1.4.8.1 What is the problem?

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. This image shows two cases where the problem appears:

• 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 is supposed to have a straight one.

Although the artifacts look quite different in nature, they are, in fact caused by the exact same problem.

What one could expect would be something like this image (do not mind about the bright part under the triangle mesh; this is explained later).