"Greg M. Johnson" wrote:
> 
> I'm having fun making flythroughs of the 3dnoise function in the
> superpatch for povray.
> 
> I am trying to understand this mathematically.   If I use:
> 3dnoise(x,y,z)
> I get something with a uniform distribution of porosity.  As the
> threshold approaches 1.0, the percent porosity approaches 0 (% density
> approaches 1.0).  However, if the threshold is 0.0, there is not 100%
> porosity.
> 
> I want to understand how to change the radial density of the noise
> function.  Suppose I want to make a sphere where the density approaches
> 0 at r=R.  How would I do this?  Intuitively, I might try:
> 3dnoise(x^0.5,y^0.5,z^0.5)
> . So far, nothing is yielding precisely the results I'm looking for.

	noise3d (x*f, y*f, z*f)*(R-sqrt(x^2+y^2+z^2)) where f adjusts the
regularity of the noise (the smaller, the smoother). Note that this will
give you some noise outside the sphere too, to avoid this, you could use
noise3d (...)*max(0, R-sqrt(...)) instead.

		Jerome

-- 
*******************************

* they'll tell you what can't * mailto:ber### [at] inamecom
* be done and why...          * http://www.enst.fr/~jberger
* Then do it.                 *
*******************************

Post a reply to this message