The authors, Gary Bishop and David M. Weiner, have discovered several errors in their paper ``Fast Phong Shading,'' pages 103106 of the SIGGRAPH'86 conference proceedings, Computer Graphics 20(4), August 1986. The authors regret any grief that their errors might have caused anyone trying to understand the method.

Page 104, first column, first equation. Remove the X term from the denominator of the second term. The equation should look like:

Page 104, first column, second equation. Strike the X from before the X, X and X terms in the denominator. The equation should look like:

Page 104, second column, second equation. The first term in the numerator of the equation for X should be X not X. The equation should look like:

Page 105, first column, second equation. The X in this equation is NOT the eye vector. The X term is meant to interpolate X. The X, X, and X in this equation are chosen, just as the X, X, and X for X, to interpolate the X vector over the polygon.