Search found 861 matches

by Dirk Gregorius
Thu Dec 17, 2015 10:10 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Collision response - solver, penetration recovery
Replies: 21
Views: 47066

Re: Collision response - solver, penetration recovery

I think you need to add friction from what you are describing. If you still see jitter after this make sure that the penetration recovery is not overshooting.
by Dirk Gregorius
Wed Dec 09, 2015 6:26 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Collision response - solver, penetration recovery
Replies: 21
Views: 47066

Re: Collision response - solver, penetration recovery

A notable thing that is often overlooked is that Baumgarte for force based steppers is applied before the discretization, and for impulse based steppers it applied after. Tweaking Baumgarte is usually pretty difficult and it is even harder for force based steppers from my experience. I personally pr...
by Dirk Gregorius
Fri Dec 04, 2015 5:34 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Collision response - solver, penetration recovery
Replies: 21
Views: 47066

Re: Collision response - solver, penetration recovery

You first create contact points as you describe using e.g. SAT or any other method of choice. Then (in the solver) you create usually one non-penetration constraint and two friction constraints per contact point. While the contact point contains all geometrical information (position, normal, penetra...
by Dirk Gregorius
Fri Sep 04, 2015 2:33 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: rotation collision response?
Replies: 7
Views: 11459

Re: rotation collision response?

You apply equal and opposite impulses at each contact point. Each off center impulse will indeed affect the angular velocity. I don't want to sound offensive, but you might want to study some basic rigid body mechanics before trying to implement a physics engine.
by Dirk Gregorius
Thu Sep 03, 2015 5:51 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: rotation collision response?
Replies: 7
Views: 11459

Re: rotation collision response?

It looks as if a cross product is missing. It should be r x n. Here is a good derivation:
http://www.essentialmath.com/AngularImpulse.pdf
by Dirk Gregorius
Thu Aug 06, 2015 7:01 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Persistent Manifold & Contact breaking threshold
Replies: 4
Views: 12443

Re: Persistent Manifold & Contact breaking threshold

I think what you describe is a natural limitation of the incremental manifold. There will always be a situation where your thresholds break and you end up with one contact point. For many use cases (e.g. debris) this is no problem. Alternatively you can also use GJK and clipping to build the full ma...
by Dirk Gregorius
Sun May 31, 2015 8:35 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Bilateral advancement 3D GJK feature extraction problems
Replies: 12
Views: 31059

Re: Bilateral advancement 3D GJK feature extraction problems

I am glad you like those. Maybe I should give a breakdown talk how to model joints using constraints next year. Similar to the contact talk last year.

I had a look at a video of Supraleiter. This looks great! Good luck with your project!
by Dirk Gregorius
Sat May 30, 2015 6:16 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Bilateral advancement 3D GJK feature extraction problems
Replies: 12
Views: 31059

Re: Bilateral advancement 3D GJK feature extraction problems

I use variant 2. I don't understand variant 1. If you have Edge/Face or Face/Face every vertex of the edge/otherFace has the same distance to the reference face. I think averaging might be fine as well, but not sure if this solves any problem How are you evaluating the separation function? In Box2D ...
by Dirk Gregorius
Fri May 29, 2015 8:57 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Bilateral advancement 3D GJK feature extraction problems
Replies: 12
Views: 31059

Re: Bilateral advancement 3D GJK feature extraction problems

I only have Vertex/Vertex, Vertex/Edge, Vertex/Face and Edge/Edge. Edge/Face and Face/Face are handled as Vertex/Face. This makes the dispatch easy.

No, I would not add this to GJK. I personally keep my GJK as simple and clean as possible. Especially since the dispatch is trivial.
by Dirk Gregorius
Thu May 28, 2015 9:27 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Bilateral advancement 3D GJK feature extraction problems
Replies: 12
Views: 31059

Re: Bilateral advancement 3D GJK feature extraction problems

I look at the vertex count of the simplex and also the unique count as you describe: int VertexCount = Cache.VertexCount. int UniqueCount1 = rnUniqueCount( Cache.VertexCount, Cache.Vertices1 ); int UniqueCount2 = rnUniqueCount( Cache.VertexCount, Cache.Vertices2 ); Then I dispatch as follows: if ( V...
by Dirk Gregorius
Thu May 28, 2015 5:18 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Bilateral advancement 3D GJK feature extraction problems
Replies: 12
Views: 31059

Re: Bilateral advancement 3D GJK feature extraction problems

Do you expect us to read your code and find the bug for you? If you ask some concrete question I might be able to help.
by Dirk Gregorius
Tue Mar 17, 2015 4:51 pm
Forum: General Bullet Physics Support and Feedback
Topic: Rotating rigidbody to face direction of another rigidbody
Replies: 6
Views: 9535

Re: Rotating rigidbody to face direction of another rigidbod

This is often called the shortes arc quaternion. There should be a function called shortesArcQuaternion() in Bullet based on Stan Melax article in one of the GPG. Here is another good disussion: http://stackoverflow.com/questions/1171849/finding-quaternion-representing-the-rotation-from-one-vector-t...
by Dirk Gregorius
Tue Mar 10, 2015 5:18 pm
Forum: Links, Papers, Libraries, Demos, Movies, Comparisons
Topic: Rubikon : Valve's physics engine for Source 2
Replies: 8
Views: 70020

Re: Rubikon : Valve's physics engine for Source 2

I gave three talks over the last three years at GDC which describe essentially the Rubikon collision pipeline. I am thinking to give a talk on mesh and continuous contacts next year and then close with a talk about the solver following this. The solver is essentially SI with post-projection, but the...