Making battlemap scale trees and architectural trees using Bryce 5.5
Bryce 5.5 is a free download from Daz3d - it has a 'tree lab' in it in which you can make trees. It's very rarely used in 3d modelling - the trees don't look all that convincing from the side and they use a lot of polys. But if you want to make individual trees or small clumps of trees in a topdown view they are great.
1. Start Bryce and make the ground plane a flat white texture.
2. Create a tree using the tree primitive button - you'll get the default tree.
3. Edit the tree (select the tree and press the little E button which appears), there are lots of settings - play with them all until you have something you like.
4. Go into 'top view' with the camera and render the tree. Save the image.
5. Go into render options and select 'object mask' and render again to make an alpha mask for your tree. Save the image. Do not move the camera between the two renders or your alpha won't match your colour image.
6. Import both pictures into photoshop / Gimp and use the alpha to make transparent background for your tree.
For architectural trees, use the alpha mask and a 'find edges' filter.
If you like to use vector, use an autotrace on the alpha mask to get a vector image of the tree (as I've done here).
Attached are some of the effects I got, note the bottom one where I selected no foliage which gives you just the brances - the options of different types of tree you can create this way are very wide.