On 2/19/07, R. William Gosper <rwg@osots.com> wrote:
PPS, I don't see how highlights reflected in a smooth surface with curvature discontinuites will have anything worse than curvature discontinuites. Is there some optical way to differentiate?
The key factor is that motion past a body has the effect of differentiating the surface. Imagine a polished vertical wall, comprising sections of different constant curvatures, meeting at pillars where only the tangent plane is common. Viewed from a stationary location, the wall appears smooth. Walking past a pillar however, the reflection of a circular source alters discontinuously in length, producing a potentially disturbing visual interruption similar to that of a lower-order discontinuity. The effect may be less noticeable in a musical instrument than in the coachwork of an automobile --- I can't claim to have researched the matter! Fred Lunnon