Search found 235 matches

by bone
Mon Dec 29, 2014 3:59 pm
Forum: General Bullet Physics Support and Feedback
Topic: multiple independent simulations.
Replies: 1
Views: 2947

Re: multiple independent simulations.

This section of the forum is for generic physics development, not Bullet-specific. If you haven't already, please post this question in the other section of the forum with regards to Bullet users.
by bone
Thu Oct 02, 2014 3:41 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Any smart ideas on contact resolution priorities?
Replies: 8
Views: 6688

Re: Any smart ideas on contact resolution priorities?

I'm pretty sure they mean to iterate over all of the sorted constraints in one loop.
by bone
Thu Sep 04, 2014 6:18 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: The difference between two constraint method
Replies: 3
Views: 3842

Re: The difference between two constraint method

Yes, that can have a significant effect in some cases, for example when stacking boxes. Various people have tried various orders with varying success. As a start, you might search for 'shock propagation' which I think was originally proposed by Guendelman.
by bone
Thu Sep 04, 2014 4:38 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: The difference between two constraint method
Replies: 3
Views: 3842

Re: The difference between two constraint method

I think you've highlighted the main advantage of direct solving. One downside, however, is that it is not simple to directly solve certain types of constraints, in particular collision and friction with their limits. So you need an MLCP solver. If this has ever been combined with a sparse matrix sol...
by bone
Wed Aug 27, 2014 8:47 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: How many iteration should be used for collision detection
Replies: 2
Views: 2879

Re: How many iteration should be used for collision detectio

Iterative solving is one way to handle multiple constraints that are not independent of each other. It's not clear why it is "obvious" to you that some kinds of collision constraints do not need to be iteratively solved. If it is the only constraint that needs to be solved, or it is completely indep...
by bone
Wed Aug 20, 2014 6:21 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Position-based Elastic Rod
Replies: 10
Views: 13386

Re: Position-based Elastic Rod

I think a lot of people are still checking this forum, but few are posting new questions.
by bone
Thu Jul 03, 2014 9:49 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Numerical Method
Replies: 2
Views: 3346

Re: Numerical Method

The ODEs are mildly simplified - rotation ignores the gyroscopic/Coreolis effect (whatever it's called). The numerical method is Symplectic Euler. This could be a big discussion, but based on the number of people who have tried different integration schemes, it's likely a waste of your time to try i...
by bone
Thu Apr 17, 2014 6:12 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: GJK/EPA and hollow shapes
Replies: 2
Views: 4366

Re: GJK/EPA and hollow shapes

Wouldn't hollow be the same case as concave? In which case, EPA/GJK aren't really suited to the task.
by bone
Mon Mar 24, 2014 4:39 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Collision & contacts <=?=> LCP
Replies: 6
Views: 5868

Re: Collision & contacts <=?=> LCP

Box2D is the first link in this thread, but the whole thread has some good resources to look at:

http://www.bulletphysics.org/Bullet/php ... p?f=6&t=63
by bone
Mon Mar 24, 2014 4:37 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Collision & contacts <=?=> LCP
Replies: 6
Views: 5868

Re: Collision & contacts <=?=> LCP

A lot of people seem to learn from Box2D by extending it into 3D.
by bone
Mon Mar 17, 2014 6:01 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Collision & contacts <=?=> LCP
Replies: 6
Views: 5868

Re: Collision & contacts <=?=> LCP

If you want to solve for contacts, you need to solve an MLCP (mixed linear complementarity problem).
by bone
Mon Feb 03, 2014 10:22 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Looking for research topics in areas of realtime physics
Replies: 10
Views: 10036

Re: Looking for research topics in areas of realtime physics

My work is more engineering-related, where double-precision is more common. Thanks for the additional info and pointers about this issue, though. Your example mass ratio is much more extreme than anything I use in practice. Originally I thought you were just complaining about the limit of most game ...
by bone
Mon Feb 03, 2014 6:46 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Looking for research topics in areas of realtime physics
Replies: 10
Views: 10036

Re: Looking for research topics in areas of realtime physics

As a motivating example, imagine a mass of 1e5 kg resting on top of a mass of 1e-5 kg resting on top of the floor. What's the force that the smaller body has to deliver to the larger body to keep it from falling down? Basically gravity * 1e5. And then, by Newton's third law, what's the force that t...
by bone
Fri Jan 31, 2014 3:49 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Looking for research topics in areas of realtime physics
Replies: 10
Views: 10036

Re: Looking for research topics in areas of realtime physics

A good way of handling collision response between bodies with vastly different mass ratios would be a reasonable project. It's not that it's an open problem so much as it's an unexplored problem. The onus is usually on the users to make the system less extreme by tweaking the masses. See, eg, this ...
by bone
Thu Jan 30, 2014 4:25 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Rigid body box stacking
Replies: 32
Views: 22273

Re: Rigid body box stacking

In my own simulation this style is very stable, but I have seen Erwin on these forums state that if an object slides quickly along a plane one of the friction axes can converge before the other causing an arced path of travel. I haven't noticed this artifact myself though. Like Dirk and Erwin, I've...