, 2022 3:38 pm
Forum: General Bullet Physics Support and Feedback
Topic: wrong collide result
Replies: 3
Views: 1031

Re: wrong collide result

You're probably experiencing the collision margin of some convex-convex shape collisions. There is an old video on YouTube that illustrates margin.