Surface drawing made simple - but not too simple (Q1110255)

Let f(x,y) be a real, single-valued continuous function of two real variables x, y defined over an axes-parallel rectangular domain D. The problem considered was to visualize the surface piece in \(R^ 3\) defined by \(z=f(x,y)\) using line drawing devices. After parallel projection onto an image plane S orthogonal to the viewing direction, hidden-line segments are to be removed. Three different viewing models are considered. A version of the hidden-line removal is presented that generalizes the base of an algorithm of Butland in that (almost) all viewing directions are now allowed. The present solution of the task already treated several times is based on a parametrization via the horizontal position of the image point in S. The visibility of the computed points is exactly determined as opposed to interpolated. A thorough description of the problem is given.