Search found 135 matches

by Antonio Martini
Sat May 31, 2008 2:15 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: A new PGS solver
Replies: 19
Views: 7090

Re: A new PGS solver

1 - Assume both constraints are active and solve the 2-by-2 equality problem. If both contact forces are positive then we are done. 2 - Assume contact 1 is active and contact 2 is inactive. Solve for contact force 1. If contact force 1 is positive and contact velocity 2 is non-negative then we are ...
by Antonio Martini
Sat May 17, 2008 1:07 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Decomposition of bodies intro tetrahedrons
Replies: 3
Views: 1424

Re: Decomposition of bodies intro tetrahedrons

In many cases, thin shell is enough to simulate deformable bodies, check out http://www.diku.dk/forskning/image/kenny/dsagm04.pdf . in a discrete time simulation that includes collision detection and response, this approach seems to lead to a less robust solution as nodes may end up in the empty sp...
by Antonio Martini
Sat May 17, 2008 12:52 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Collision detection for soft bodies
Replies: 2
Views: 2011

Re: Collision detection for soft bodies

For closed mesh, I'm experimenting with deformable signed distance fields, which, provided an well tessellated mesh, guaranty an O(1) collision query, and are very robust. distance fields suffer from various artifacts, see for example fig.1 of: http://www.beosil.com/download/PenetrationDepth_VMV04....
by Antonio Martini
Sun May 04, 2008 5:54 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Who invented Islands?
Replies: 3
Views: 4545

Re: Who invented Islands?

Hi guys, looking for the paper that introduced the concept of islands or explains them in enough depth to act as a reference. so far I haven't had much joy :/ look for 'disconnected components' in graph theory: see for example the 'Connected components' section of: http://www.cs.cornell.edu/Courses...
by Antonio Martini
Sat Apr 26, 2008 2:17 pm
Forum: Links, Papers, Libraries, Demos, Movies, Comparisons
Topic: new Euphoria video
Replies: 0
Views: 2604

new Euphoria video

http://www.naturalmotion.com/euphoria.htm#video http://www.shacknews.com/laryn.x?story=52403 it would be nice to see more videos of in game real case scenarios and so in a more interactive context. I am curious to see how it looks in GTAIV. EDIT: nice backbreaker gameplay video here: http://www.shac...
by Antonio Martini
Thu Apr 17, 2008 11:07 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: A new PGS solver
Replies: 19
Views: 7090

Re: A new PGS solver

Well, usually we solver just a single row a time, so solving say 6 rows at a time (6x6 blocks) would be an improvement. Blockwise solving would be easily implemented in both SI and PGS. i have not read the paper, however hasn't block solving already been used for a very long time now? block solvers...
by Antonio Martini
Tue Apr 15, 2008 4:48 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Friction and LCP
Replies: 23
Views: 8004

Re: Friction and LCP

About credit of PGS, I view it like this: PGS is there for a long time, Moreau or anyone who applied PGS to handle unileteral constraints should get a credit for applying (the right) tool to this particular problem. I personally think he made a good contribution (if he's the first) to game physics....
by Antonio Martini
Tue Apr 15, 2008 4:23 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: A new PGS solver
Replies: 19
Views: 7090

Re: A new PGS solver

[This is a repost from ODE list] Hi. I stumble across this paper: "An Algorithm for the Approximate and Fast Solution of Linear Complementarity Problems" http://www-unix.mcs.anl.gov/~leyffer/listn/slides-07/morales.pdf It has a description of a new PGS that should work directly with ODE and (should...
by Antonio Martini
Sat Apr 12, 2008 6:24 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Friction and LCP
Replies: 23
Views: 8004

Re: Friction and LCP

Erin's implementation of SI is equivalent to PGS. SI like described by Mirtich or Guendelman are not. Actually the differences only holds for inequality constraints when you need to clamp. All SI implementations are equivalent to PGS for equality constraints. Erin was indeed the first to publish a ...
by Antonio Martini
Sat Apr 12, 2008 5:54 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Friction and LCP
Replies: 23
Views: 8004

Re: Friction and LCP

A crucial ingredient to this is clamping of accumulated impulses, which I had not seen published anywhere. yes this is what i thought that it was new when i read your paper/presentation for the first time. I dont remember the details of the Claude's paper, can anybody point out in which paper and w...
by Antonio Martini
Tue Apr 01, 2008 2:43 pm
Forum: Links, Papers, Libraries, Demos, Movies, Comparisons
Topic: OctaveEngine Casual
Replies: 0
Views: 2372

OctaveEngine Casual

http://www.developmag.com/news/29556/Oc ... o-launched

a nice demo can be downloaded by following the links.

Antonio
by Antonio Martini
Mon Mar 24, 2008 5:05 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Soft bodies early preview
Replies: 41
Views: 25128

Re: Soft bodies early preview

just to recap as here i get the feeling that far too many methods have been discussed together. For volumes you are basically using shape matching as in: http://www.matthiasmueller.info/publications/MeshlessDeformations_SIG05.pdf where for now you only have one cluster of vertices right? if so in it...
by Antonio Martini
Sun Mar 23, 2008 4:39 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Soft bodies early preview
Replies: 41
Views: 25128

Re: Soft bodies early preview

it happens but some methods seem numerically more robust and can recover gracefully I did test it, each application of gradient correction does in fact recover from sign inversion through (graceful:)) rotations, that could be a problem for one element, but usually more than one tetrahedron share a ...
by Antonio Martini
Sat Mar 22, 2008 2:29 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Soft bodies early preview
Replies: 41
Views: 25128

Re: Soft bodies early preview

>Thinking about it, the M matrix is symmetric , there must exist a better (non iterative) way to extract a polar decomposition. if polar >decomposition ever become a bottleneck, i should get back to it. Never mind, that's wrong. Nat. from the back of my mind the non iterative approach aside from QR...
by Antonio Martini
Sat Mar 22, 2008 1:42 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Soft bodies early preview
Replies: 41
Views: 25128

Re: Soft bodies early preview

Nathanael wrote: But even using gradient directions, volume inversion do happen
it happens but some methods seem numerically more robust and can recover gracefully, see section 3.4 of:

http://www.matthiasmueller.info/publica ... GI2004.pdf

cheers,
Antonio