gb@vax135.UUCP (Gary Bishop) (08/28/86)
Much to my dismay and horror, I have discovered that the forces of evil succeeded in introducing several errors in our paper "Fast Phong Shading" in the SIGGRAPH'86 proceedings. I am posting the corrections to the net in hopes that they will get to most people who are interested in the method before too many tears are shed. Page 104, first column, first equation. Remove the |L| term from the denominator of the second term. The equation should look like: L Ax + By + C I (x,y) = --- . ------------- diffuse |L| |Ax + By + C| Page 104, first column, second equation Strike the L. from before the Ax, By and C terms in the denominator. The equation should look like: L.Ax + L.By + L.C I (x,y) = ------------------- diffuse |L| |Ax + By + C| Page 104, second column, second equation 2 The first term in the numerator of the equation for T should be 3cg 2 5 not 3ig . The equation should look like: 2 3cg - 4cdi - 4agi T = -------------------- 2 8i sqrt(i) Page 105, first column, second equation The E in this equation is NOT the eye vector. The (Dx + Ey + F) term is meant to interpolate H(x,y). The D, E, and F in this equation are chosen, just as the A,B, and C for N, to interpolate the H vector over the polygon. I am truly sorry for any grief that my errors may have caused anyone trying to understand the method. The errors are purely my own, I bear all the responsibility. Gary Bishop AT&T Bell Labs Holmdel, NJ 07733 (201) 949-3557