1. Superquadrics and angle-preserving transformations;Barr;IEEE Computer Graphics and Applications,1981
2. Global and local deformations of solid primitives;Barr;Computer Graphics,1984
3. John C. Hart. Sphere tracing: Simple robust antialiased rendering of distance-based implicit surfaces. Technical Report EECS-93–015, School of EECS, Washington State University, Jan. 1993. Appears in Jules Bloomenthal and Brian Wyvill, Eds., SIGGRAPH ′93 Course Notes #25, “Modeling, Visualizing and Animating Implicit Surfaces.”
4. Geometric clipping using boolean textures;Lorensen,1993
5. Elements of Differential Geometry;Millman,1977