3ds Max has displace modifier, which lets you displace real geometry. Not sure if C4D has something similar. But there is a trick in Corona - clean your scene from all unnecessary objects, leave only the plane with Corona material and displacement map plugged in. Export scene to standalone and it will save displaced geometry as proxy file. Now, you only have to load that proxy in your scene and convert it into mesh object. It works well in 3ds Max, hopefully it works in C4D too.