This is a repost from
https://www.therailwire.net/forum/index.php?topic=53305.0, to enable discussions on 3D sculpting and texturing techniques.
I'd be interested in how people model things like wood grain and random shapes like stone (retaining walls).
I have been teaching myself to use Blender for this exact purpose. It is the only free software that I have found so far that can take textures (displacement maps), and apply them in a controlled way on surfaces without needing to manually "sculp" the textures. There are thousands of free texture files available online for every kind of surface from diamond plate, cut stone, wood grain, shingles, cobblestone, cement, dirt, etc. I will say this though, diving into Blender is not for the faint of heart, and is completely unintuitive to my CAD oriented mind. Fortunately I have a cousin who is an artist and animator by trade, so he helps me when I get really stuck in Blender, and I help him with CAD issues. But check out what you can do with it once you get it working properly:
The 3d texture of the shingles is driven by a grey scale displacement map that edits the normal position of each vertex of the mesh.
Youtube will help get you started. This first video will teach you how to apply textures the easy way, but it will only work on top surfaces (displacing texture in the Z+/- direction).
To get textures to work on any 3d surface, you will need to learn UV unwrapping. Think of it as how to unfold a 3d object into a 2d surface, and controlling how those faces are oriented relative to a texture map. Then, instead of using visual textures, you use a displacement map to alter the mesh of the 3d object in a controlled way. By altering the mesh like this, the object is completely 3D printable, instead of just looking like the desired 3d object the way an animator would use visual textures.
There is way more to learn, but this should give you a taste for what is possible and what is involved with this software. I am by no means an expert in blender, just scratching the surface of what it can do. Blender really is a complementary skill to CAD that is worth learning in my opinion, as it opens up a world of possibilities in what we can design and print! I haven't gotten much into the organic sculpting side of things yet beyond simple edits of Thingiverse models, but it seemed relatively straightforward as well.
