Point based rendering of non-manifold surfaces with contours

We present point based rendering techniques that render various types of contours as constant width slabs on surfaces. The techniques requires evaluations of the surface functions and gradients to render shaded images. We use slabs parallel to the principle planes, slabs located along a principal axis and rotated by arbitrary steps, slabs consisting of concentric spheres and slabs of constant Gaussian and mean curvatures. We also use the technique to render curvature maps of surfaces. We illustrate the techniques with a number of parametric and implicit surfaces, and discuss their advantages and disadvantages compared to other rendering techniques.