[ODE] How do I code my own constraints ?

Gazza gazza at shaw.ca
Fri Nov 1 17:10:02 2002


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Hi,

I'm trying to understand how to compute the constraints matrix for a particular constraint.

I'm of the understanding that a 'contact' constraint would remove a DOF along the contact normal, thus requiring 1 value.  When solved, the force/impulse is applied along the normal.  For a ball joint, 3 DOF's are removed - x,y,z translations,  and for a hinge, 5 DOF's are removed - x,y,z translation and say x,y rotation.  Am I correct in these assumptions ?

What I don't understand (or can find any documentation/papers on) is how the value(s) are computed for the A(n*n) matrix and b(n*1) for each constraint, which tell the system to remove these DOF's.

Any help given is most appreciated.

Thanks in advance.
  Gazza

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<DIV><FONT face=Arial size=2>Hi,</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT>&nbsp;</DIV>
<DIV><FONT face=Arial size=2>I'm trying to understand how to compute the 
constraints matrix for a particular constraint.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT>&nbsp;</DIV>
<DIV><FONT face=Arial size=2>I'm of the understanding that a 'contact' 
constraint would remove a DOF along the contact normal, thus requiring 1 
value.&nbsp; When solved, the force/impulse is applied along the normal.&nbsp; 
For a ball joint, 3 DOF's are removed - x,y,z translations,&nbsp; and 
f</FONT><FONT face=Arial size=2>or a hinge, 5 DOF's are removed - x,y,z 
translation and say x,y rotation.&nbsp; Am I correct in these assumptions 
?</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT>&nbsp;</DIV>
<DIV><FONT face=Arial size=2>What I don't understand (or can find any 
documentation/papers on) is how the value(s) are computed for the A(n*n) matrix 
and b(n*1) for each constraint, which tell the system to remove these 
DOF's.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT>&nbsp;</DIV>
<DIV><FONT face=Arial size=2>Any help given is most appreciated.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT>&nbsp;</DIV>
<DIV><FONT face=Arial size=2>Thanks in advance.</FONT></DIV>
<DIV><FONT face=Arial size=2>&nbsp; Gazza</FONT></DIV></BODY></HTML>

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