Real-Time Physics Simulation Forum

A "kinematic" object is movable but moves in a non-physical way. That is, its motion is defined by some external source that is independent from the physics dynamics. Hence, kinematic will pass right through other kinematic and static objects... if the code that dictates their motion says ...

Yes, the character should collide with the tree automatically by default. There must be a bug in your program, but you have not supplied enough information for us to figure out why. You would have to supply some code or a more detailed description of how you build/move the character and tree. Some q...

After reading the btConvexHullShape API I would guess the code you want might look something like this: const btTransform& transform = body->getWorldTransform(); int numPoints = hullShape->getNumPoints(); for (int i = 0; i < numPoints; ++i) { btVector transformedPoint = transform * hullShape->ge...

As per the wiki page about callbacks and triggers you should be able to use the btCollisionWorld::contactPairTest() method. I assume that path is not short circuited by the broadphase collision culling optimizations, but have not actually tried it myself.

As an optimization Bullet does not generate contact manifolds between static objects. You need to make at least one of them dynamic or keyframed. When using btBvhTriangleMeshShape the object MUST be static, so you'll have to use a different shape for any that you make keyframed. See this thread for ...

You also need to set the angular velocity of the kinematic bowl -- the physics engine won't update the bowl's rotation, but collisions with it will pick up velocities at the contact points. In fact, you don't even need to update the bowl's rotation to get the pellets to move -- just set its angular ...

When a ball at rest (inactive) gets hit by a moving object (active) the physics simulation will automatically activate the ball. Real activation triggers (i.e. collisions) in the physics engine are handled properly, however if you were driving the ball with an external trigger (e.g. keyboard) then y...

The simple reason is that I don't believe in perpetual motion machines so I discard such notions without inspection. However, in this specific case: (1) Any spin of the disk about its axis, if any, could only be introduced when the system changes speed about the vertical axis -- that is, when there ...

I don't believe it.

Given some normal vectorB there is an infinite number of rotations (and hence infinite combinations of Euler angles) that would rotate any reference vectorA to it -- there is no unique solution for the information you want. To compute a unique solution you need more information than just the normal,...

What do you really want to do? Are you just using the RX , RY , and RZ values to define a plane? If so then the Euler angles are pnot the most useful info to harvest. A plane can be defined by any point on the plane and a normal. The result of the raycast provides these for you --> no need to do Eul...

The problem, I think, is that you're submitting float s to some class constructors that explicitly require double . The way to avoid this problem is to never use the float type directly and to never use float literals (e.g. 1.0f or 1.23e4f). Instead always use btScalar and always explicitly cast any...

Even though it is the main game entity it should be possible to make it do what you want while allowing it to go inactive in the physics simulation. I would recommend figuring out how to make your game without resorting to setActivationState(DISABLE_DEACTIVATION) . You can activate it directly using...

After thinking about this during my morning commute I decided that a conservation of momentum treatment just won't work. Although the system is driven by an external torque (momentum isn't conserved) I thought maybe the conservation rules could be applied along specific axes -- nope. Then I looked a...

One way to simulate this system would be to use verlet constraints . Each big sphere could be simulated as a large collection of smaller spheres connected by springs. The advantage of such an approach would be: (1) The algorithm is relatively simple to implement. (2) It is stable. (3) It can achieve...