Key points are not available for this paper at this time.
This paper describes two algorithms which find the visible portions of surfaces in a picture of a cluster of three-dimensional quadric patches. A quadric patch is a portion of quadric surface defined by a quadratic equation and by zero, one, or several quadratic inequalities. The picture is cut by parallel planes called scan planes. The visibility problem is solved in one scan plane at a time by making a "good guess" as to what is visible according to the visible portions found in the previous scan plane.
Rogério Luís Mahl (Sat,) studied this question.