This is just a teaser of a future post about procedurally generated trees. Here you can see an example of the trees I'm currently able to generate. I would have liked it to be a Christmas tree, but I cannot make evergreens right now.
You can click on the image to get a higher resolution view.
It is all voxels, which explains why the tree's crown looks a bit like a cloud. That can be improved at lot, this is something I will discuss later.
I am not using L-systems to generate trees. I did try it, but I was not happy with the amount of input that was required. When it comes to trees apparently there are bigger forces at work than just self-similarity and subdivision.
This is using a technique called Space Colonization. Although I modified this method to make it more efficient, you can find the basics here.