The computational effort to render images with light sources and camera at infinity is less than with light sources at finite distance from the illuminated surface. On the other hand, in the case of an infinitely remote light source and camera, planar polygons don’t receive highlights. In this paper, a method is suggested to use the (relatively cheap) infinite-distance model instead of the expensive finite-distance model for the computation of highlights. It works by replacing a light source at finite distance by a light source at infinite distance, and at the same time adjusting the normal vectors in such a way that the resulting illumination pattern stays the same. With these modifications, a simple table look-up comes in the place of an expensive computation to obtain the specular term in the standard illumination model.
Overveld, van, C. W. A. M., & Wyvill, B. (1996). Hi-speed, Hi-fi, Hi-lights : a fast algorithm for the specular term in the Phong illumination model. Journal of Graphics Tools, 1(2), 25-30. https://doi.org/10.1080/10867651.1996.10487457