Self organized random dichotomic "sunny" trees. New twig is rejected if it is shadowed (there is a neighbour above). 128×128 array is used to store top heights. "Shadowing" trees are fast and funny (I'm not sure if foliation is accurate (not self intersected).
As by product of shadowing test we get simple 128×128 shadow map texture.
It is not very difficult to make big forest demo with fixed allowed pathway and fixed LOD.

More realistic demo with shadows.
Demo with distance checking.