The Forest
But for the trees, I wanted something very effective. Since the entire project was supposed to be done without additional plugins, and computer generated trees usually look like...well, computer generated trees, I started thinking about doing them manually.
A basic cone with a noise modifier gave me the basic element. Copy, mirror and rotate a few of them to create a small branch. Scale, rotate and mirror again to get some more branches of different sizes, then move them so that everything intersect properly. Mirror rotate and scale some more and you end up with a few basic branches ready to be attached to the top of a loft object acting as the trunk.
It wasn't that easy as described. After all, a tree is not a random collection of sticks with different shape and size. There is a logic, a weight distribution and an overall shape that have to be taken into account.
I created only four different trees. Two big and thick, one short and thick and one short and thin. With them I created all the others, rotating and mirroring as required to give the scene the impression that each tree is unique.