I want to make realistic image, but I can’t get that wall covering material right, it looks flat. I cant subdivide mesh because of inappropriate topology (even with simple mode). Any ideas?
Your only choice is textures. I would assume you are using a normal map, which in its settings in the normal map node, you can increase the strength of it.
Another thing would be to get an ambient occlusion (AO) map for that wall texture. You can use it in a mix shader set to multiply with the colour texture to fake in some shadows combined in the colour input of the material shader.
Top is diffuse texture, bottom is AO.
You can set Cycles Feature Set from Supported to Experimental. That can be done right over the drop down where you chose CPU or GPU.
With the experimental feature set you can give your object a subdiv modifier and set it to “simple” instead of “Catmull-Clark” and then check the “adaptive” box. Adaptive will generate geometry only where needed, meaning that geometry closer to the camera will be denser than geometry far a away.
You can then displace as you please.
However, with someting like this it might not makes sense to use displacement and it might make more sense to simply create the geometry by hand. I mean, all you have to do is create one of these planks and then duplicate it a bunch of times. that is probably a lot more efficient when rendering than using displacement.
Join all planks (or at least where it makes sense) to one object because having lots and lots of objects in inefficient as well.
That won’t quite cut it though. If I need to fake shadows and especially shadow gaps (not here), I find I need to modulate the specular as well. Since bump doesn’t create actual shadow by actually modifying the geometry, you need to reduce the specular reflection as well which would also be obscured by actual geometry.
I don’t know what kind of siding that is, but most sidings are fairly easy to setup using some simple math nodes and curves/ramps. And yes, this is faking it. It won’t react properly to a low sun compared to a high sun without tweaking the curves.