Affine cubic functions. IV. Functions on C
3
, nonsingular at infinity
The object of this paper is to classify cubic functions f on C 3 according to their singularities. A level surface of such a function extends to a cubic surface in projective 3-space. The intersections S^,Tœ of S and its Hessian quartic T with the plane at infinity are the same for all levels. We assume throughout that is a nonsingular cubic curve. In §3 we show how the equisingularity class of Tœ determines the number and multiplicities of critical points of f .In § 2 we investigate n T^, and show that the equisingularity class of the pair (S^Tœ) determines that of f. Next we study the case when some point of has polar quadric a plane-pair; complete enumerations are given in §5 for the case when contains a line, and in §6 for when it contains an Eckardt point of S. In the final section we give a detailed analysis of cases when f has just two critical values, and show how to obtain a complete list of types of functions f.