My way o doing that is Material (Roofing Metal) with Relief Pattern.
I use either:
- Relief Pattern > Custom Image - a gray scale or white and black bitmap ( I made it in Photoshop)
or:
- Relief Pattern > Custom Image -Tile ( procedural )
In the attached screencast I've shown both ways.
A more accurate effect could be obtained using a Roofing Tile Material with two maps (made in Photosop) - Generic -a colored realistic image and Bump - a gray scale map for the Relief Pattern . The two bitmaps will work together.
Maybe some of these could help you somehow...
Constantin Stroescu
