--- ray/src/rt/aniso.c	1992/05/20 11:01:40	2.19
+++ ray/src/rt/aniso.c	1993/03/08 12:37:18	2.24
@@ -19,9 +19,11 @@ static char SCCSid[] = "$SunId$ LBL";
 extern double  specthresh;		/* specular sampling threshold */
 extern double  specjitter;		/* specular sampling jitter */
 
+static  agaussamp();
+
 /*
- *	This anisotropic reflection model uses a variant on the
- *  exponential Gaussian used in normal.c.
+ *	This routine implements the anisotropic Gaussian
+ *  model described by Ward in Siggraph `92 article.
  *	We orient the surface towards the incoming ray, so a single
  *  surface can be used to represent an infinitely thin object.
  *
@@ -109,15 +111,15 @@ double  omega;			/* light source size */
 		h[0] = ldir[0] - np->rp->rdir[0];
 		h[1] = ldir[1] - np->rp->rdir[1];
 		h[2] = ldir[2] - np->rp->rdir[2];
-		normalize(h);
 						/* ellipse */
 		dtmp1 = DOT(np->u, h);
 		dtmp1 *= dtmp1 / au2;
 		dtmp2 = DOT(np->v, h);
 		dtmp2 *= dtmp2 / av2;
 						/* gaussian */
-		dtmp = (dtmp1 + dtmp2) / (1.0 + DOT(np->pnorm, h));
-		dtmp = exp(-2.0*dtmp) * 1.0/(4.0*PI)
+		dtmp = DOT(np->pnorm, h);
+		dtmp = (dtmp1 + dtmp2) / (dtmp*dtmp);
+		dtmp = exp(-dtmp) * (0.25/PI)
 				* sqrt(ldot/(np->pdot*au2*av2));
 						/* worth using? */
 		if (dtmp > FTINY) {
@@ -155,15 +157,15 @@ double  omega;			/* light source size */
 			dtmp = 1.0 - dtmp1*dtmp1/dtmp;
 			if (dtmp > FTINY*FTINY) {
 				dtmp1 = DOT(h,np->u);
-				dtmp1 = dtmp1*dtmp1 / au2;
+				dtmp1 *= dtmp1 / au2;
 				dtmp2 = DOT(h,np->v);
-				dtmp2 = dtmp2*dtmp2 / av2;
+				dtmp2 *= dtmp2 / av2;
 				dtmp = (dtmp1 + dtmp2) / dtmp;
 			}
 		} else
 			dtmp = 0.0;
 						/* gaussian */
-		dtmp = exp(-dtmp) * 1.0/(4.0*PI)
+		dtmp = exp(-dtmp) * (1.0/PI)
 				* sqrt(-ldot/(np->pdot*au2*av2));
 						/* worth using? */
 		if (dtmp > FTINY) {