# PRINCIPLE

(fractale geometrie)
A recursive subdivision algorithm associated with a process stochatique can generate a pleated surface from a grid mesh quadrilaterals.
Practically, the algorithm is that of Loren Carpenter
(modèle de terrain)
The random values are selected from a random table precomputed (whose dimension, in the initialized envb.h file, can be dynamically changed by the command dim alea). The animation random values are preserved from one image to the next.

## FRACTAL ON VOLUME

frac vol n=t,e,c;
t = fractal type = binary representation of the fractalisation directions:
bit 0: along the vertex normal
bit 1: along the x axis
bit 3: along the y axis
bit 3: along the z axis
e = extension = depth of the recursion
c = random disturbance coefficient

1) yes frac required to activate the fractals.
2) Le coefficient c represents la fraction (random displacement) / (facet size)
Examples:
frac vol 1=1,3,.5; defines fractalisation along the normal, order 3 with random .5
frac vol 1=4,3,-.5; defines fractalisation along y axis, order 3 and random-.5 (inwardly of the volum).
frac vol 1=3,3,.2; defines a fractalisation in a direction normal to the average between the facet and the axis of x.

## FRACTAL SUR UNE FACETTE

frac fac(f)vol(id)=t,e,c; defines a fractalisation on facet f of volume id.
Note:
A geometric discontinuity appear at the junction of two fractalized facets with different coefficients.

(help frac)