Nice one Bobby. I hadn't looked at the fuzzy zone softness for this... good thinking.
I think it should still work well with a smoothed imaged, particularly for lines at an angle. With an unsmoothed image you will get fine vertical jagged edges along the wall. The antialiasing works at the resolution of the image, so the higher the resolution, the sharper the image looks... so increasing the resolution helps here too.
You could also try using your image map as a displacement function to punch out the stones horizontally.