Re: [Algorithms] Simulating Clay Modeling

[Bill B. <wb...@gm...>]

On Sat, Oct 18, 2008 at 7:54 AM, Tom Forsyth
<tom...@ee...> wrote:
> For FE stuff, I've had a lot of success modeling things like water as a "not
> very compressible" substance. So individual volumes of the substance can
> increase in density, but they react by pushing that mass very hard into
> adjacent volumes. The ratio I used (just from experimentation) was that a 1%
> increase in mass would cause a doubling of pressure. And like most FE
> systems, a delta of pressure between two adjacent elements caused mass to
> flow between them proportional to that pressure. This is still a linear
> enough response to allow even pretty hacky FE methods to work without any
> obvious instability (mine was certainly hacky!) while preserving the
> external appearance of true incompressibility.
>

That reminds me of something else I meant to mention.  There was a GD
magazine article -- back around 2000 I think -- that presented an
iterative technique like that.   (Maybe you wrote it?)  I think such
methods work pretty well for "local incompressibility".  So it could
be good for getting the effect of what happens when you push your
thumb into the clay.  But when you want to bend the whole shape
globally, it's not so much use.   So I think a combo of high
plasticity FEM + local iterative adjustment could be a good way to do
it.   A couple guys in my lab were working on a combo idea like this
back around 2000.  That's how I learned about the GD mag article.
They gave up on it eventually.  I don't think it was for any
insurmountable technical reasons though.

--bb