In article <396572FB.AC4D4BD3@nospamthanks.hotmail.com>, Pabs 
<pab### [at] nospamthankshotmailcom> wrote:

> Could work but maybe you could specify some different types of sampling -
> like the box method, point & bbox method, sphere & bbox method, random
> points in random directions et al.

That would be possible, but I don't know how useful it would be. I think 
the best coverage would result from taking a random point in the 
bounding box and firing the ray in a random direction...that seemed to 
produce the best coverage for the proximity pattern.


> Are U going to add propogation reactions like when a particle 
> interacts with a surface/other particle it creates new particles & 
> changes in some way.

I plan to implement things this way:
If a particle impacts a surface while traveling at a speed higher than a 
specified threshold, it will break into multiple particles smaller than 
the original(conserving mass and volume). Particle fission will also 
occur if the particle density in an area drops below a certain threshold.

Low-velocity impacts on a surface will take a different set of rules...I 
might add calculations based on proximity to the surface. The particles 
will cling to the surface, making it "get wet".

Particles will join together(fuse) if their velocities are close to 
being identical. This will be more likely if the particle density in the 
area is higher, and will not happen if it is below a certain threshold. 
This will help keep the simulation fairly efficient, so it doesn't get 
bogged down with a bunch of tiny particles.


> > 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...
> 
> What like ignoring particles so far away that the contribution is
> negligible.

That is already done, but the distance calculation itself takes 
time...which is why I am going to attempt to make a bounding structure.


> Another pattern could be based on the velocity & or direction of the
> particles.

Or even better, a single pattern that can do all of those...particle 
density, average speed, average temperature, average age...

-- 
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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