Depending on where they are, they either form cracks in a brick or define a new brick.
It occurred to me these features are similar to procedural tree generation: branches with variables such as turbulance, split angle, and split frequency (and thus proximity). It also bares semblance to fracture.
To test this theory, I looked at other photos to see if it held up.
If the first branch split frequency is high, split variable low, and turbulance low, and rotated with UV mapping, you’d get straight lines with regularlt spaced splits like this:
If the first branch split frequency is high, you’d get something like this:
Other facets I noticed:
- Bricks are distinctly different in tonal pattern and possibly color.
- Aged bricks may have another layer of grime or erosion that blends them together.
- Brick depth may be calmly similar or wildly turbulance. Some bricks are flat, while others are jagged, and everything in between.
- Capstones also vary in surface turbulance
- Larger stones are typically (but not entirely) employed where walls turn or holes constructed.
How to program this procedurally? I don’t think it can be noodled with nodes, but then again, there are some clever folk in Blenderland. If not, surely a script could make short work of these parameters.