Search found 43 matches
- Mon Sep 18, 2017 8:50 pm
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: Correct Contact Manifold
- Replies: 3
- Views: 49905
Re: Correct Contact Manifold
Hello everyone! How do people finde correct hit points based on analysis of Minkowski difference? 2 algorithms I know of: expanding polytope algorithm (basically quick hull), or minkowski portal refinement. Both algorithms have unattractive qualities. I prefer getting contact points like Dirk prese...
- Sat Sep 09, 2017 9:49 pm
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: Algorithm help / Connecting Centroids
- Replies: 11
- Views: 125604
Re: Algorithm help / Connecting Centroids
You can find your planes by performing plane slicing. Start with a simple convex shape, like an AABB, and slice it with many planes. Something like this: AABB bounds = WrapAllPoints(points, extra_radius); std::vector<ConvexHull> hulls; for (int i = 0; i < points.size(); ++i) { Point a = points[i]; C...
- Thu Sep 07, 2017 10:46 pm
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: Algorithm help / Connecting Centroids
- Replies: 11
- Views: 125604
Re: Algorithm help / Connecting Centroids
I would point out the interior of the bubbles form a 3D Voronoi diagram.
- Thu May 04, 2017 2:04 am
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: Non-linear Gauss-Seidel solver
- Replies: 11
- Views: 113844
Re: Non-linear Gauss-Seidel solver
Wasn't post projection (NGS) sort of hacky? As in J was stolen from the velocity derivation and plugged in to form a psuedo position formula? Description of this by Cline in his nice paper: https://pdfs.semanticscholar.org/476d/fce4be549655938c499663af246702cbc781.pdf. In there it seems J is taken f...
- Fri Apr 14, 2017 5:14 pm
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: Continuous GJK
- Replies: 7
- Views: 26642
Re: Continuous GJK
Yes, the problem is the axis flips. It can flip when the axis goes from penetrating to non-penetrating, and can also flip as the two vectors rotate relative to one another: https://en.wikipedia.org/wiki/Cross_pro ... roduct.gif
- Mon Apr 10, 2017 7:09 pm
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: Continuous GJK
- Replies: 7
- Views: 26642
- Fri Apr 07, 2017 8:01 pm
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: Continuous GJK
- Replies: 7
- Views: 26642
Re: Continuous GJK
We use this technique in Source 2 and it works great. It is not trivial to extend to 3d due to the non-convexity of the edge-edge case though. Would it be possible to elaborate on what the "non-convexity" of edge-edge is? After studying Box2D, it seems like an approach could be to form a ...
- Wed Aug 17, 2016 4:18 pm
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: How to compute BoxBox contact point ?
- Replies: 6
- Views: 15095
Re: How to compute BoxBox contact point ?
They wrote dBoxBox like that because it made sense to them at the time to write it like that. They probably derive a lot of the math on paper and then translated it into code. If you want to know what c1 - k1 - k3 is then you need to go through the math and draw pictures of what everything is. You c...
- Thu May 12, 2016 8:19 pm
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: Steiner's Theorem for Composite Bodies
- Replies: 12
- Views: 34059
Re: Steiner's Theorem for Composite Bodies
Oh I see what you meant. I thought the old post was shifting to COM with a subtraction (I didn't read carefully).
I = I_cm + md^2, d^2 -> always positive, aka the distance from origin matters, and any vector (positive or negative) fixed on the origin will be the same result.
I = I_cm + md^2, d^2 -> always positive, aka the distance from origin matters, and any vector (positive or negative) fixed on the origin will be the same result.
- Thu May 12, 2016 6:00 pm
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: Steiner's Theorem for Composite Bodies
- Replies: 12
- Views: 34059
Re: Steiner's Theorem for Composite Bodies
A 7 year old bug!
- Mon May 02, 2016 12:20 am
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: Steiner's Theorem for Composite Bodies
- Replies: 12
- Views: 34059
Re: Steiner's Theorem for Composite Bodies
Usually inertia tensors are calculated in model space (or local space) of the rigid body. Let's call the rigid body's reference frame A. Say we have a convex hull fixed in A. When A rotates the hull will rotate about A's origin, remaining fixed. When the inertia tensor of the hull is computed the te...
- Tue Feb 16, 2016 10:24 pm
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: Lightweight engine for simulating dice?
- Replies: 4
- Views: 13354
Re: Lightweight engine for simulating dice?
Here's a minimalistic 3D library with only 3D AABB collision detection, that does pretty much exactly what you're asking for and not much else: https://github.com/RandyGaul/qu3e I'm the author of the library, so if you'd still like to implement your own solution I'd be happy to discuss in more detai...
- Thu Aug 06, 2015 3:18 am
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: Persistent Manifold & Contact breaking threshold
- Replies: 4
- Views: 12445
Re: Persistent Manifold & Contact breaking threshold
I myself haven't implemented EPA, but if it's possible to identify the features that produce a point of contact then the caching of data from one point to another can happen through some book-keeping, like a check for matching contact point IDs. This would avoid any annoying threshold tweaking. As f...
- Sat May 30, 2015 5:29 pm
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: Bilateral advancement 3D GJK feature extraction problems
- Replies: 12
- Views: 31063
Re: Bilateral advancement 3D GJK feature extraction problems
IIRC point most penetrating, since that is what we'll want to drive towards 0 penetration with the root solver.
- Fri May 29, 2015 7:28 pm
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: Bilateral advancement 3D GJK feature extraction problems
- Replies: 12
- Views: 31063
Re: Bilateral advancement 3D GJK feature extraction problems
I just enumerated the possibilities with some if-statements and a switch. Perhaps this might add some value to the discussion: http://pastebin.com/WAHSnRqw Also Dirk, I'm curious if you know if anyone has ever placed feature extraction into GJK itself. It seemed to me to be a little silly to do this...