Search found 235 matches

by bone
Fri Sep 08, 2017 1:34 pm
Forum: Links, Papers, Libraries, Demos, Movies, Comparisons
Topic: Why all physics engines differ each other
Replies: 2
Views: 3277

Re: Why all physics engines differ each other

^^^ What he said. ^^^

Nice concise explanation.
by bone
Thu Sep 07, 2017 2:28 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Algorithm help / Connecting Centroids
Replies: 11
Views: 5704

Re: Algorithm help / Connecting Centroids

Looks like a fascinating project! We brushed on this earlier, but how does the transition from 2-D to 3-D affect those intersections (the red and black dots from the original post)? I can't immediately picture if there would still be only two classifications of intersections. Anyway, wish I could he...
by bone
Thu Aug 31, 2017 2:43 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Algorithm help / Connecting Centroids
Replies: 11
Views: 5704

Re: Algorithm help / Connecting Centroids

Ahh, I misunderstood one sentence in your first post. The previous algorithm could be expanded a bit: for every red dot for every red dot if they share exactly two circles (if they're actually the same red dot, they'll "share" three circles) connect them for every black dot if they share two circles...
by bone
Mon Aug 28, 2017 6:46 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Algorithm help / Connecting Centroids
Replies: 11
Views: 5704

Re: Algorithm help / Connecting Centroids

Well, in a simple brute force algorithm form, it's just going to be: for every red dot for every black dot if they share two circles connect them The caveats are: 1) That's inefficient, but that's part of why I mentioned what information you have, because it can be made far more efficient, and 2) Yo...
by bone
Mon Aug 28, 2017 1:50 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Algorithm help / Connecting Centroids
Replies: 11
Views: 5704

Re: Algorithm help / Connecting Centroids

I don't know what information you have available, but it appears that there is a connection between black and red dots any time they share two circles.
by bone
Tue Apr 25, 2017 1:40 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Impulse-based vs force-based constraint solvers
Replies: 7
Views: 4377

Re: Impulse-based vs force-based constraint solvers

And (naive question) if using impulses is better than using forces, why isn't using positions better than impulses? If you look at the literature on the relatively new Position Based Dynamics (PBD) technology, you'll find that it indeed does have some advantages (like stability). But it's usually e...
by bone
Tue Apr 11, 2017 1:51 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Continuous GJK
Replies: 7
Views: 4290

Re: Continuous GJK

I'm not enough of a mathematician to figure out what is meant by Dirk there, but in practice it is incredibly difficult to get accurate CCD for the 3D edge-edge case, even if you assume the 4 vertices are linearly moving through space. The normal you speak of often twists around in space between tim...
by bone
Fri Jan 06, 2017 5:35 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Trying to get a rough idea how many particles I can simulate
Replies: 2
Views: 2511

Re: Trying to get a rough idea how many particles I can simu

My opinion is that you could only achieve 100x speedup if your algorithm could work on the GPU. But you mention "if" conditions and unique data which is going to make a GPU solution not only difficult (or impossible), but much slower than many types of GPU-based particle systems. Now could you achie...
by bone
Mon Aug 29, 2016 3:14 pm
Forum: Links, Papers, Libraries, Demos, Movies, Comparisons
Topic: New physics library - PositionBasedDynamics
Replies: 6
Views: 8242

Re: New physics library - PositionBasedDynamics

I think it's an interesting question whether you can approach engineering-level accuracy given the same amount of computing power. One could just as well run PBD on the GPU (there are loads of parallelization possibilities), so the question is really what is your desired accuracy/speed tradeoff. If ...
by bone
Wed Aug 24, 2016 4:03 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: How to compute Lateral Friction Direction ?
Replies: 1
Views: 2309

Re: How to compute Lateral Friction Direction ?

Because friction is modeled as two semi-independent constraints (to model the 2 degrees of freedom on a 2-D surface), it's not really being modeled as a friction circle. More like a friction square or friction diamond. Because of this, you can get artifacts where the overall friction force is not qu...
by bone
Thu Jul 14, 2016 1:40 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Motor Control for Physics-Based Character Movement
Replies: 6
Views: 6305

Re: Motor Control for Physics-Based Character Movement

OK, fair enough. I'm not familiar with controlling robot motors, but don't they eventually need to be given power to apply some goal torque or something? Or is it just some PID control on a goal location/angle? If so, could you simulate such a PID yourself?
by bone
Wed Jul 13, 2016 5:19 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Motor Control for Physics-Based Character Movement
Replies: 6
Views: 6305

Re: Motor Control for Physics-Based Character Movement

Isn't this what inverse kinematics is for? I believe that's what is used for robot motion planning, and that's essentially what you're doing (except your "robot" is purely virtual).
by bone
Fri Mar 25, 2016 2:38 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Implementing hinge constraint
Replies: 11
Views: 7504

Re: Implementing hinge constraint

Congrats! And yes, I have also encountered some of my own fundamental math code with a mistake. Usually it was either never used before, or just had a marginal impact on the end result. Anyway, your hinge constraint sounds robust. Can it even handle rotations more than 180 degrees (like it is being ...
by bone
Wed Mar 09, 2016 2:25 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Implementing hinge constraint
Replies: 11
Views: 7504

Re: Implementing hinge constraint

Ahh, now I see where you're coming from. Well I'm afraid my math isn't good enough to help you. Good luck!
by bone
Tue Mar 08, 2016 7:50 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Implementing hinge constraint
Replies: 11
Views: 7504

Re: Implementing hinge constraint

I have a fully working constraint model and that's what I have for the Jacobian for a hinge. I don't know if quaternions would make any of my calculations easier, but I don't use any. It just seems they need to be converted to a matrix so often that they are more trouble than they're worth. Anyway, ...