//==========================================================================================
//			arc_bulge.txt
//	Author: Clif Collins			Date: Jan 2010
//==========================================================================================

//==========================================================================================
//					arcToBulge
//		here bulge = sweep,  AutoCAD bulge = tan(sweep / 2)
//==========================================================================================
function arcToBulge(arc)
{
	var bul,start,sweep,ds;

	bul = new Object();

	x = arc.radius;
	start = arc.start / 180 * Math.PI;
	sweep = arc.sweep / 180 * Math.PI;

	bul.x1 = (x * Math.cos(start)) + arc.cx;
	bul.y1 = (x * Math.sin(start)) + arc.cy;
	bul.x2 = (x * Math.cos(start+sweep)) + arc.cx;
	bul.y2 = (x * Math.sin(start+sweep)) + arc.cy;

	sweep = arc.sweep % 360;
	bul.bulge = sweep;	

	return bul;
}
//==========================================================================================
//					bulgeToArc
//==========================================================================================
function bulgeToArc(bul)
{
	var one,x,y,angle,radius,sdir,edir,mdir,mx,my;
	var dx,dy,length,arc,atan,bulge,tan;

	arc = new Object();
	arc.cx = 0;
	arc.cy = 0;
	arc.radius = 0;
	arc.start = 0;
	arc.sweep = 0;
	arc.rev = false;

	one = 1;
	if (bul.bulge < 0) one = -1;
	bulge = Math.abs(bul.bulge);
	bulge = bulge / 180 * Math.PI;
	bulge = bulge / 2;

	dx = Math.abs(bul.x2 - bul.x1);
	dy = Math.abs(bul.y2 - bul.y1);
	length = Math.sqrt(dx*dx + dy*dy);

	x    = length / 2.0;
	angle = (Math.PI / 2) - bulge;
	tan = Math.tan(angle);
	if (isNaN(tan)) tan = 1;
	y   = tan * x * one;

	arc.radius = Math.sqrt(x*x + y*y)

	if (arc.radius > 1.0E20) return null;

//-------------- Calculate Arc --------------

	angle = lineAngle(bul.x1,bul.y1,bul.x2,bul.y2);
	angle = angle / 180 * Math.PI;

	arc.cx = (Math.cos(angle) * x - Math.sin(angle) * y) + bul.x1;
	arc.cy = (Math.sin(angle) * x + Math.cos(angle) * y) + bul.y1;

	y = y + (arc.radius * (-one));

	mx = (Math.cos(angle) * x - Math.sin(angle) * y) + bul.x1;
	my = (Math.sin(angle) * x + Math.cos(angle) * y) + bul.y1;

//--------------------- Arc Angles ------------------------

	sdir = lineAngle(arc.cx,arc.cy,bul.x1,bul.y1);
	cdir = lineAngle(arc.cx,arc.cy,mx,my);
	edir = lineAngle(arc.cx,arc.cy,bul.x2,bul.y2);

	sdir = (sdir + 360) % 360;
	cdir = (cdir + 360) % 360;
	edir = (edir + 360) % 360;

	ts = Math.max(sdir,edir);
	te = Math.min(sdir,edir);
	tc = cdir;

	sdir = ts;
	edir = te;

	ts = ts - te
	tc = tc - te			// ASSUME ORDERED
	ts = (ts + 360) % 360;
	tc = (tc + 360) % 360;

	if (ts > tc)
	{
		arc.rev = true;
		ts  = sdir;
		sdir = (edir + 360) % 360;
		edir = ts;
	}

//-------------- Set  Arc ------------------

	arc.start = sdir;
	arc.sweep = edir - sdir;
	if (arc.sweep > 360) arc.sweep = (360 - arc.sweep) % 360;

	return arc;
}