SpeedTree artist Sonia Piasecki gives you a quick overview of how to make Clusters in SpeedTree v8.3.0.
Clusters can be used to build the upper branches and leaves structure of a game resolution model.
Cluster documentation: http://docs8.speedtree.com/modeler/doku.php?id=atclusters
PBR documentation: http://docs8.speedtree.com/modeler/doku.php?id=kcpbr
Curves documentation: http://docs8.speedtree.com/modeler/doku.php?id=kccurves
More info at http://www.speedtree.com