--- ray/src/rt/rayinit.cal	1991/11/25 09:51:57	2.2
+++ ray/src/rt/rayinit.cal	1996/10/31 11:05:35	2.11
@@ -9,6 +9,7 @@
 	Nx, Ny, Nz			- surface normal
 	Px, Py, Pz			- intersection point
 	T				- distance from start
+	Ts				- single ray (shadow) distance
 	Rdot				- ray dot product
 	S				- world scale
 	Tx, Ty, Tz			- world origin
@@ -23,6 +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
@@ -45,8 +50,8 @@
 
 	hermite(p0,p1,r0,r1,t)		- 1-dimensional hermite polynomial
 
-	noise3(x,y,z), noise3a(x,y,z),
-	noise3b(x,y,z), noise3c(x,y,z)	- noise function with gradient (-1 to 1)
+	noise3(x,y,z), noise3x(x,y,z),
+	noise3y(x,y,z), noise3z(x,y,z)	- noise function with gradient (-1 to 1)
 
 	fnoise3(x,y,z)			- fractal noise function (-1 to 1)
 }
@@ -56,16 +61,21 @@ AC = arg(0);
 A1 = arg(1); A2 = arg(2); A3 = arg(3); A4 = arg(4); A5 = arg(5);
 A6 = arg(6); A7 = arg(7); A8 = arg(8); A9 = arg(9); A10 = arg(10);
 
+noise3a(x,y,z) : noise3x(x,y,z);
+noise3b(x,y,z) : noise3y(x,y,z);
+noise3c(x,y,z) : noise3z(x,y,z);
+
 			{ Forward compatibility (?) }
 D(i) = select(i, Dx, Dy, Dz);
 N(i) = select(i, Nx, Ny, Nz);
 P(i) = select(i, Px, Py, Pz);
-noise3d(i,x,y,z) = select(i, noise3a(x,y,z), noise3b(x,y,z), noise3c(x,y,z));
+noise3d(i,x,y,z) : select(i, noise3x(x,y,z), noise3y(x,y,z), noise3z(x,y,z));
 
 			{ More robust versions of library functions }
 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);
 
@@ -95,11 +105,11 @@ 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(.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);
-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),
@@ -122,13 +132,13 @@ bspline(pp, p0, p1, pn, t) =	pp * (1/6+t*(-.5+t*(.5-1/
 turbulence(x,y,z,s) = if( s-1.01, 0, abs(noise3(x/s,y/s,z/s)*s) +
 						turbulence(x,y,z,2*s) );
 turbulencea(x,y,z,s) = if( s-1.01, 0,
-			sgn(noise3(x/s,y/s,z/s))*noise3a(x/s,y/s,z/s) +
+			sgn(noise3(x/s,y/s,z/s))*noise3x(x/s,y/s,z/s) +
 			turbulencea(x,y,z,2*s) );
 turbulenceb(x,y,z,s) = if( s-1.01, 0,
-			sgn(noise3(x/s,y/s,z/s))*noise3b(x/s,y/s,z/s) +
+			sgn(noise3(x/s,y/s,z/s))*noise3y(x/s,y/s,z/s) +
 			turbulenceb(x,y,z,2*s) );
 turbulencec(x,y,z,s) = if( s-1.01, 0,
-			sgn(noise3(x/s,y/s,z/s))*noise3c(x/s,y/s,z/s) +
+			sgn(noise3(x/s,y/s,z/s))*noise3z(x/s,y/s,z/s) +
 			turbulencec(x,y,z,2*s) );
 
 			{ Normal distribution from uniform range (0,1) }
@@ -137,13 +147,13 @@ 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);