{ RCSid $Id: ambpos.cal,v 2.1 2014/04/24 23:15:42 greg Exp $ }
{
	Compute patterns for ambient position markers
}
{ Relative hit point }
rpx = Px - arg(1);
rpy = Py - arg(2);
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);

{ 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);

{ Calculation of ellipse stencil for base }
usx = arg(4); usy = arg(5); usz = arg(6);
vsx = arg(7); vsy = arg(8); vsz = arg(9);
ellipstencil = if(1 - sq(usx*rpx + usy*rpy + usz*rpz) - sq(vsx*rpx + vsy*rpy + vsz*rpz),
			1, 0);