SpeedTree's wind effects are implemented through a powerful system that is both flexible and scalable, scaling all the way to cinematic quality used in dozens of feature films. Surprisingly to many, in the games SDK, wind effects are implemented largely by vertex shaders. There are no bones or bone weights used in the simulation. Due to this approach, every instance can have a unique wind signature so that two instances of the same base tree standing right beside each other will have noticeably different wind behavior.
There's also an aggressive but seamless LOD system where hero trees can have fully implemented wind effects up close, but fade those effects to something more modest as the camera moves away, finally to a gentle global sway as the tree turns into a low-res 3D mesh or billboard.
An example of our real-time wind system appears in the video below:
jA3yMnVzrdw ;#; Wind Behavior Preview in SpeedTree Modeler ;#;
Finally, there is a rolling wind effect that really helps to tie a set of trees together to make them look and behave like a single forest. It is particularly effective for grass fields.
Other pages in the wind documentation section cover the details, but the broad strokes of the wind 'pipeline' are as follows:
In the Modeler, there is an AppWizard that's pretty good at taking a solid first shot at tuning a tree model's wind parameters realistically. Users are free to tune its results once the wizard has been executed. The video below shows the results of running the Wind AppWizard on our Coconut Palm model:
GJiY4sG4xb4 ;#; Example Results with Modeler Wind AppWizard ;#;