Unity 5 has made integration of SpeedTree, see http://blog.speedtree.com/2014/03/1357/

Therefore I have stopped working on my integration. Thank you.

One feature of UnitySpeedTree will be replacing trees in existing scenes. I implemented this feature which replace all trees placed on terrain by Unity terrain tool, so users can easilly upgrade their own levels to UnitySpeedTree vegetation system.

I have done billboarding leaves. Also materials reflect correctly culling attributes provided from SpeedTree modeler, so leaves are rendered from back and front sides and branches from back side only.

Here is the first result of rendering SpeedTree through Unity Graphic.DrawMesh functionality. The result is not same as provided by SpeedTree code, because for now I used some simple shader.

Trees are static so there is no wind yet. I have implemented leaf mesh geometry only so leaves as billboards are not rendered correctly. It will be done in next few days. Also materials are rendered from back side only, leaf cards do not have set culling for front and back side, for example palm leaves are rendered only from one side.

After contacting Unity support I am getting response about described issues previously posted. The native plugin renders geometry at end of frame when scene is completed. So it is not good idea to use it for rendering trees and grass. Also it is why trees and grass are rendered over transparency objects. Shadows are not available through native plugin interface. So the solution is to use integrated rendering pipelite for rendering trees and grass. It means that I stopped working on implementation through native plugin and I will rewrite rendering part to Graphic.DrawMesh function.

I continue working on UnitySpeedTree and I have found issues with using native plugin. Some materials are wrongly mapped when camera angle is changing or when sun is moving. Also there are issues with cutting objects rendered by native plugin in some reflection objects (for example part underwater is still rendered). And transparency does not work correctly as you can see in video (Water 4 Pro).

I have started to integrate SpeedTree into Unity engine one week ago. I am trying to integrate it through Unity low-level native plugin interface. Trees are rendered in scene, but with some material mistakes. Grass is rendered randomly, but with a wrong wind angle.