Search found 26 matches

by colinvella
Fri Nov 07, 2008 2:53 pm
Forum: General Bullet Physics Support and Feedback
Topic: How to prevent floating inactive objects?
Replies: 6
Views: 5623

Re: How to prevent floating inactive objects?

Erwin,

What are the conditions in which you trigger activation? Is it just when an active body hits an inactive one, or do you handle separation as well?
by colinvella
Wed Oct 01, 2008 5:03 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Simulation of inextensible cloth
Replies: 9
Views: 6260

Re: Simulation of inextensible cloth

My gut feeling is that a triangular or quad mesh with perfectly rigid distance constraints will end up bending only along the edges, corresponding to the tri or quad edges, provided that the elements are regular such that collinear edges may be found along the cardinal tri or quad edge directions. T...
by colinvella
Wed Oct 01, 2008 4:55 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: what does "sweep" and "prune" mean ?
Replies: 5
Views: 5212

Re: what does "sweep" and "prune" mean ?

I've seen this algorithm also termed as "sort and sweep" which would imply that "sort" is being used as an alias for "prune". So off the top of my head I'd say that "prune" refers to the sorting of the projection ranges along one or more axes, while "swee...
by colinvella
Sun Sep 28, 2008 1:30 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Polygon soup with polygon soup collision detection
Replies: 5
Views: 4118

Re: Polygon soup with polygon soup collision detection

I have so far tried pre-computing penetration depths (positive inside, negative outside) and associated normals for the eight vertices of each AABB node constituting the BVH I am using to organise the triangles. For each vertex I basically locate the closest enclosed triangle and use its distance fr...
by colinvella
Thu Sep 25, 2008 8:54 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Polygon soup with polygon soup collision detection
Replies: 5
Views: 4118

Polygon soup with polygon soup collision detection

I have a polygon soup geometry object whose elemental triangles are organised using a BVH. I have implemented reasonably robust collision detection code with boxes, spheres, cylinders and even convex polyhedrons, based on the fact that the latter geometry is a fully closed oriented manifold for whic...
by colinvella
Tue Aug 05, 2008 3:32 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: pool ball hitting cushion
Replies: 1
Views: 2887

Re: pool ball hitting cushion

The friction law you are applying is known for increasing the energy of a system in some cases. Try using lower coefficients of restitution and friction. Alternatively, you can also try computing the energy before and after the collision, and lower the velocity accordingly. If your linear and angula...
by colinvella
Tue Jun 03, 2008 10:11 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Contact Manifold question
Replies: 1
Views: 2333

Re: Contact Manifold question

In my own physics engine implementation I sample 8 points on the cylinder end circumference hoping to get a reasonably shaped manifold when placing a cylinder on a box. Seems to work ok in practice.
by colinvella
Tue Apr 22, 2008 2:50 pm
Forum: General Bullet Physics Support and Feedback
Topic: A newbie question: Friction problems?
Replies: 4
Views: 3789

Re: A newbie question: Friction problems?

Assuming you have polyhedral geometry (like the cubes in your case), you could try building a simple aerodynamic model as follows: For every face: 1) compute a face centroid.. for a triangular face this can by done by taking the mean of the vertices 2) compute the body's velocity at the centroid 3) ...
by colinvella
Mon Apr 14, 2008 3:26 pm
Forum: General Bullet Physics Support and Feedback
Topic: Raycast Vehicle and arcade drift
Replies: 14
Views: 14447

Re: Raycast Vehicle and arcade drift

Is centripetal force in your example the same thing as applyTorque()? And how is applyTorque() different from setAngularVelocity()? Also, does applyTorque() use the center of mass to apply the torque around? "outward from the curved path while turning". I am not sure how to translate that...
by colinvella
Thu Apr 10, 2008 10:36 am
Forum: General Bullet Physics Support and Feedback
Topic: Raycast Vehicle and arcade drift
Replies: 14
Views: 14447

Re: Raycast Vehicle and arcade drift

You could try keeping high wheel friction (to prevent over-realistic drifting) and instead apply a centripetal force at the car's centre of mass, outward from the curved path while turning. The magnitude of this force could be calculated as a function of linear and angular speed and triggered after ...
by colinvella
Wed Mar 26, 2008 10:28 am
Forum: Non-technical forum and license/patent discussion
Topic: Cannot persist login on forum
Replies: 6
Views: 23536

Re: Cannot persist login on forum

If that's the cause it could be due to a config parameter getting reset during the upgrade.
by colinvella
Tue Mar 25, 2008 10:54 am
Forum: Non-technical forum and license/patent discussion
Topic: Cannot persist login on forum
Replies: 6
Views: 23536

Cannot persist login on forum

I'm not sure if this is the right place to post this, as it is a problem related to the forum software itself rather than Bullet. I am unable to stay logged in even when I tick the "Log me in automatically" checkbox - I am required to log in every time. I tried this on both IE7 and Firefox...
by colinvella
Thu Mar 13, 2008 11:54 am
Forum: General Bullet Physics Support and Feedback
Topic: Bullet on networks
Replies: 6
Views: 3946

Re: Bullet on networks

Yes.. obviously with the downsides I highlighted.
by colinvella
Wed Mar 12, 2008 2:23 pm
Forum: General Bullet Physics Support and Feedback
Topic: Bullet on networks
Replies: 6
Views: 3946

Re: Bullet on networks

What about a partial approach, that is, just solving unconstrained motion? Arguably you might see jittering or even temporary tunnelling if lag times are large enough, but at least you should be able to get fluid motion between status updates.
by colinvella
Thu Mar 06, 2008 1:01 pm
Forum: General Bullet Physics Support and Feedback
Topic: Moving character to avoid collision
Replies: 7
Views: 6074

Re: Moving character to avoid collision

I don't wish to deviate this topic further, so I'll close by saying it really looks very impressive and is very reminiscent of the original (missile-equipped jeep, chopper, RIB, submarine inflitration etc.). I wish you guys the best of luck! :)