Vertex animation occurs at the sub-object (vertex) level, for example, moving four vertices in a sphere. A vertex cache is a method to store the vertex animations inside a cache file or point cache file so that the vertex animation is not lost during export from a program. To export the sub-object animation from a program like 3ds Max, every vertex position must be evaluated and stored in cache files.
For sample code that creates and animates vertices using a vertex cache, see functions MapVertexCacheOnTriangle() and AnimateVertexCacheOnTriangle() in the sample program ExportScene03 (see NO LABEL).
For sample code that reads data in a vertex cache, see functions PreparePointCacheData() and ReadVertexCacheData() in the sample program ViewScene (see NO LABEL).
The sample programs are available in <yourFBXSDKpath>\samples\.