Chris Huff wrote:


> <ber### [at] inamecom> wrote:
>
> >       It could, but that would mean recomputing the cloth at each render which
> > would be very slow.
>
> What about cloth simulation *requires* this? It could easily be kept as
> a persistent object, like the particle_system patch, or have data stored
> in a temporary file, like radiosity or photon mapping.

Cloth is simulated over time - a static model is not.  If cloth were implemented in
POV, you would have to specify how much time you want to step the simulation before
doing the rendering.  Too little time means that the cloth hasn't finished falling
and covering the area.  Too much time and the cloth could have fallen right off your
surface.  If you were to create an animation with cloth, you would have to simulate
from the start of the cloth simulation to the proper point in the scene.  Unless you
have some way of rendering multiple scenes in POV without stopping, you'd have to
recalculate that each frame and it would take longer each time.

Having said all that, it's possible to write the cloth simulation as part of POV or
as a separate utility.  The problem with a separate utility is that you have to
re-implement all of the POV shapes in the utility.  Incidently, the cloth-surface
intersection calculations are the same ones used for ray-surface intersection
already implemented in POV, so all the existing shapes could be supported for the
cloth to drape over.

David Buck
dav### [at] simberoncom

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