Search found 211 matches

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: 6533

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 reference...
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: 6662

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 naturally ...
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: 3060

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: 5359

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: 5359

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, because the particles ...
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: 5359

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: 5359

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: 7375

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: 6381

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: 4152

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: 6381

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: 3417

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 penetration...
by raigan2
Tue Aug 12, 2014 4:39 pm
Forum: Links, Papers, Libraries, Demos, Movies, Comparisons
Topic: FastLSM soft body physics (source code available) original
Replies: 3
Views: 9131

Re: FastLSM soft body physics (source code available) origin

If you want to try integrating it with other types of simulation (cloth, etc) you might want to check out this paper: http://blog.mmacklin.com/flex/
by raigan2
Sun Jul 29, 2012 2:29 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Impulse-based fluid?
Replies: 2
Views: 3544

Re: Impulse-based fluid?

Awesome, thanks! Hadn't seen that... Lacoursiere is prolific! :)
by raigan2
Thu Jul 26, 2012 6:07 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Impulse-based fluid?
Replies: 2
Views: 3544

Impulse-based fluid?

I just came across this blog post about the fluid in Sprinkle: http://tuxedolabs.blogspot.ca/2011/11/sprinkle-behind-scenes.html Does anyone have any tips on how one might formulate the attractive/repulsive inter-particle forces in a fluid as position and/or velocity constraints, as hinted at in tha...