public int getInstanceSpan() {
        return instanceSpan;
    }
Sets how this vertex buffer matches with rendered instances
where 0 means no instancing at all, ie: all elements are
per vertex.  If set to 1 then each element goes with one
instance.  If set to 2 then each element goes with two
instances and so on.

@param i the desired number of instances per element
jme3-core/src/main/java/com/jme3/scene/VertexBuffer.java