Abstract: This paper presents a new method for progressively previewing a ray-traced image while it is being computed. Our method constructs and incrementally updates a constrained Delaunay triangulation of the image plane. The points in the triangulation correspond to all of the image samples that have been computed by the ray tracer, and the constraint edges correspond to various important discontinuity edges in the image. The triangulation is displayed using hardware Gouraud shading, yielding a piecewise-linear approximation to the final image. Texture mapped surfaces, as well as other regions in the image that are not well approximated by linear interpolation, are handled with the aid of hardware texture mapping.