"Chaps" <cha### [at] yahoocom> wrote in message
news:3c514dd3@news.povray.org...
> I do the same, but i need to change time step each time I change the
> "accuracy" of the mesh, and I don't like tries and error algorithm :o(.
>
> I've been driven to a site where there are some studies about cloth
> stability with large step calculus, but I did not succeed to get something
> out of this stuff yet.( http://www-2.cs.cmu.edu/~baraff/papers/).

Hi Chaps!

What a coincidence! I spent nearly all day yesterday to try to understand
that document. Actually I did understand most of it, but I got badly stuck
with the C(x) condition vector... I believe there must be some errors, or at
least it is not very well explained, because in the Stretch Forces section
(4.2), C(x) is defined as a 2-dimensional vector:

C(x) = a (|wu(x)| - bu , |wv(x)| - bv )

However, in the shear and bend forces section (4.3), C(x) is defined as

C(x) = a * wu(x)^T * wv(x)

Which, I believe it is 1-dimensional, that is, a scalar.

And then, in the Forces and Force Derivatives section (4.1) it says that the
force can be computed like this:

f_i = -k dC(x)/dx_i * C(x)

But f_i is a 3-dimensional vector, so I believe there must be an error
because there is no dimensional agreement. I may be wrong, but I'm stuck.

Did you have the same problem?

Fernando.

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