Improved quadratic normal vector interpolation for realistic shading

Abstract

Interpolation for normal vectors is an important stage of Phong shading. Linear interpolation cannot represent the geometry of surfaces adequately in some situations. Previous quadratic interpolation for normal vectors generates visual artifacts for arch-type curves and triangle scan conversion. To eliminate those artifacts, we propose an improved quadratic interpolation for normal vectors with little computational overhead. Perspective-correct version for obtaining perspective foreshortening is also presented.