thanks again for changing loginname
ok back to voxel trees:
yes sure the 3dLogo is not a new idea, i wrote the link to wikipedia there are links and the example of the tree is made with a python-3dLogo i think

@xelons: Turtlegraphics use commands like setpos, pendown, penup and forward instead of direct draw-commands "normally" used. you change the position of the turtle and draw from there (or in this case a voxel it the pen is down). i used for the positon of the turtle the private variable pos its a polyvoxvector, see polyvoxdoku. and setvoxel sets a voxel at position.
PolyVox::Vector3DFloat pos;

and the method changes it, or i changed it directly (not good style?)
void SetPos(int X, int Y, int Z)
{
pos.setX(X);
pos.setY(Y);
pos.setZ(Z);
}

you dont have to use a polyvoxvector but if you want to use vectormathematics there are already some commands in polyvox to calculate with them and if you want to use polyvox why not use them?

on vterraindotorg is good database of knowledge:
http://vterrain.org/Plants/