Comments on: Constrained Dynamics 2: Joints and Global Constraints http://blog.generalrelativity.org/actionscript-30/constrained-dynamics-2-joints-and-global-constraints/ Game-Oriented Development Fri, 06 Jan 2012 17:44:08 -0800 hourly 1 http://wordpress.org/?v=3.0.2 By: generalrelativity » Constrained Dynamics 1: Particle Constrained to Curve http://blog.generalrelativity.org/actionscript-30/constrained-dynamics-2-joints-and-global-constraints/#comment-170040 generalrelativity » Constrained Dynamics 1: Particle Constrained to Curve Fri, 13 May 2011 15:38:30 +0000 http://blog.generalrelativity.org/?p=219#comment-170040 [...] onto part 2, where we cover joints and global constraints. Categories: ActionScript 3.0, Mathematics, [...] [...] onto part 2, where we cover joints and global constraints. Categories: ActionScript 3.0, Mathematics, [...]

]]> By: drew http://blog.generalrelativity.org/actionscript-30/constrained-dynamics-2-joints-and-global-constraints/#comment-156242 drew Wed, 28 Jul 2010 13:47:58 +0000 http://blog.generalrelativity.org/?p=219#comment-156242 <a href="#comment-156220" rel="nofollow">@Philip</a> If you have zeroes on the diagonal, you're doing something incorrectly. Shoot me an email (drew at generalrelativity dot org) with the constraint equation and code and we'll figure out what's going on. @Philip
If you have zeroes on the diagonal, you’re doing something incorrectly. Shoot me an email (drew at generalrelativity dot org) with the constraint equation and code and we’ll figure out what’s going on.

]]> By: Philip http://blog.generalrelativity.org/actionscript-30/constrained-dynamics-2-joints-and-global-constraints/#comment-156220 Philip Wed, 28 Jul 2010 06:45:57 +0000 http://blog.generalrelativity.org/?p=219#comment-156220 Sorry to bother you again, the reason I asked you about the method you use to solve linear system is because when I tried to implement constraints I found myself with a system matrix with some zeros on the diagonal and, given I use Gauss-Jordan to solve it, the solution goes to infinity. Maybe I missed something in your article, but if I have 2 independent bodies and I try to apply a constraint to the second one (b2.index > b1.index): I have JWJt matrix that has 3 zeros on the first 3 diagonal values and then the body 2 constraint gradients (if I'm not wrong). Any help? Thank you. Sorry to bother you again,

the reason I asked you about the method you use to solve linear system is because when I tried to implement constraints I found myself with a system matrix with some zeros on the diagonal and, given I use Gauss-Jordan to solve it, the solution goes to infinity.
Maybe I missed something in your article, but if I have 2 independent bodies and I try to apply a constraint to the second one (b2.index > b1.index): I have JWJt matrix that has 3 zeros on the first 3 diagonal values and then the body 2 constraint gradients (if I’m not wrong).

Any help? Thank you.

]]> By: drew http://blog.generalrelativity.org/actionscript-30/constrained-dynamics-2-joints-and-global-constraints/#comment-156076 drew Mon, 26 Jul 2010 04:33:13 +0000 http://blog.generalrelativity.org/?p=219#comment-156076 Thanks for the links, David. Thanks for the links, David.

]]> By: drew http://blog.generalrelativity.org/actionscript-30/constrained-dynamics-2-joints-and-global-constraints/#comment-156075 drew Mon, 26 Jul 2010 04:14:49 +0000 http://blog.generalrelativity.org/?p=219#comment-156075 <blockquote cite="#commentbody-156024"> <strong><a href="#comment-156024" rel="nofollow">Philip</a> :</strong> <p>What method do you use to solve the linear system?</p> </blockquote> I use LU decomposition.

Philip :

What method do you use to solve the linear system?

I use LU decomposition.

]]> By: Philip http://blog.generalrelativity.org/actionscript-30/constrained-dynamics-2-joints-and-global-constraints/#comment-156024 Philip Sun, 25 Jul 2010 10:38:08 +0000 http://blog.generalrelativity.org/?p=219#comment-156024 Great article. What method do you use to solve the linear system? Great article.
What method do you use to solve the linear system?

]]> By: David http://blog.generalrelativity.org/actionscript-30/constrained-dynamics-2-joints-and-global-constraints/#comment-156012 David Sun, 25 Jul 2010 08:06:13 +0000 http://blog.generalrelativity.org/?p=219#comment-156012 <a href="#comment-154291" rel="nofollow">@drew</a> A couple days ago I noticed that the Bullet Physics Library website has a mirror of Erin's paper and the accompanying slides from a GDC presentation. I figured I'd post the links here in case anyone is interested. Paper: http://www.bulletphysics.com/ftp/pub/test/index.php?dir=physics/papers/&file=IterativeDynamics.pdf Slides: http://www.bulletphysics.com/ftp/pub/test/index.php?dir=physics/papers/&file=IterativeDynamicsSlides.pdf The Bullet site mirrors quite a few other papers as well. You can find them all at http://www.bulletphysics.com/ftp/pub/test/index.php?dir=physics/papers/ @drew
A couple days ago I noticed that the Bullet Physics Library website has a mirror of Erin’s paper and the accompanying slides from a GDC presentation. I figured I’d post the links here in case anyone is interested.

Paper: http://www.bulletphysics.com/ftp/pub/test/index.php?dir=physics/papers/&file=IterativeDynamics.pdf
Slides: http://www.bulletphysics.com/ftp/pub/test/index.php?dir=physics/papers/&file=IterativeDynamicsSlides.pdf

The Bullet site mirrors quite a few other papers as well. You can find them all at http://www.bulletphysics.com/ftp/pub/test/index.php?dir=physics/papers/

]]> By: drew http://blog.generalrelativity.org/actionscript-30/constrained-dynamics-2-joints-and-global-constraints/#comment-154291 drew Fri, 25 Jun 2010 23:37:28 +0000 http://blog.generalrelativity.org/?p=219#comment-154291 Thanks for the catch, I've updated the post. Thanks for the catch, I’ve updated the post.

]]> By: David http://blog.generalrelativity.org/actionscript-30/constrained-dynamics-2-joints-and-global-constraints/#comment-154288 David Fri, 25 Jun 2010 19:42:59 +0000 http://blog.generalrelativity.org/?p=219#comment-154288 Erin Catto took down the gyphysics.com website (it redirects to box2d.org now), but you can still access the Iterative Dynamics paper here: http://web.archive.org/web/20060621005754/http://www.gphysics.com/files/IterativeDynamics.pdf Erin Catto took down the gyphysics.com website (it redirects to box2d.org now), but you can still access the Iterative Dynamics paper here:
http://web.archive.org/web/20060621005754/http://www.gphysics.com/files/IterativeDynamics.pdf

]]> By: Niall http://blog.generalrelativity.org/actionscript-30/constrained-dynamics-2-joints-and-global-constraints/#comment-154014 Niall Fri, 18 Jun 2010 00:20:28 +0000 http://blog.generalrelativity.org/?p=219#comment-154014 Have you disappeared again? Have you disappeared again?

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