Here’s a tree I modelled using Maya’s extrude tool.
To make the trunk, I created a polygon cylinder with zero number of caps and deleted all faces except its base circle face. I also drew a curve from the base of the face.
With the face and the curve selected, I fired off the extrude tool. Maya created a cylinder from the base face from one end of the curve to the other.
To make the trunk follow the curve, I adjusted the number of divisions for the extrude history in the trunk’s attributes window. The Taper Curve was also adjusted by clicking and dragging on the graph to make the top end of the trunk thinner.
Once I was happy with the shape of the trunk (adjusting the control ponts of the curve to update the trunk), I drew more curves in the side view for the branches.
Then, like the trunk, I extruded polygon circle faces along the curves and tapered them to create branches.
At this point all branches were coming out at 0 degree or 180 degrees – the tree was flat. To make it look like a tree from all angles, I rotated some branches and adjusted the control points in the top view so they were not just straight.
Now for the leaves. They were just a small rectangular plane that had a transparency mapping. I duplicated several copies of the leaf and and bunched them together and placed them on to the branches. Selecting a branch and clicking on the magnet icon (ie: making the branch ‘live’) ensures that the leaves ‘stick’ to the branch when being translated. For every leaf, making a duplicate copy and rotate it 90 degrees helps the tree look like it has leaves there from all angles.
After quite a lot of duplicating and placing clusters of leaves, the tree looked like this.
To texture the tree, the texture and alpha map for the leaves were replaced with the one below.
For the trunk and branches, the image below was cylindrically mapped.
Some leaves were pruned to make the shape a bit better. The trunk’s normals were softened also so it doesn’t look so faceted.