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# baraff - fast contact force

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hi - quick question about this paper - "Fast contact force computation for non-penetrating rigid bodies" - I can''t remember the link, but if you can answer this question you will probably have it anyway. I''m wondering if anyone can help me figure out how you set up the A matrix that is referred to early on in the equation a = Af + b (actually it''s the first numered equation in the paper!). The paper states that the matrix reflects the "masses and contact geometries of the bodies", proceeds to explain how to solve the equation but I can''t see an example of what the matrix looks like. I guess it''s got something to do with the p(i) points mentioned, and i know its symmetric etc....but that''s it. if anyone can help, please do! thanks!

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There is source code for calculating it in the course notes on his homepage.
http://www-2.cs.cmu.edu/~baraff/pbm/pbm.html

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You might also want to look at this
http://www.dh.aist.go.jp/~kawachi/isatp97/isatp97kawachi.pdf

This paper explains with a little more detail what Baraff is doing. Read section 2.2, i believe equation 10 is what you are asking about.

Its been a while since i''ve read the paper you are talking about...so I could be getting it confused with something else.

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thanks guys! just what i needed!

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Baraff''s site confuses me. There seem to be at least two documents on each topic, I''m getting confused which ones I''ve read! Is it the ''95 or ''97 things you''re all looking at?

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