Finding arc angles

[_Eduardo_]

Try this, is a modified version of your code.

Perhaps contain some bugs, because I could not verify.

function LWBulgeCalc($xs, $xe, $ys, $ye, $bulge)
{
	$result = array();

	$dx = ($xe - $xs)/2 ;
	$dy = ($ye - $ys)/2 ;
	$a = (1/$bulge-$bulge)/2 ;
	$r = abs($bulge+1/$bulge)*sqrt($dx*$dx + $dy*$dy)/2 ; //Radius circle

	$dr1x =  $dy*$a - $dx ;
	$dr1y = -$dx*$a - $dy ;

	$theta_s = rad2deg(acos($dr1x/$r)) ;
	if($dr1y <  0) $theta_s = 360 - $theta_s ;

	$theta_e = $theta_s + 4*rad2deg(atan($bulge))  ;
	if($theta_e <  0)      $theta_e += 360  ;
	if($theta_e >=  360) $theta_e -= 360  ;


	$result[0] = $xe-$dr1x ;
	$result[1] = $ye-$dr1y ;
	$result[2] = $r        ;
	$result[3] = $theta_s  ;
	$result[4] = $theta_e  ;

	return $result;
}

[odin205]

YES! I guess this is my lucky evening!
I still don't know exactly what I changed but luck is on my side and I changed the right values. Except for closing the drawing, everything goes as planned!

Can you please post your modified code, 'cause i am stuck in the same point, the start and end angles.

I can't find the right conditions to get always the right angles.

[bradodarb]

Hello,

I use this in my geometry lib::

	public static double GetAnglefromPoints(double x1, double y1, double x2, double y2)
        {
            double retval = 0;

            retval = Math.Round(Math.Atan2((y2 - y1),
               (x2 - x1)), 4);

            retval = R2D(retval);

            return retval;

        }

        public static double R2D(double iangle)
        {
            return iangle * (180.0 / Math.PI);
        }

And with GetAnglefromPoints, the first X,Y is center point and the second will either be start or end.


HTH,
Brad Murry