[ODE] Constraint theorizing

Henri Hakl henri at cs.sun.ac.za
Sun Feb 23 04:58:01 2003


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Hi :)

...this goes out to all those that actually know/understand the theory =
behind constraint-based physics (not me).

I was just wondering, if there is a theoretical reason why all the =
physics are computed into one giant contraint matrix.

Consider the following simple generic case:

The floor, and 2 boxes falling onto it. The boxes are quite far apart =
and won't even come remotely close to touching each other.

Instead of solving the constraints in one (for argument's sake) 20x20 =
matrix, why not use two 10x10 matrices that handle the boxes seperately?

Mathematically it is much faster to solve for two 10x10 matrices, rather =
then one 20x20 matrix. Is it that difficult to determine which objects =
are sufficiently independent to warrant a seperate constraint matrix? I =
think not.

Anybody willing to shoot this idea down?
  Henri


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<DIV><FONT face=3DArial size=3D2>Hi :)</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>...this goes out to all those that =
actually=20
know/understand the theory behind constraint-based physics (not=20
me).</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>I was just wondering, if there is a =
theoretical=20
reason why all the physics are computed into one giant contraint=20
matrix.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>Consider the following simple generic=20
case:</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>The floor, and 2 boxes falling onto it. =
The boxes=20
are quite far apart and won't even come remotely close to touching each=20
other.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>Instead of solving the constraints in =
one (for=20
argument's sake) 20x20 matrix, why not use two 10x10 matrices that =
handle the=20
boxes seperately?</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>Mathematically it is much faster to =
solve for two=20
10x10&nbsp;matrices, rather then one 20x20 matrix. Is it that difficult =
to=20
determine which objects are sufficiently independent to warrant a =
seperate=20
constraint matrix? I think not.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>Anybody willing to shoot this idea=20
down?</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>&nbsp; Henri</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV></BODY></HTML>

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