Here is one in Gimp, but there should be a photoshop equivalent.

- draw the roofs as solid coloured shapes
- apply a bevel
- duplicate and do an edge detect, that you invert and curve adjust (in multiply mode)
- Gaussian blur the edge layer
- aggressively unsharp mask the blurred layer
- optionally perform a dilate to reduce the heaviness of the lines.

Click image for larger version. 

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-Rob A>