Abstract: An approach to ray tracing complex models containing mathematically defined surfaces is presented. Parametric and implicit surfaces, and boolean combinations of these, are first tessellated into triangles. The resulting triangles from many such surfaces are organized into a hierarchy of lists and 3D grids, allowing efficient calculation of ray/model intersections. The technique has been used to ray trace models containing billions of triangles and surfaces never before traced. The organizing scheme developed is also independently useful for efficiently ray tracing any any complex model, whether or not it contains surfaces tessellations.