Sphere tracing is a new technique for rendering implicit surfaces that uses geometric
distance. Sphere tracing marches along the ray toward its first intersection in steps
guaranteed not to penetrate the implicit surface. It is particularly adept at rendering
pathological surfaces. Creased and rough implicit surfaces are defined by functions with discontinuous or undefined derivatives. Sphere tracing requires only a bound on the magnitude of the derivative, robustly avoiding problems where the derivative jumps or vanishes. It is an efficient direct visualization system for the design and investigation of new implicit models. Sphere tracing efficiently approximates cone tracing, supporting symbolic prefiltered antialiasing. Signed distance functions for a variety of primitives and operations are derived.