--- ray/src/cv/source.cal	1992/10/14 13:21:09	2.4
+++ ray/src/cv/source.cal	1993/12/09 16:58:03	2.7
@@ -3,9 +3,9 @@
 {
 	Source distribution coordinates (degrees).
 
-	Theta is measured from the negative z-axis,
-	phi is measured from the positive x-axis
-	according to the right-hand rule.
+	Theta is measured from the negative z-axis.
+	Phi is measured from the positive x-axis (0 degrees)
+		towards the negative y-axis (90 degrees).
 
 	srcB_vert and srcB_horiz are angles
 	used in type B photometry.
@@ -14,9 +14,12 @@
 	with a rectangular box.  lboxcorr provides a more
 	accurate calculation for nearby surfaces, but requires
 	that the source box be centered at the origin.
+	The dimensions of the box, which must be aligned with
+	the x,y,z axes, are given in meters regardless of the
+	units being used in the scene file.
 
 	A1		- optional multipier
-	A2,A3,A4	- X,Y,Z dimensions of axis-aligned box
+	A2,A3,A4	- X,Y,Z dimensions of axis-aligned box (in meters!)
 }
 					{ local definitions }
 boxprojection = abs(Dx)*A3*A4 + abs(Dy)*A2*A4 + abs(Dz)*A2*A3;
@@ -30,7 +33,7 @@ boxcorr(v) = A1 * v / boxprojection;	{ correction for 
 lboxcorr(v) = A1 * v / lboxprojection;	{ local box correction }
 
 src_theta = Acos(Dz) / DEGREE;			{ 0-180 }
-src_phi = mod( atan2(Dy, Dx) / DEGREE, 360 );	{ 0-360 }
+src_phi = mod( Atan2(Dy, -Dx) / DEGREE, 360 );	{ 0-360 }
 				{ bilateral symmetry }
 src_phi2 = tri( src_phi, 180 );		{ 0-180 }
 				{ quadrilateral symmetry }