As I advance the modelling stage, I start putting some cracks, broken edges, irregularities on walls and stones. And I never use sharp 90 degree edges on models. They look very unnatural. In nature perfect forms are not exist. Nature is chaotic. 3D MAX has a command which is named "chamfer" to get rid of the right angle edges. This took a lot of time. While working on this kind of images I do not care time. I just try to find the perfect look. I can make endless changings.
I modelled "iron work" using splines. Thats a very enjoyable process. Play with the curves and suddenly you find the perfect curves. After that give thickness to splines. Thats it (see images below)
Advanced modelling and texturing
Most of the times I make detailed modelling and texturing in the same time. Because somethimes it is difficult to decide which detail is texture and which detail is model.
In this project I have old walls, old walls are not totally flat. In time they move slowly in several directions. So if I am drawing an old wall I always put extra segnemts on the prject and move the vertices randomly in different directions. Not much, maybe 2-3 inches can be enough.
Texture or model?:
Somethimes texturing is not enough. If there is a big crack or a broken piece exist on the wall you better model it. Bump effect can not give shadows. Punching the wall by using opacity maps is not very realistic because opacity maps do not give edges thickness.
Therefore, if there are big cracks exist on the wall surface I always model them (see image below).
For the bricks, I mostly use displacement. I increase the number of segments of a plane, prepare a black and white displacement map in photoshop and use that map to give the real 3d brick look (see image below).
I prepared all textures in photoshop. They are very large files. Some of them are 7000x7000 pixels. When you want to render your scene in high resolutions, you need higher resolution textures.
I used some real photograps to crop the crack images from them (see image below).