Chris Huff wrote:

> In article <3962B4A1.A300F52D@nospamthanks.hotmail.com>, Pabs
> <pab### [at] nospamthankshotmailcom> wrote:
>
> > How about an object emitter where particles are emitted in the
> > direction of the surface normal and a speed specified by a
> > pattern/function.  The emmission points on the surface could be
> > sampled by tracing rays from a point & or direction toward that
> > object- kind of like how photons are done.
>
> I have been wondering about this...I just haven't thought of a good way
> of implementing it. It should be quite possible by specifying a point to
> sample surface positions from, as you suggest...but that would only
> cover part of the object. I could shoot at the center of the object's
> bounding box from random points on the surface of a sphere around
> it...but that would only give an even emission distribution for
> spherical objects, and parts of the object could be "hidden" from the
> particles by other parts. Would anyone notice?

It probably wouldn't be noticed unless someone used a noise3d isosurface as
the emitter.
BUT...
You could get _all_ intersections with each sampling ray - so that if you
hit a surface you keep tracing the _same_ ray until no more surfaces are hit
and therefore no parts of the object could be "hidden" from the particles by
other parts of the object.

Also what about a pattern that is the average particle density (or particle
collision density with the object whose pattern is being determined) in the
vicinity of the intersection point.  The particle(collision) density would
be the # of particles/collision points per unit space in the vicinity of the
intersection point or the addition of blob fields around all the
particles/collision points.
This could be used to visualize the drag on an airplane or fluid density or
other stuff.

Bye
Pabs

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