All tree and grass geometry in the SpeedTree SDK use a wide variety of vertex definitions, which are defined by the options chosen while compiling the SRT files in the Compiler application. Choices like which lighting model is used, wind detail, and how many texture layers can affect the vertex format. For a given tree, it's possible and sometimes likely that each draw call used to render it uses a different vertex declaration.

Unfortunately, variable vertex declarations make it difficult to include pre-defined vertex declaration structures in the SDK, but a set of functions are provided that facilitate convenient access of all of the vertex attributes.