Previous work for parametric patches

Raytracing

Whitted(1980): bicubic patches

subdivision approach

Kajiya(1982): bicubic patches

numerical solution

Nishita(1990): trimmed rational Bezier patches

Bezier clipping

Scanline algorithm

Lane(1980): subdivision of curved surface

into polygons at every scan line

Nishita(1991): modification of Lane's method

(subdivision into subpatches at every scan line)