Origin
Niemeyer, Pietronero, Wiesmann, 1984. Fractal Dimension of Dielectric Breakdown, Phys. Rev. Lett. 52. The eta parameter controls morphology from DLA-like branches to straight needles, traversing an entire spectrum with one slider.
How It Works
A conductor seed sits at the center, a charged boundary surrounds it. The electric potential is solved iteratively via Laplace relaxation. Boundary pixels join the conductor with probability proportional to the local electric field raised to power eta. Re-solve and repeat.
Applications
Models lightning paths, Lichtenberg figures, frost formation, river deltas, mineral dendrites. At eta=1 you get branchy DLA trees, at high eta you get straight needles, intermediate values produce the most beautiful lightning fractals.
click to place conductor seeds·eta controls branch bushiness·steps controls growth per frame