Once I was satisfied with the modeling stage I went onto the texturing and lighting. It was not a completely finalized model, but I just decided to stop at that point because it was enough to work with for the texturing and lighting stage. It's always possible to model some more shapes if needed and do another pass of modeling, texturing and lighting.
The final model looked like this (Fig.07).
The background wall is a displaced surface and the bricks under the concrete are 3D models. For the bricks I created a multisub material with three different variations and applied that material to the brick model. Using the Material By Element modifier I randomized those three materials over the brick models to get a natural variation. Keep in mind that when you apply Material By Element you need to have those bricks in one mesh because Material By Element randomly changes material IDs on individual objects inside the collapsed mesh.
Texturing and Materials
Nothing special here; I used VRay materials for everything. I usually don't use anything else except these materials because you can do almost everything you need with them, except maybe high quality sub surface scattering for which there is a new SSS2 material in VRay. The way I am usually working during the texturing and material stage is to build one MultiSubobject material with a couple of different materials that will be used in the scene. For this scene theses were some basic metals, like black, red and gray painted metal surfaces, then more reflective metal materials like bronze, glass and some basic concrete (Fig.08).
Fig.08 - Click to enlarge
After I was done defining the base materials I textured the image based on a combination of those materials. For the UV coordinates, 80% of the time I was using Box UV mapping from the UVW Map modifier. I tried to keep the scale of the Box UV mapping the same for all objects I textured so I could have similar texture scales and a more realistic look. The problem with keeping everything in the same scale is that it's hard because it depends on the scale of the object, so before I did box mapping on every object I went to Utilities and used the Reset XForm option. This kept everything in the same scale so I was safe when applying the Box UV Map. Using this workflow, with multisub material and Box UV mapping, it's very easy to combine materials on the surface. You can make a couple of different variations in 30 minutes and decide which one looks better for you (Fig.09).
Of course base materials were going to be used for some objects in the scene, but not for all of them. The idea here was to quickly texture and combine everything and after that was done, take the objects that were the most important and most visible and redo the UVs and textures on them. So, for example, the front right tower was the one object of that kind. I did a second UV channel on that object and in the Unwrap UVW modifier I used Flatten Unwrapping so that the UVs didn't overlap. Flatten Mapping is separates whole objects into different UV sections based on the angle threshold and it makes the layout of those UVs so there won't be overlapping areas and you won't have distortions. Although this is not very useable for direct painting in Photoshop, it's good for baking dirt. That's the reason why I was keeping this UV in the second channel since I was only using it for the dirt map.
After that I created a material setup for baking the dirt into the edges of that object. I baked that dirt to a separate folder and used that image to drive the Mix map, combining black paint with rusty parts to give the paint a weathered effect. If you don't know how to bake textures, it's in Rendering > Render To Texture. I baked out 4k maps to get as much details as I could. The other reason for that is that since I was using Flatten Mapping, a lot of the UV space was unused, so I was compensating that with a high resolution texture. But if you can spend a little bit more time and create better UVs that use 90% of the UV space then you can probably go with a lower resolution texture for baking.
The material setup for baking and texturing the tower can be seen in Fig.10 - 12.
Fig.10 - Click to enlarge
The lighting was done with VRay's Sun light and one VRay light inside the reactor. It's a very simple setup, and I tried several light setups during the whole texturing/lighting phase. I used several light blockers to get the right shadow placement over the scene. It was done using simple polygon editing to get the shapes I wanted. When positioning light blockers it's good to switch to Light View so you can be more precise - select the light and click Shift+4 for that. You can then get the feeling where your shadows will be cast. The other way to do it is to switch to Orthographic View, match the angle of daylight and then place shadow blockers.
While I am modeling and texturing I like to develop lighting as I go, so these are some of the images I rendered during that process. Lighting is highly dependent on material so that was a big reason why in the end I switched to a completely different light position (Fig.13 - 17).