I was looking at Far Cry's vegetation today. They use a small collection of hand-modeled trees and bushes. For a given model, they also have a set of billboards of the model rendered from several viewing directions. (They actually have a high- and a low-rez set of billboards for each model.) For a distant tree, they select the billboard that most closely matches the actual viewing direction. (If you strafe around the tree and change your viewing angle enough, you'll see the tree pop as it switches to a different billboard.)

When you get close enough to a billboard tree, it switches to the 3D model, but you don't see a pop! I would have expected a pop, since the billboard version of the tree is only in approximately the correct orientation. To avoid this, they orient the 3D model so that it matches the billboard. Then, as you approach the tree, the 3D model gradually rotates to the tree's "true" orientation.

Well, anyway, that was my impression of how their system worked. If you want to check it out for yourself, download the demo and focus on the "bent" palms along the beaches.

Hey, Winter Park is a few miles south of me. I suppose you're at Full Sail, yes? Just curious...

Regarding rendering... http://www.vrvis.at/TR/2003/TR_VRVis_2003_027_Abstract.html (the pdf paper is there also) has a summary of different techniques. The "interactive rendering of trees with shading and shadowing" mentioned in there looks the most interesting to me - although the cube map visibility could probably be replaced with some cheaper visibility calc in a vertex shader (eg, polynomial texture map except per-vertex, ambient occlusion, SH, shadow map, etc). Speedtree also looks interesting though not much info - downloading and looking at the valley demo can reveal alot though.

That grass looks pretty sweet man, nice long-field type of grass - what method did you end up using for it? It looks like it might be moving in real-time too but I can't tell from the static shots too well.

-Mezz