Uniform
/ random
The seeds, which are the cell centers, are scattered in a random way.


Centered
/ random
More seeds are "spilled" in the center of the terrain. Cells are
smaller in the center. This gives more or less a "hammer blow" effect.
The spacing is proportional to the square of the distance from the
center.


Regular
/ perturbated
The seeds are regularly laid out on the surface. This
gives regular hexagons, with a slight vertical stretch.
The seeds are then moved
by a random amount, in a range specified by the user.
The example shows the effect of a random parameter of 0, 50 (default)
and 100 on a uniform grey image. If you use a height field as noise,
with the random parameter set to 0, the centers would be regularly
spaced, but the lines wouldn't be straight.
Notes:
 The cell size is rounded to the nearest size for giving an
even number of cells rows, otherwise the bottom row would be irregular.
 The hexagons are slightly stretched to produce a tileable
height field. When rendering with Povray, scaling down the Z dimension
by 0.866 should give regular hexagons.


Multiscale
distribution (for uniform and centered cell distribution only)
This options repeats the cracking process at a lower level scale, using
the higher
level boundaries as a guide.
The example shows the effect of a 1x+2x+4x scale.
The crack width is 1 and the grid size
is 5% . First,
the program computes a crack net with a cell size of 20% (4x), with a
width of 4 pixels. On a second step, this net is reused for computing a
crack net with a cell size of 10% and lines of 2 pixels, inside the
bigger cells. The process is repeated a third time to compute 5% cells
into the 10% cells, with boundaries of 1 pixel width.
Hint:
On a 512x512 grid, results are
better when using a size
less than 10% and a crack width of 1. In the case shown, the basic
crack width has been decreased from 2 to 1.
Caution:
This can be a very long
process, particularly when noise is applied and a small cell size is
chosen.


Rendering of a
multiscale crack network with cracknet_bumptest.pov
