Real-Time Physics Simulation Forum

Another source dealing with using Lemke to solve for Nash equilibrium suggested that you could just randomly select a pivot. Well one could store a counter for the system, always initialized to a specific value (like zero). Then every time you need to choose between pivots, increment the counter an...

Looks great! Looking forward to the paper on the constraint fluids. I believe perhaps the wire simulation might be covered in an upcoming book?

Search for motors in Bullet.

1) I don't know what approach is generally used for that type of collision. I have used quadric curved surfaces as height maps (with only vertical feelers), but that's much easier than the general 3-D problem, because colliding a curved surface vs. a triangle can result in multiple contact points. 2...

Angular tracking is significantly more bloated and follows the same principals by trying to minimize local angular error component-wise. To clarify, you are trying to fix up actual vs. desired angular *velocity*? Or actual vs. desired orientation? Or both? I don't know if I can help, I'm not a flig...

I believe what you are looking for is called 'broadphase collision detection', and yes you can typically do better than the O(n^2) algorithm that you suggest, although that is always the worst case. You can probably just search for broadphase on this site to get more info. I believe Bullet uses some...

To narrow it down a bit, I would probably start with the paper "Iterative Dynamics with Temporal Coherence" by Erin Catto. It's short enough to read and understand in a day, and fairly easy to implement, too. After that, I'd probably look at Kenny Erleben's thesis for more details.

1) I don't know. 2) Looks like minor floating point round off. Depending on how you draw the skids, you probably want them to be slightly offset from the surface anyway (slightly above so there's no z-buffer artifacts). 3) Instead of using the wheel's forward vector, I would recommend using its norm...

Looks good, and I'm sure we're all interested in hearing more about your new solver!

Hi, I'm looking at this article about the Pacejka's tire model: http://www.racer.nl/reference/pacejka.htm It computes tire contact forces, but there is no mention about surface type. How to combine pacejka with the fact that it is different whether one rides on the asphalt and on the gravel? The fi...

I think you're missing some sort of restitution coefficient (I don't remember if that is addressed in Catto's paper). With zero restitution, a.k.a. a plastic collision, the contact constraint will simply solve the impulse needed to prevent further penetration ... in other words the resulting velocit...

Sounds good, keep up the hard work!

about coding the pinion-pinion gear constraint, I realize that the rotation velocity vectors of the 2 pinions bodies must be expressed relative to a frame body... does it mean the constraint depends on 3 bodies?? that's funny, assuming that joint constraints usually depend on 1 or 2 bodies... It ne...

YES! I got it! It works! I have the nonholonomic constraint for a gear made up of two wheels, and my algorithms can take care of it. I must compute another kind of gear: one part is a wheel, the other is flat, thus transforming a rotation motion in a translation, and vice versa... I can try to comp...

Tantor wrote:... maybe the gear constraint should be computed in terms of the angular velocity vectors...

Yup.