SpeedTree 8 has the ability to export directly to Amazon Lumberyard. These exported trees fit into the Lumberyard art pipeline and can be used as individual brushes or in the painted vegetation system, complete with wind bending.
Exporting to Lumberyard is accomplished with that option in the File menu. This will show the standard Game Export Dialog, though a few options will be set for you to facilitate a smooth export to Lumberyard.
Note: Be sure to export directly into your Lumberyard project directory! Texture paths in the materials need to be relative to the root of your project. If you export elsewhere and then copy it in, you will most likely need to update the texture paths in your materials.
Once you export the tree to your Lumberyard project directory, the asset processor will prepare it for use in Lumberyard.
The easiest way to add a single tree is to place it in the scene as a brush. Drag it from the available brushes and into the scene. These trees will be completely static (no wind), however.
A better method for adding trees in bulk is to use vegetation painting. You can paint trees, or groups of trees, with variances on scale and rotation.
When adding trees to the Lumberyard scene as vegetation, you have the option of enabling bending, or wind motion.
Global bending is applied to the tree in the vegetation settings. This just bends the tree over. When active, however, you will also get detail bending, which is enabled on materials where necessary. Detail bending includes smaller branch and leaf motion. The SpeedTree Modeler makes it very easy to tune and preview the wind effects for Lumberyard.