Weird light/ shadow effect with displacement

[jvanmid]

Does anyone know what is causing the weird light/ shadow effect in my rendering? It seems to come from corners in my model, but I don't know why. For the bricks I used normal displacement.
Thanks!

[Morbid Angel]

you need to properly tessellate the geometry (can't be nsided) or else the displacement won't work.

[jvanmid]

Thanks for your reply. Can you be more specific? I applied the material to the surface and to the group.

[Morbid Angel]

can you show the wireframe? it has to be equally tessellated with quads.

[jvanmid]

Sorry for the late reply, I had a vacation.
This is the wireframe . In the meanwhile I unchecked background environment (I use a Vray dome) and it seems the weird effect has gone for a large part.

[kenancakir]

You need to draw extra lines..

[jvanmid]

Thanks. I have to draw the line on the surface inside the group?