Hi all!

Yesterday while rendering my scene with 4000 blobs I got
an idea to a *usefull* object in povray and some of the
algorithms for it. What if I greate a particle object
relying on something related to the Noise function already
existing. What I think is this:

1]  The noise function associates a semirandom continuous
    value between 0 and 1 for every point in a 3D space. Let
    all values over a given threshold (0.8 maybe) be "inside"
    an object and all other points outside.

2]  Since the Noise function is linear between a given set of
    lattice points I can find the intersection of a ray with
    the objects by solving a linear intersection for every
    3D cube between the lattice points which my ray passes. 

3]  The gradient in such a point is also computable.

4]  Turbulence *might* (I not sure) be added with some "sampling"
    points for the ray in every cube.

5]  What if the user can specify the values in the lattice used
    by the "Noise" function? (Maybe even with turbulence in it!)

Please take a look at the Noise function the sourcefile TEXTURE.c
if you don't understand what I talk about.

I would use such an object to build an asteroid belt approximatly
20 x 20 x length latticepoints large (accomodating approximatly 
10 to 20 asteroids in the width and height directions) and thus having
a maximum of 29 (20 * sqrt(2)) linear equations to solve for a ray
orthogonal to the asteroidbelt. With option [5] if could even specify
a density function such that I have many asteroids in the middle
and a few asteroids near the edges.

/ Mathias Broxvall

PS. I know that I talk more than I implement, but I have implemented
  *some* changes to povray.
.DS

PPS. To "Rolf F. Katzenberger", I could not answer your question
  about a YACC grammar for the parser since your email address
  bounces for me.
.DDS

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