Real-Time Physics Simulation Forum

I had observed that friction appeared to be less stable in Bullet than in ODE or PhysX for a given friction coefficient. To convince myself of this I created a simple test case consisting of a 10 degree angled ramp with some small boxes to slide down the ramp. Each box has a mass of 1kg and dimensio...

lunkhound wrote:On the graph coloring constraint solver, I may take a crack at that. I'd really like to see that too.

Yes please! I'd love to see this added.

What is the type of your level geometry (in particular, what is the geometry type for your rings)?

You need to remove and re-add the rigid body to the world.

I don't know if this project is active anymore, but I sometimes get crashes when using constraints that can be constrained against the world. In such cases, Bullet actually constrains the rigid body against what it calls a "fixed body" - see btTypedConstraint::getFixedBody(). The fixed bod...

Have you tried using btTriangleShape rather than btConvexTriangleMeshShape? Using btConvexTriangleMeshShape will cause the Convex-Convex collision algorithm to be used. I don't know the inner workings of the GJK-EPA algorithm and so I don't know whether it supports zero volume convex shapes. But if ...

Use btQuaternion::setEuler, btQuaternion::setRotation, or the two corresponding constructors to properly initialize your quaternion. As drleviathan said, only unit quaternions represent rotations. The vector part of the quaternion (x, y, z), also referred to as the imaginary part, are not the Euler ...

I have been having some issues where spheres would fall through large boxes (one side > 1000 units). After a little investigation I found that the sphere-box algorithm is disabled (buggy?) and so I think that the GJK/EPA implementation is currently being used. So, in case anyone is interested, here ...

Looks good. I noticed today that the m_index0 and m_index1 fields don't work as assumed when the compound contains gImpact trimesh shapes. I logged this on github: https://github.com/bulletphysics/bullet3/issues/588
I think your solution should work in this case also.

I'm fairly sure that you don't. Well, at least I haven't needed to in my test cases.

Yes, you should get contact points even when the other object's collision shape is completely inside of your box collision shape. To be clear, the collision detection detects when pairs of shapes are overlapping/intersecting. This includes cases where one shape completely encompasses another.

You should get contact points when one shape intersects with another, either partially or fully. From the btPersistentManifold you can get the pair of collision objects involved. Unless I have misunderstood what you're after, this is really very simple. You can use contactTest, which executes outsid...

Does anyone know why the size of the AABBs pulsate when the associated rigid body is rotating? For example, the size of the AABB for a capsule will oscillate when the capsule is just rolling on its side. See also the following video of a kinematic body with just a cylinder collision shape: https://g...

Ah, ok. I'm coming from ODE which has kind of an inverse relationship to Bullet, where Geoms (collision shapes) "have" a rigid body rather than the other way round. Because of this I chose to enforce that collision shapes belong to at most one collision object. Hence I wouldn't have any is...

I'm interested in this also. It's been at the back of my head and I haven't really thought about it much.
Would it not be more simple to just store a pointer to the collision shape in btManinfoldPoint? Storing indices and then traversing the compound tree just seems to add a lot of unnecessary work.