--- ray/src/rt/rayinit.cal	1993/12/09 16:56:28	2.8
+++ ray/src/rt/rayinit.cal	1996/02/29 11:13:34	2.10
@@ -24,6 +24,10 @@
  	RdotP				- perturbed ray dot product
  	CrP, CgP, CbP			- perturbed material color
 
+	For prism1 and prism2 types, the following are available:
+
+	DxA, DyA, DzA			- direction to target light source
+
 	Library functions:
 
 	if(a, b, c)			- if a positive, return b, else c
@@ -97,7 +101,7 @@ noneg(v) = if(v,v,0);
 red(r,g,b) = if(r,r,0);
 green(r,g,b) = if(g,g,0);
 blue(r,g,b) = if(b,b,0);
-grey(r,g,b) = noneg(.263*r + .655*g + .082*b);
+grey(r,g,b) = noneg(.265074126*r + .670114631*g + .064811243*b);
 clip_r(r,g,b) = bound(0,r,1);
 clip_g(r,g,b) = bound(0,g,1);
 clip_b(r,g,b) = bound(0,b,1);