Convex hull visualization

Chan's ch3d.pdf gives a minimalist optimal 3D divide-and-conquer hull. Points on the hull boundary are white; points strictly inside the hull are bright red (2D and 3D). Use the Variables box for name = expression (one per line); point coordinates can use those names, e.g. (0, a, b) with a = 1, b = 2. Expressions support + − * / ^, parentheses, and constants pi, e. TikZ export draws hull edges with thinner strokes on back-facing triangles and thicker on front-facing ones (camera vs facet normal); the live 3D view uses a uniform wireframe.