Real-Time Physics Simulation Forum

Erwin Coumans wrote: ↑Wed Nov 01, 2006 2:56 pm You should not set the linear velocity for static objects. Only dynamic and/or kinematic objects can ever move.
Thanks,
Erwin

I have a question. What is the meaning of setting velocity on a kinematic body? The world will not move this body, only user code, correct?

Thanks,
Morgan

I've read that creating a hierarchy of btCompoundShapes should work, but I'm having an issue with it. My tree looks like this: btCompoundShape / | \ (btSphereShape, btCompoundShape) (btSphereShape, btCompoundShape) (btSphereShape, btCompoundShape) | | | (btSphereShape, btCompoundShape) (btSphereShap...

Thank you!

That makes sense... sneaky. This language is no nuanced.

Here is what I have found. Recall my face/triangle and vertex data are declared in the GeometryElement class interface as: std::vector<Vertex> _vertices; std::vector<Face> _faces; const std::vector<Vertex>& vertices() const; const std::vector<Face>& faces() const; I find that if I reference ...

I am trying to create static physics bodies using btBvhTriangleMeshShape . This works fine if I copy vertex data into btTriangleMesh , and use that to create a btBvhTriangleMeshShape . However, copying is obviously not desirable. The approach I am currently trying is: Describe vertex layout using bt...

GOT IT. rollingFriction needs to be 0. Apparently this parameter is there to allow things to not roll indefinitely.... (like pool balls): "the m_rollingFriction prevents rounded shapes, such as spheres, cylinders and capsules from rolling forever." I had (incorrectly) assumed it was kineti...

I just tried the margin at 0 again but without luck. :\ I also did two other things: 1. Dropped a fresh source clone from the bullet repo into my extern/ directory and re-build the project (can't believe it built without CMake mods!). No change in behavior. 2. Instead of relying on a bunch of abstra...

Thanks... plugged that in to replace my existing function:

mat4 GLMMat4FromBTTransform(const btTransform& from) {
mat4 glmMat;
from.getOpenGLMatrix(value_ptr(glmMat));
return glmMat;
}

Exacto-el-same-o.

Thanks Chip. Probably a good idea.

I think I will try managing the physics simulation from the "client side" of my framework (as opposed to opaquely through a wrapper) first, then start from scratch. Weird stuff.

A little more info... Everything with configuring the world, creating shapes and rigid bodies, and configuring those objects all seems to be by the book... There are only two things that I am somewhat concerned about: 1. For resource management and scene graph synchronization purposes, I'm storing b...

Hi Mwni, Unfortunately timestep & number of substeps don't appear to be the issue. Since the simulation appears to run much more stably with very high masses (10,000x scale) I'm tempted to just move forward with that. I'm wondering what types unforeseen issues scaling the mass for all my objects...

Chip, my code appears to do essentially all the same things as yours, except that I calculate localInertia like this: btVector3 localInertia = {0, 0, 0} collisionShape->calculateLocalInertia(mass, localInertia); Note sure if that's correct... If I try it with your random method of calculating localI...

Another example using boxes. The spinning phenomenon is a lot less common, but boxes often don't lay flat on the ground. btBoxShape, mass=1

Hi Mwni, I played around with m_numIterations a bit. Setting to 0 results in no dynamic<->static interaction as expected, but anything larger seems to have no effect. m_numIterations = 0: http://goosesensor.net/bt_5.gif m_numIterations = 10: http://goosesensor.net/bt_6.gif m_numIterations = 100: htt...

Thanks chip.

Generally activiationState gets set to ACTIVE_TAG when the rigid body is created in my code -- I disabled it to leave it as Bullet's default, then changed the friction and restitution settings as you recommended. Here is the result: