Search found 495 matches

by drleviathan
Tue Apr 16, 2019 8:45 pm
Forum: General Bullet Physics Support and Feedback
Topic: Model Scaling
Replies: 10
Views: 317

Re: Model Scaling

I dunno. The tunnelling problem is a fundamental issue for physics simulations. You need to understand it and tweak your simulation or your content to solve it. I'm sure it is solvable. Answer these questions and maybe someone here will have an idea: What are the dimensions of your objects? How big ...
by drleviathan
Tue Apr 16, 2019 8:25 pm
Forum: General Bullet Physics Support and Feedback
Topic: Elastic Constraints
Replies: 1
Views: 75

Re: Elastic Constraints

How does the sphere move so quickly? Via a collision or do you slam its position/velocity through some non-physical logic? Is it kinematic? I'm asking because if you are moving the Sphere in a violent and non-physical way I could see how a constraint would have trouble keeping up. And if you're doin...
by drleviathan
Mon Apr 15, 2019 5:26 pm
Forum: General Bullet Physics Support and Feedback
Topic: Model Scaling
Replies: 10
Views: 317

Re: Model Scaling

Have you enabled continuous collision detection (CCD) on the small moving objects? It definitely helps solve the tunnelling problem but my experience has been: it doesn't fix it completely. To enable CCD you set the radius of the proxy sphere and a minimum motion delta at which to use CCD. For decen...
by drleviathan
Tue Apr 02, 2019 12:40 pm
Forum: General Bullet Physics Support and Feedback
Topic: Propagating collisions in a mixed chain Dynamic/Kinematic
Replies: 7
Views: 476

Re: Propagating collisions in a mixed chain Dynamic/Kinematic

Yeah, my simplistic idea wouldn't work when the Blue object is a collection of hinged RigidBodies or a MultiBody. I think you did a good job of listing your options in the other post. I don't have much experience with MultiBody but the path that appeals to me would be (2) where the vehicle and its a...
by drleviathan
Fri Mar 29, 2019 3:34 pm
Forum: General Bullet Physics Support and Feedback
Topic: Propagating collisions in a mixed chain Dynamic/Kinematic
Replies: 7
Views: 476

Re: Propagating collisions in a mixed chain Dynamic/Kinematic

One Shape can be shared across multiple RigidBodies but they only represent the geometry to use in local collision checks, not the world-frame object. The two "collision shapes" you see in your debug rendering are the two RigidBodies which just happen to have the same Shape. I still don't understand...
by drleviathan
Wed Mar 27, 2019 4:34 pm
Forum: General Bullet Physics Support and Feedback
Topic: Propagating collisions in a mixed chain Dynamic/Kinematic
Replies: 7
Views: 476

Re: Propagating collisions in a mixed chain Dynamic/Kinematic

Why must the blue group be kinematic? Presumably you need it to follow some scripted path. Perhaps you could use a dynamic RigidBody with a btCompoundShape for the blue group and make it follow the same path close enough via a custom btActionInterface. Since the action would be applied after collisi...
by drleviathan
Thu Mar 21, 2019 6:56 pm
Forum: General Bullet Physics Support and Feedback
Topic: Importing multiple objects in one obj.-file
Replies: 1
Views: 148

Re: Importing multiple objects in one obj.-file

I believe that is the intended behavior. The OBJ file is used to describe the btShape of a btCollisionObject. In other words, the two "objects" in the OBJ file are interpreted as distinct convex parts (subshapes) of a btCompoundShape. This provides an easy way to build "concave" shapes which are rea...
by drleviathan
Wed Mar 20, 2019 3:54 pm
Forum: General Bullet Physics Support and Feedback
Topic: change position static object... SOLVED
Replies: 3
Views: 208

Re: change position static object...

In my experience slamming the static RigidBody's WorldTransform just works . It is puzzling that it isn't working for you. However, if you've called world->setForceUpdateAllAabbs(false) for runtime optimization then you have to remember to world->updateSingleAabb(rigidBody) after moving it for colli...
by drleviathan
Tue Mar 19, 2019 4:14 pm
Forum: General Bullet Physics Support and Feedback
Topic: contactPairTest problem with object inside another object
Replies: 2
Views: 244

Re: contactPairTest problem with object inside another object

The ContactResultCallback::addSingleResult() is only called when an actual ManifoldContactPoint is added to the ContactManifold. Therefore it must be the case that no points are being added when one object is completely inside the other. What btCollisionShape are you using for the outer btCollisionO...
by drleviathan
Fri Feb 15, 2019 5:20 pm
Forum: General Bullet Physics Support and Feedback
Topic: rotate a crate around me when i Turn
Replies: 4
Views: 308

Re: rotate a crate around me when i Turn

Sorry that code doesn't work. I haven't had time to actually setup a bt6dofConstraint to test, debug, and fix. Yes, characterToWorld would be worldToCharacter.inverse() . Order matters for transforms because they don't commute, so what is the right order? A useful trick I use is to imagine the trans...
by drleviathan
Sun Feb 10, 2019 7:16 pm
Forum: General Bullet Physics Support and Feedback
Topic: rotate a crate around me when i Turn
Replies: 4
Views: 308

Re: rotate a crate around me when i Turn

The btGeneric6DofConstraint class has two CTORs: btGeneric6DofConstraint(btRigidBody& rbA, btRigidBody& rbB, const btTransform& frameInA, const btTransform& frameInB ,bool useLinearReferenceFrameA); btGeneric6DofConstraint(btRigidBody& rbB, const btTransform& frameInB, bool useLinearReferenceFrameB)...
by drleviathan
Wed Feb 06, 2019 4:18 pm
Forum: General Bullet Physics Support and Feedback
Topic: performance of collisions of 'voxel' shapes
Replies: 6
Views: 648

Re: performance of collisions of 'voxel' shapes

BTW, are you sharing one btBoxShape instance for all of the subshapes? Or are you creating a new instance for each?

I've never not shared and am curious to know how noticeable would be the performance difference between the two cases.
by drleviathan
Sun Feb 03, 2019 2:37 am
Forum: General Bullet Physics Support and Feedback
Topic: Combining collision flag
Replies: 2
Views: 305

Re: Combining collision flag

Combining those two flags should work fine, however if you're changing the MotionType from STATIC to KINEMATIC then you need to first remove the body from the World and re-add it. You can't change between those two MotionTypes on the fly because the bodies live on distinct internal lists inside the ...
by drleviathan
Sun Feb 03, 2019 2:30 am
Forum: General Bullet Physics Support and Feedback
Topic: performance of collisions of 'voxel' shapes
Replies: 6
Views: 648

Re: performance of collisions of 'voxel' shapes

I've noticed the same performance problem: a medium number of btCompoundShapes, each with a medium number of subshapes all colliding together can slow down the stepSimulation() call. As I recall my example was only about 20 objects, each with about 18 subshapes. It didn't slow down to 2Hz, but the s...
by drleviathan
Sat Feb 02, 2019 3:51 pm
Forum: General Bullet Physics Support and Feedback
Topic: Getting the direction an object would move
Replies: 1
Views: 238

Re: Getting the direction an object would move

Here is method might work for you. It does have a theoretical side-effect on the "pushing" objects : they will lose momentum as if they really did move the "non-movable" objects. Also, it would require your non-movable objects to be "active" in the simulation, which will "activate" other objects tha...