/// <summary>
/// Creates an arc with the given center, start, and end points. Performs a check
/// at the given precision to make sure that both the start and end points are
/// the same distance from the center, throwing an exception if they're not. Note
/// that because radius is generated from start point, the resultant arc's start
/// point will be more accurate than the end point.
/// </summary>
/// <param name="center">Center of the arc.</param>
/// <param name="startPoint">Start point of the arc.</param>
/// <param name="endPoint">Point that end angle is projected through.</param>
/// <param name="decimals">Precision at which to check the distance of the endpoints to the center.
/// A negative value will perform an exact check.</param>
public Arc2D(Point2D center, Point2D startPoint, Point2D endPoint, int decimals = 15)
: this(center, center.DistanceTo(startPoint), 0, 0)
{
if ((decimals < 0 && center.DistanceTo(endPoint) != Radius) || (decimals >= 0 && center.DistanceTo(endPoint).RoundFromZero(decimals) != Radius.RoundFromZero(decimals)))
{
throw new Exception("Can't create arc from center and endpoints because endpoints have different distances from the center!");
}
_startAngle = Circle.AngleThroughPoint(startPoint);
_endAngle = Circle.AngleThroughPoint(endPoint);
}
/// <summary>
/// Creates an arc on the given circle with the start angle projected through
/// the start point and the end angle projected through the end point.
/// </summary>
/// <param name="c">Circle that the arc lies on.</param>
/// <param name="startPoint">Point that start angle is projected through.</param>
/// <param name="endPoint">Point that end angle is projected through.</param>
public Arc2D(Circle2D c, Point2D startPoint, Point2D endPoint)
{
this.Circle = c;
_startAngle = c.AngleThroughPoint(startPoint);
_endAngle = c.AngleThroughPoint(endPoint);
}