This article explores non-photorealistic rendering (NPR) techniques for 3D models, focusing on a topological picture book style. The method uses strokes instead of pixels, with silhouettes defined by the zero set of n·v on the mesh. These contours, along with boundaries and double curves, are drawn as tapered ribbons with a pen-like appearance.

The rendering pipeline includes a hidden-line pass for visibility, and hatching is generated from principal curvature directions. Stroke density varies by surface orientation, and line style is tuned for a hand-drawn feel. The approach references classic works by G. K. Francis and modern NPR tutorials.

Key techniques involve smoothing contours, overshooting stroke ends, and controlling ink pooling. The result mimics hand-drawn illustrations with bare paper highlights and ragged bleeds. This style is particularly effective for depicting complex topological surfaces in an intuitive, artistic manner.