People often find an annoying problem when applying normal modifier patterns to objects.
It is said that one image tells more than a thousand words, and this saying also applies here. The object in the left of the image is just a regular POV-Ray sphere with a normal modifier made with the bump pattern. The object in right of the image is a mesh of smooth triangles. As you notice, there are two clear artifacts in the image. The sphere has a straight shadow line which seems unnatural and the mesh has a non-straight shadow line when it's supposed to have a straight one.