Matt Savard wrote:

> Has anyone done any work with implementing a particle system in POV? With
> all the cool features like blobs and interiors and such, I think this would
> be fantastic.

What a coincidence - I have recently come across a particle rendering system by
James Neill, who did a project in his 3rd year at Uni on this topic and I have
contacted him, asking for the possible inclusion of his code in POV-Ray and he
agreed, saying that he originally wanted to do it as part of POV but didn't
have the time (for the last 5 years).
So I am now trying to get hold of the work his project (see below) was based on

-Check it out at http://home.clara.net/renaissance59/projects/index.html
So far he has given me the following url to help me track them down
http://www.cs.man.ac.uk/aig/staff/alan/gallery/misc/index.html

Some improvements I suggested - oh hell the reply to my suggestions follows
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Alan & Pabs

Alan - I've cc'ed you on this mail, because I've had an enquiry from 'Pabs'
about integrating the ray tracing particle systems project I did under you
tutorship in 1995 (I think) with the POV ray tracer. I put my old project on
the web here http://home.clara.net/renaissance59/

Pabs last email follows : -

> In your report you mention two other projects by M. Kong [It was actually M.
Brooks] and
> someone else[this was Ryan Kelly] -
> where could I get these from - esp the particle generator & code

I think it was Ryan Kelly that did the particle modelling. Alan may have
more info.

http://www.cs.man.ac.uk/aig/staff/alan/gallery/misc/index.html

>
> Also do you have any record of how long the renderings of
> each of your test
> images took

I think it was around 30 seconds for a 400 x 300 image. But this was using
gcc under MSDOS on a 486-33. Will probably be faster now :). The refraction
images were the ones that took the longest, becuase what starts as one ray
of light effectively becomes lots more rays of lights depending on how many
particles it passes within the threshold distance.

> Couple of things I'd like to run by you
> -options to refract the ray away from a particle, to change
> the bend point
> and bend to the side as well - maybe create reflecting particles

Refracting the light away from the particle would be easy. At present a ray
that passes a particle is bent towards the center of the particles 'field of
effect' I think the weight of this effect was based on a cosine curve. I do
remember having divide by zero problems when a ray passed directly throught
the center of the particle :)

> -In pov maybe the scene could have induvidual particles
> entered by the scene
> author and other objects (spheres, boxes, etc) could be
> containers for
> pov-generated particles (using the above mentioned particle
> generator code)
> Any comments/ideas would appreciated

Good idea - you could model something like the Sun as just a set of particle
that can't leave a sphere (where the sphere is invisible). Stick a light
source on the middle of the sphere and hey presto you've got a Sun.

I think Ryan Kelly's project was modelling particles over time due to effect
of things like gravity. It would chuck out a file describing the particle
positions every second.

If modelling reality the particle generator will need the scene description
so that over time it models the particle positions and how they interact
with the environment described in the POV scene (ie, like the image of the
particles bouncing off the sphere)


Regards
James Neill
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Any way I'll keep this thread informed
Seeya
Pabs

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