I am trying to model a tree and instead of using a bunch of cylinders I wanted to use a bezier curve and outline a tree. However spin doesn’t work, and then I convert it to a mesh and extrude, it becomes a square object instead of round. I don’t know of any modifier that can do that. Bevel doesn’t work either.
Ok so to be honest i am a huge fan of box modeling, I would find a dead tree or one without leaves and use it as a template and extrude, extrude and extrude some more, make cuts and extrude and so on, then apply sub-surf modifier to get the roundness. keep the polys as low as possible and systematically add more detail. good luck!
The add on Dito mentions is a great one. If you want to make a tree yourself, try this method: https://www.youtube.com/watch?v=l8LkOMU8OMg He starts with the tree at around 5.30.