Search found 756 matches

by drleviathan
Fri Nov 26, 2021 5:23 pm
Forum: General Bullet Physics Support and Feedback
Topic: Linux, make fails
Replies: 3
Views: 829

Re: Linux, make fails

For best results: use the cmake. I meant: don't use the premake build scripts: stick with cmake . Hrm... I'm not seeing any Test_BulletCollision targets in the cmake configs. When I hunt around I find in test/collision/CMakeLists.txt there is a Test_Collision target. What version of Bullet do you t...
by drleviathan
Fri Nov 26, 2021 4:28 pm
Forum: General Bullet Physics Support and Feedback
Topic: btGeneric6DofConstraint - Weld/Parent
Replies: 6
Views: 394

Re: btGeneric6DofConstraint - Weld/Parent

You could try taking smaller substeps. The more times the simulation "solves" a system of constraints the more rigid it will be. This is fundamentally why a system of constraints gets wobbly: the Bullet constraint solver will only iterate so many times before it concludes "good enough...
by drleviathan
Fri Nov 26, 2021 4:05 pm
Forum: General Bullet Physics Support and Feedback
Topic: About the size of triangles and objects
Replies: 5
Views: 372

Re: About the size of triangles and objects

It is OK for Bullet bodies to larger than 100 units. In particular: it is OK for static or relatively slow kinematic objects to be very large (100s or 1000s of units) however be careful when making very large (>100 units) dynamic objects or fast moving kinematic . Basically, if you have very large f...
by drleviathan
Thu Nov 25, 2021 4:47 pm
Forum: General Bullet Physics Support and Feedback
Topic: About the size of triangles and objects
Replies: 5
Views: 372

Re: About the size of triangles and objects

You definitely don't want to use shapes as small as 0.01 meters. Bullet is effectively hard-coded to work best for dynamic objects on the order of a few tenths of a meter to a few tens of meters. That is: assumptions are made in the default parameters and logic that make it problematic to wander out...
by drleviathan
Sat Nov 20, 2021 3:23 pm
Forum: General Bullet Physics Support and Feedback
Topic: Toroidal Universe, as found in Asteroids (1978)
Replies: 1
Views: 156

Re: Toroidal Universe, as found in Asteroids (1978)

Wrap around boundary conditions are not a feature of Bullet. Not that it isn't possible... but I can't think of any easy way to do it. All of the schemes I come up with involve complex negotiations between proxy objects. In other words, you wouldn't really have one object spanning the top and bottom...
by drleviathan
Fri Nov 19, 2021 6:58 am
Forum: General Bullet Physics Support and Feedback
Topic: Squishy Physics?
Replies: 10
Views: 496

Re: Squishy Physics?

Re: pile of objects... you are putting too many into a state of penetration. The penetration resolution logic works well for two overlapping objects but less well for N simultaneously overlapping objects, because it tries to separate them by pairs and alternate pairs can work against each other. You...
by drleviathan
Thu Nov 18, 2021 2:54 pm
Forum: General Bullet Physics Support and Feedback
Topic: Squishy Physics?
Replies: 10
Views: 496

Re: Squishy Physics?

So this means, if you don't override the two optional arguments then your steps will only ever do one substep at 1/60th of a second. This is fine if you call stepSimulation() with timeStep < substep: on some calls the stepSimulation will do nothing but accumulate time and then once it has a full su...
by drleviathan
Thu Nov 18, 2021 5:23 am
Forum: General Bullet Physics Support and Feedback
Topic: Squishy Physics?
Replies: 10
Views: 496

Re: Squishy Physics?

I've never used btConvexTriangleMeshShape before but since it is convex I assume the GJK algorithm is supported for dynamic objects. You might try using btConvexHullShape to see if that helps you, but I don't expect this to change anything. Ideally the VHACD decomposition is giving you only 8 points...
by drleviathan
Wed Nov 17, 2021 3:10 pm
Forum: General Bullet Physics Support and Feedback
Topic: Squishy Physics?
Replies: 10
Views: 496

Re: Squishy Physics?

So... how do you compute timeStep ? Is it a constant or do you measure it? If you measure it: how big does it get? The gap between boxes is not caused by the AABB. In any case: if you are using btBoxShape and you aren't explicitly overriding the AABB then it is difficult to imagine how the AABB coul...
by drleviathan
Tue Nov 16, 2021 5:06 pm
Forum: General Bullet Physics Support and Feedback
Topic: Squishy Physics?
Replies: 10
Views: 496

Re: Squishy Physics?

It looks to me as if the boxes are going into a state of penetration before the system realizes they should be colliding. The penetration resolution logic then kicks in and pushes them apart. (1) Perhaps the AABB of the boxes is just wrong (too small): by the time the broadphase figures out the AABB...
by drleviathan
Tue Nov 09, 2021 4:40 pm
Forum: General Bullet Physics Support and Feedback
Topic: Can't get rotation from applyForce's rel_pos
Replies: 1
Views: 334

Re: Can't get rotation from applyForce's rel_pos

I would expect the object to rotate after your applyForce() call. However, applyForce() only lasts for one substep so if you don't call it multiple times over several substeps it is possible your body won't pick up enough angular velocity to notice. The delta angular velocity from a single applyForc...
by drleviathan
Thu Oct 28, 2021 6:19 pm
Forum: General Bullet Physics Support and Feedback
Topic: Setting Up Attracting Force Between Bodies
Replies: 2
Views: 381

Re: Setting Up Attracting Force Between Bodies

A few things: (1) You might have more success if you move your question to the PyBullet Support and Feedback section of this forum. This General Biullet Physics Support and Feedback section is more about the C++ API. (2) Are you sure you want to perform your simulation using PyBullet rather than C++...
by drleviathan
Tue Oct 26, 2021 12:07 am
Forum: General Bullet Physics Support and Feedback
Topic: Collision Shape From FBX SDK Vertices
Replies: 3
Views: 442

Re: Collision Shape From FBX SDK Vertices

Sorry, I misunderstood the collision problems you were describing: it sounded like the mesh objects were moving around. I re-read your post more carefully and offer this numerated summary of the problems you are experiencing, with some re-wording for clarity. If I got any of these wrong please offer...
by drleviathan
Mon Oct 25, 2021 3:07 pm
Forum: General Bullet Physics Support and Feedback
Topic: Collision Shape From FBX SDK Vertices
Replies: 3
Views: 442

Re: Collision Shape From FBX SDK Vertices

btBvhTriangleMeshShape only supports static objects, not objects with non-zero velocity. For dynamic objects use btCompoundShape with convex decompositions of your concave shapes, or maybe the GImpactShapes.