Key points are not available for this paper at this time.
Given a three-dimensional array containing values of a function of three variables, the algorithm presented here draws an approximation of the surface or surfaces where the function attains a specified value. This is done by contouring two-dimensional subsets of the three-dimensional array and suppressing the invisible parts of the contours. The union of all the contour line parts approximates the desired surface. The suppression of the invisible lines is the most complicated part of the algorithm and is done by forming a silhouette of the processed subset of the array and testing lines against this structure.
Wright et al. (Wed,) studied this question.