Search found 19 matches

by nisse
Mon Mar 21, 2011 9:52 pm
Forum: Links, Papers, Libraries, Demos, Movies, Comparisons
Topic: Parallelizable conjugate gradient-based MLCP solver
Replies: 6
Views: 8579

Re: Parallelizable conjugate gradient-based MLCP solver

Thanks for sharing. That is really grand of you! I will read it. First reflection. I don't see any system with complementarity conditions among the test systems. What type of systems that imposes bounds on the multipliers or velocity have you considered? And are the results for that also just as pos...
by nisse
Mon Jan 03, 2011 7:03 am
Forum: Links, Papers, Libraries, Demos, Movies, Comparisons
Topic: Hybrid Multiresolution Wire
Replies: 0
Views: 3711

Hybrid Multiresolution Wire

We describe a method for the visual interactive simulation of wires contacting with rigid multibodies. The physical model used is a hybrid combining lumped elements and massless quasistatic representations. The latter is based on a kinematic constraint preserving the total length of the wire along a...
by nisse
Mon Jan 03, 2011 7:02 am
Forum: Links, Papers, Libraries, Demos, Movies, Comparisons
Topic: Constraint Fluids
Replies: 0
Views: 2920

Constraint Fluids

We present a fluid simulation method based on Smoothed Particle Hydrodynamics (SPH) in which incompressibility and boundary conditions are enforced using holonomic kinematic constraints on the density. This formulation enables systematic multiphysics integration in which interactions are modeled via...
by nisse
Mon Dec 27, 2010 8:36 pm
Forum: Links, Papers, Libraries, Demos, Movies, Comparisons
Topic: Release of AGX, and some new videos and stuff from Algoryx
Replies: 4
Views: 5825

Re: Release of AGX, and some new videos and stuff from Algor

You can find pre-prints here Constraint fluid: http://www.physics.umu.se/english/research/statistical-physics-and-networks/complex-mechanical-systems/fluids-and-solids/ Realtime hybrid wire: http://www.physics.umu.se/english/research/statistical-physics-and-networks/complex-mechanical-systems/realti...
by nisse
Wed Aug 11, 2010 8:24 am
Forum: Links, Papers, Libraries, Demos, Movies, Comparisons
Topic: New research on real-time deformable body dynamics (FEM).
Replies: 28
Views: 24768

Re: New research on real-time deformable body dynamics (FEM)

Nisse and XperienS: I only know to use CG to solve linear eqaution but don't know how to use it solve LCP, Could you refer me some Material how to use active set in CG method to solve LCP with unilateral contacts and box constraint like friction? I guess we are all looking for ways to do that. The ...
by nisse
Mon Aug 09, 2010 8:29 am
Forum: Links, Papers, Libraries, Demos, Movies, Comparisons
Topic: New research on real-time deformable body dynamics (FEM).
Replies: 28
Views: 24768

Re: New research on real-time deformable body dynamics (FEM)

Impressive work! Are you solving the contacts as unilateral contacts - with friction - using the CG solver as well? Do you have your own method for handling the active set in the LCP solve or do you use some standard method? That is the hardest part to parallelize as I understand the problem. Keep u...
by nisse
Mon Apr 05, 2010 5:24 pm
Forum: Career Opportunities
Topic: PhD Student Position
Replies: 0
Views: 5281

PhD Student Position

PhD Student Position in Computational Science and Engineering - Umeå University, Sweden. We are looking for an exceptional PhD student to join our interdisciplinary group focusing on modeling and numerical simulation of complex mechanical systems. This is a full-time position over a period of four y...
by nisse
Sat Mar 20, 2010 7:24 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Non elastic rope II
Replies: 4
Views: 5739

Re: Non elastic rope II

This is a well-known instability. Light elements under high tension vibrates at high frequency - like tuning a guitar string. When the vibrational frequency becomes close to or smaller than the time-step size these high-frequency modes may develop into instabilities. Increasing mass, element size an...
by nisse
Mon Mar 01, 2010 7:41 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Solids collision response theories [?]
Replies: 2
Views: 1216

Re: Solids collision response theories [?]

I recommend the book "Computational Granular Dynamics" by Pöschel and Schwager. As the titel reveals it is oriented towards compuational techniques and simulation and covers both explicit force methods (penalty methods based on physical deformation models - eg the Hertz model), impulse events and fr...
by nisse
Fri Nov 20, 2009 7:26 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Wake and sleep strategies
Replies: 5
Views: 1523

Re: Wake and sleep strategies

dellsmaith

You are kidding with me, right!? In that case I find it actually hilarious :lol: The relaxation process is indeed good for wake and sleep, especially for large mammals.

But if whas a serious tip, please provide me with the precise keywords...
by nisse
Thu Sep 24, 2009 11:48 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Finite Elements Method: are there proble,s with stability?
Replies: 57
Views: 24971

Re: Finite Elements Method: are there proble,s with stability?

FD, Have you (or anyone else) tried preconditioning of the iterative solver? That is, you warm-start the solver with lagrange multipliers that is the best estimation of the solution you can do a priori - instead of using the initial iteration solve. The estimation could be a direct solve of a subsys...
by nisse
Thu Sep 24, 2009 8:23 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Finite Elements Method: are there proble,s with stability?
Replies: 57
Views: 24971

Re: Finite Elements Method: are there proble,s with stability?

The "How to make new joints in ODE" http://ode.org/joints.pdf has some even more details on this as well. One thing that is not stressed enough in that text, I think, is that for the mapping of the spring stiffness and damping coefficients to CMF and ERP to hold relies critically on that the Jacobia...
by nisse
Tue Sep 15, 2009 9:49 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Finite Elements Method: are there proble,s with stability?
Replies: 57
Views: 24971

Re: Finite Elements Method: are there proble,s with stability?

...it makes the constraints soft and in my opinion this is not what people want (e.g. stretchy ragdolls).-Dirk Well, ideal is to be able to parametrize the joint stiffnes ranging from soft to indefinetly stiff AND use conventional material parameters for this (e.g. Young's modulus etc). In this thr...
by nisse
Sun Sep 13, 2009 11:31 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Finite Elements Method: are there proble,s with stability?
Replies: 57
Views: 24971

Re: Finite Elements Method: are there proble,s with stability?

It seems the use of iterative v.s. direct solver might explain the difference in stability. But I am not sure. I use iterative solver sometimes as well and don't recall any particular difficulties with stability in the stiff limit. The problem usually shows up as the material being overly elastic wh...
by nisse
Sun Sep 13, 2009 8:44 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Finite Elements Method: are there proble,s with stability?
Replies: 57
Views: 24971

Re: Finite Elements Method: are there proble,s with stability?

This paper has a few details on how DMM works, it might be worth checking out: http://www.cs.berkeley.edu/b-cam/Papers/Parker-2009-RTD/ Indeed, this is very good work. Very nice to see to see it working in a commercial game and that the physics is essential for the game play as well. I am intereste...