--- ray/src/rt/rayinit.cal	1992/03/03 13:58:11	2.3
+++ ray/src/rt/rayinit.cal	1993/12/09 16:56:28	2.8
@@ -67,6 +67,7 @@ noise3d(i,x,y,z) = select(i, noise3a(x,y,z), noise3b(x
 bound(a,x,b) : if(a-x, a, if(x-b, b, x));
 Acos(x) : acos(bound(-1,x,1));
 Asin(x) : asin(bound(-1,x,1));
+Atan2(y,x) : if(x*x+y*y, atan2(y,x), 0);
 Exp(x) : if(-x-100, 0, exp(x));
 Sqrt(x) : if(x, sqrt(x), 0);
 
@@ -96,11 +97,11 @@ 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) = .3*r + .59*g + .11*b;
+grey(r,g,b) = noneg(.263*r + .655*g + .082*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);
-clipgrey(r,g,b) = bound(0,grey(r,g,b),1);
+clipgrey(r,g,b) = min(grey(r,g,b),1);
 
 dot(v1,v2) : v1(1)*v2(1) + v1(2)*v2(2) + v1(3)*v2(3);
 cross(i,v1,v2) : select(i,	v1(2)*v2(3) - v1(3)*v2(2),
@@ -138,13 +139,13 @@ un2`private(t) : t - (2.515517+t*(.802853+t*.010328))/
 		(1+t*(1.432788+t*(.189269+t*.001308))) ;
 un1`private(p) : un2`private(sqrt(-2*log(p))) ;
 
-unif2norm(p) : if( .5-p, un1`private(p), -un1`private(1-p) ) ;
+unif2norm(p) : if( .5-p, -un1`private(p), un1`private(1-p) ) ;
 
 nrand(x) = unif2norm(rand(x));
 
 			{ Local (u,v) coordinates for planar surfaces }
 crosslen`private = Nx*Nx + Ny*Ny;
-			{ U is distance from origin in XY-plane }
+			{ U is distance from projected Z-axis }
 U = if( crosslen`private - FTINY,
 		(Py*Nx - Px*Ny)/crosslen`private,
 		Px);