In article <396414C4.B17FD9F4@nospamthanks.hotmail.com>, Pabs 
<pab### [at] nospamthankshotmailcom> wrote:

> 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.

Hmm, that could work, though I would have to save the points for later 
use, kind of like a large number of point emitters...how should I take 
the samples, though? If I take them from the surface of a sphere toward 
the center of the bounding box, there will be a serious tendency for the 
center of the object unless it is hollow and fairly spherical. Maybe if 
I took them from the three sides of a box...along each coordinate axis, 
in other words.


> 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.

This actually existed in the first versions of my patch, in fact, it was 
*the* first version of my patch, but I have removed it because it was 
too difficult to maintain while the rest of the patch was changing so 
rapidly...I do plan on replacing it, however.
Hmm, particle density...I hadn't thought of that. I will need to write a 
function to compute this for particle fission/fusion anyway, so might as 
well include it...
BTW, one other problem with the particle_system pattern was that it was 
slow, since all the particles had to be calculated. I plan on adding a 
bounding structure based on recursively subdividing boxes(I think it is 
called an octree...) or planes(I have no idea what this is called) to 
speed up inter-particle force calculations, so that should really speed 
up the patterns...

-- 
Christopher James Huff - Personal e-mail: chr### [at] maccom
TAG(Technical Assistance Group) e-mail: chr### [at] tagpovrayorg
Personal Web page: http://homepage.mac.com/chrishuff/
TAG Web page: http://tag.povray.org/

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