If you generate primitives on a displaced surface, you can add the same Ptex-based vector displacement map to the Description so that primitives get properly positioned and orientated on the displaced surface. For example, if you instance trees on a landscape mesh shaped by a displacement map, adding the map to the Description ensures the trees generate based on the shape of the mesh.
 beside 
				Displacement.
 beside 
				Displacement. 
			 For example:

The position and orientation of primitives now follow the shape of the displaced surface.