Why a scene render might have many very dark triangle artifacts? It was imported from obj and the scene has some environment light and a lot of sun light (the only way to make shadows more contrast I found).



.blend file: https://yadi.sk/d/UEUud0Y93HWBUH

Thank you!
In edit mode press A, so that the whole mesh is selected. Then press Ctrl+N (this fixes the normals of an object, normal essentially tell the render engine which way the face is facing). Then press W and select delete doubles.