--- ray/src/common/disk2square.c	2011/02/18 00:40:25	3.1
+++ ray/src/common/disk2square.c	2021/12/15 01:39:52	3.6
@@ -1,3 +1,6 @@
+#ifndef lint
+static const char RCSid[] = "$Id: disk2square.c,v 3.6 2021/12/15 01:39:52 greg Exp $";
+#endif
 /*
  *  Disk2Square.c
  *  
@@ -8,7 +11,9 @@
  * Modified interface slightly (G. Ward)
  */
 
+#define	_USE_MATH_DEFINES
 #include <math.h>
+#include "fvect.h"
 
 /*
  This transforms points on [0,1]^2 to points on unit disk centered at
@@ -36,7 +41,7 @@ change log:
 
 /* Map a [0,1]^2 square to a unit radius disk */
 void
-SDsquare2disk(double ds[2], double seedx, double seedy)
+square2disk(RREAL ds[2], double seedx, double seedy)
 {
 
    double phi, r;
@@ -66,7 +71,7 @@ SDsquare2disk(double ds[2], double seedx, double seedy
                 phi = 0.;
        }
    }
-
+   r *= 0.9999999999999;	/* prophylactic against MS sin()/cos() impl. */
    ds[0] = r * cos(phi);
    ds[1] = r * sin(phi);
 
@@ -74,7 +79,7 @@ SDsquare2disk(double ds[2], double seedx, double seedy
 
 /* Map point on unit disk to a unit square in [0,1]^2 range */
 void
-SDdisk2square(double sq[2], double diskx, double disky)
+disk2square(RREAL sq[2], double diskx, double disky)
 {
     double r = sqrt( diskx*diskx + disky*disky );
     double phi = atan2( disky, diskx );
@@ -98,6 +103,6 @@ SDdisk2square(double sq[2], double diskx, double disky
         a = -(phi - 3*M_PI/2) * b / (M_PI/4);
     }
 
-    sq[0] = (a + 1) * 0.5;
-    sq[1] = (b + 1) * 0.5;
+    sq[0] = a*(0.5/0.9999999999999) + 0.5;
+    sq[1] = b*(0.5/0.9999999999999) + 0.5;
 }