[3dsmax] How to render proper displacement maps (Zdepth render pass? Render to texture...?

Jonathan85

How should i render in a proper way a displacement map from geometry in 3ds max? In particular its a piece of "flatter" rocky ground terrain (surface) (lets say around 3m*3m tile in size)? I saw several techniques. Either "render to texture" (and use the height map  type option) or by simply doing a normal rendering from a top view and using the zdepth pass render element from this rendering. Are both techniques interchangable or is one better than the other?  Os is there other better way how to do this?
(Besides DIsplacement i will probably need also diffuse and maybe other refl. etc. maps).