Are isophotes and reflection lines the same?

摘要

Isophotes and reflection lines are standard tools for surface interrogation. We study the correlations between them. We show that isophotes and reflection lines are different (but not disjunct) classes of surface curves. Furthermore we introduce the concept of reflection circles as a generalization of isophotes and reflection lines. Reflection circles can be considered as the mirror images of a family of concentric circles on the surface. We show that reflection circles contain both isophotes and reflection lines as special cases.