Search found 214 matches

by raigan2
Wed Apr 20, 2022 12:44 pm
Forum: Links, Papers, Libraries, Demos, Movies, Comparisons
Topic: 10 Minute Physics
Replies: 1
Views: 392

10 Minute Physics

I just wanted to put this on everyone's radar: Matthias Muller has been making a really awesome series of tutorials (videos, slides, and source code) working through Position Based Dynamics; a great resource for anyone wanting to implement it. https://matthias-research.github.io/pages/tenMinutePhysi...
by raigan2
Thu Feb 24, 2022 4:23 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Where do you get the data to put in the inertial tag in MuJoCo?
Replies: 1
Views: 1515

Re: Where do you get the data to put in the inertial tag in MuJoCo?

I don't know if this is true (never used MuJoCo) but given the nature of the other data, I suspect "pos" is the position of the center of mass in the local frame. So for a cube it would be the point in the very center of the cube, equidistant to all faces.
by raigan2
Wed Nov 04, 2020 8:47 pm
Forum: Links, Papers, Libraries, Demos, Movies, Comparisons
Topic: recent PBD papers
Replies: 1
Views: 6796

recent PBD papers

I've been getting back into sim/pbd stuff after nearly a decade, and there have been a couple really interesting Position Based Dynamics papers released recently that I wanted to put on everyone's radar: This one is really mind-blowing -- tiny time steps with a single-solver-iteration per step behav...
by raigan2
Thu Jun 29, 2017 8:47 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Position Based Meshless Plasticity
Replies: 4
Views: 11946

Re: Position Based Meshless Plasticity

Have you tried the approach described in Muller "Meshless Deformations Based on Shape Matching"? AFAIK that's a popular way to implement meshless soft bodies with plastic deformations in a position-based simulation that might be worth a look. This paper from the same author has some useful...
by raigan2
Tue Apr 25, 2017 1:54 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Impulse-based vs force-based constraint solvers
Replies: 7
Views: 13724

Re: Impulse-based vs force-based constraint solvers

In my limited experience, some types of behaviour are awkward to model with position-based constraints -- for example, friction. I vaguely recall that motors were also a problem, but it's been so long I can't really remember the details! I definitely remember thinking "behaviours that are natur...
by raigan2
Mon Sep 14, 2015 6:30 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: continuous collision detection(point of collision;
Replies: 2
Views: 4446

Re: continuous collision detection(point of collision;

Erin Catto's GDC2013 presentation on "bilateral advancement" might be worth checking out: http://box2d.org/files/GDC2013/ErinCatto_GDC2013.zip

(he uses distance queries rather than SAT, but maybe the general idea is useful..)
by raigan2
Sun Aug 02, 2015 1:01 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Jacobsen & Verlet - embedding simplex in polytopes
Replies: 7
Views: 8045

Re: Jacobsen & Verlet - embedding simplex in polytopes

You're welcome! (We're Metanet Software http://www.metanetsoftware.com/blog/ ) We made a couple crappy vids using this solver, but then kind of got burnt out. I'm hoping to revisit it sometime though, it had a lot of potential IMO! https://www.youtube.com/watch?v=YHVyg2rDBy4 https://www.youtube.com/...
by raigan2
Fri Jul 31, 2015 12:40 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Jacobsen & Verlet - embedding simplex in polytopes
Replies: 7
Views: 8045

Re: Jacobsen & Verlet - embedding simplex in polytopes

Cheers! This stuff was such a headache to figure out that I'm glad to help someone avoid that as much as possible :) I still think that it's "geometry embedded in particles" (or really, "geometry embedded in frame derived from particle positions") and not the other way around, be...
by raigan2
Tue Jul 28, 2015 12:19 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Jacobsen & Verlet - embedding simplex in polytopes
Replies: 7
Views: 8045

Re: Jacobsen & Verlet - embedding simplex in polytopes

That's very interesting. You wouldn't happen to remember any of those approaches..? Just the stick-based one I described (and, we have a few other weird IK-based embeddings, where the collision geometry is a function of the length between two particles connected via min/max distance constraint). As...
by raigan2
Sun Jul 26, 2015 7:36 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Jacobsen & Verlet - embedding simplex in polytopes
Replies: 7
Views: 8045

Re: Jacobsen & Verlet - embedding simplex in polytopes

I've done this a couple different ways in 2d, I'm unfortunately really busy at work but I'll try to explain what I know and hopefully it gives you some ideas. (also it's been about 5 years..) In general you have some collision geometry which is embedded in a frame, so the geometry is a function of t...
by raigan2
Sat Nov 15, 2014 6:08 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Verlet collision by particle path ray.
Replies: 9
Views: 10633

Re: Verlet collision by particle path ray.

Do your particles have a radius/thickness? This would probably help make things behave a bit better. One thing I've done in the past to make particle collision a bit less fussy is to raycast using a thick ray (which has a radius smaller than the full size of the particle), and stop at the moment of ...
by raigan2
Mon Sep 29, 2014 12:17 am
Forum: Links, Papers, Libraries, Demos, Movies, Comparisons
Topic: Projective Dynamics
Replies: 3
Views: 11328

Re: Projective Dynamics

Cool, thanks for the heads-up!
by raigan2
Thu Sep 25, 2014 8:35 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Inequality Constraint in PBD
Replies: 4
Views: 5944

Re: Inequality Constraint in PBD

If your state is within the valid region: the constraint isn't violated, you don't have to do anything. If your state is outside the valid region: find the point on the surface of the valid region closest to the current state, this is your target state. So, for a min/max distance constraint: if(curr...
by raigan2
Thu Sep 25, 2014 8:29 am
Forum: Links, Papers, Libraries, Demos, Movies, Comparisons
Topic: Projective Dynamics
Replies: 3
Views: 11328

Projective Dynamics

Just came across this and thought it might be of interest:

"Projective Dynamics: Fusing Constraint Projections for Fast Simulation"
http://lgg.epfl.ch/~bouaziz/pdf/Project ... PH2014.pdf
https://www.youtube.com/watch?v=TkzmqAgcilU
by raigan2
Thu Sep 04, 2014 1:36 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Position based dynamics and collision constraints
Replies: 1
Views: 4713

Re: Position based dynamics and collision constraints

I think there are a few different ways to handle this. An approach I've used with a position-based solver is "speculative collisions": at the start of the frame, generate all pairs of potentially colliding features, and solve them speculatively (i.e inside the solver you check if there's p...