Hi @Freemorpheme, there's 2 ways to go about this:
- You sculpt whatever you want and then retopologize (and then UV the retopoed version. Then project the mesh details of your high poly sculpt on that retopoed version via raycasting, which in turn will generate a new high poly model with the proper topology and UVs. Then you bake the maps of this model and use the normal &/or displacement map backon the low poly retopoed UV model)
- You have a base shape in mind and you create the right topology from the start. When the shape looks alright you UV and check the result with a checkerboard texture to check for problematic/stretched areas. If happy, you duplicate your model and subdivide it further to start scultping until you have what you want. Then, most often you end up baking the maps of the high to the low poly.
So the note is: You'll never be able to UV efficiently if topology doesn't allow you to. Good topology makes your life easier every step of the way.
Finally for a rock in C4D start with a Hexaedron sphere, use an FFD defromer to taste and a displacer deformer with a noise to get you started. Keep everything parametric until you have an acceptable shape; UV that, test it with a texture, and then start step 2 above.
You can bake the high poly maps in Substance later.
Hope that helps
VH