public int getMaxNumInstances() {
        return geometries.length;
    }
Set the maximum amount of instances that can be rendered by this
instanced geometry when mode is set to auto.

This re-allocates internal structures and therefore should be called
only when necessary.

@param maxNumInstances The maximum number of instances that can be
rendered.

@throws IllegalStateException If mode is set to manual.
@throws IllegalArgumentException If maxNumInstances is zero or negative
jme3-core/src/main/java/com/jme3/scene/instancing/InstancedGeometry.java