Rigid Body Dynamics Question

Darryl Barnhart · 2004-02-23T13:50:14

Ok I''ve been getting into rigid body dynamics and I''ve read the articles by Chris Hecker, and the intro by David Baraff. Both people do something very strange in there calculations. It''s when they are taking a force applied at some point r away from the center of mass of the body, and translating in into the overall translational force of the body. They simply state that the applied force is overall force with no alteration at all. I say that the applied force projected onto r is the overall force. My reasoning is that the energy contained within the force must either go into angular kinetic energy or linear kinetic energy, but not both. Thus to component of the appied force that is perpendicular to r would go into rotation (that''s why you use a cross product here), and the remaining applied force, which is necessaily perpendicular to r would go into tranlation (that''s why I say to use a projection). According to Hecker and Baraff, all the enegy going into linear kinetic energy, and some more somehow appears, which is impossible, and goes into angular kinetic energy. So who''s right me or Chris Hecker and David Baraff? Have I missed some crucial fact or something?

Math and Physics Programming

Started by DudeMiester February 20, 2004 04:43 PM

10 comments, last by DudeMiester 20 years, 2 months ago

Anonymous

February 23, 2004 09:09 AM

Of course you can use LCP for collisions:
http://isg.cs.tcd.ie/giangt/EGIrl2003.pdf

I use this method myself, and it works perfectly.

MrRowl

2,496

February 23, 2004 01:50 PM

quote:Original post by Anonymous Poster
Of course you can use LCP for collisions:
http://isg.cs.tcd.ie/giangt/EGIrl2003.pdf

I use this method myself, and it works perfectly.

Yup - ta for reminding me of that paper. Now I''ve got stuff working with the sequential approach I should try the other too...

For now I''m desperately trying to think where I got that nugget of misinformation that I reproduced without really thinking about it...!

Rigid Body Dynamics Question

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Rigid Body Dynamics Question

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