--- ray/src/util/ambpos.cal	2014/04/24 23:15:42	2.1
+++ ray/src/util/ambpos.cal	2014/09/03 14:05:55	2.4
@@ -1,7 +1,9 @@
-{ RCSid $Id: ambpos.cal,v 2.1 2014/04/24 23:15:42 greg Exp $ }
+{ RCSid $Id: ambpos.cal,v 2.4 2014/09/03 14:05:55 greg Exp $ }
 {
 	Compute patterns for ambient position markers
 }
+odd(n) : .5*n - floor(.5*n) - .25;
+posangle(a) : if(-a, a + 2*PI, a) / DEGREE;
 { Relative hit point }
 rpx = Px - arg(1);
 rpy = Py - arg(2);
@@ -10,16 +12,24 @@ rpz = Pz - arg(3);
 { Calculation of directional gradient pattern }
 ndx = arg(4); ndy = arg(5); ndz = arg(6);
 dgx = arg(7); dgy = arg(8); dgz = arg(9);
-dg = sqrt(dgx*dgx + dgy*dgy + dgz*dgz);
-dux = (ndy*dgz - ndz*dgy)/dg;
-duy = (ndz*dgx - ndx*dgz)/dg;
-duz = (ndx*dgy - ndy*dgx)/dg;
-dsine = (dux*rpx + duy*rpy + duz*rpz)/sqrt(rpx*rpx + rpy*rpy + rpz*rpz);
-dirfunc = bound(0, 1 + dg*dsine, 2);
+rdx = ndy*rpz - ndz*rpy;
+rdy = ndz*rpx - ndx*rpz;
+rdz = ndx*rpy - ndy*rpx;
+dgrad = (rdx*dgx + rdy*dgy + rdz*dgz)/sqrt(rpx*rpx + rpy*rpy + rpz*rpz);
+dirfunc = bound(0, 1 + dgrad, 2);
 
 { Calculation of positional gradient pattern }
 pgx = arg(4); pgy = arg(5); pgz = arg(6);
 posfunc = bound(0, 1 + (pgx*rpx + pgy*rpy + pgz*rpz), 2);
+				{ corral flags and associated pattern }
+ux = arg(4); uy = arg(5); uz = arg(6);
+cflags = arg(7);
+vx = Ny*uz - Nz*uy;
+vy = Nz*ux - Nx*uz;
+vz = Nx*uy - Ny*ux;
+cflg(i) = if(odd(floor( cflags / 2^i )), 1, -1);
+corralled = cflg(floor(32/360*posangle(
+		atan2(rpx*vx+rpy*vy+rpz*vz, rpx*ux+rpy*uy+rpz*uz) )));
 
 { Calculation of ellipse stencil for base }
 usx = arg(4); usy = arg(5); usz = arg(6);