/// <summary>
/// Create and arc from three points.
/// </summary>
/// <param name="centre">The centre of the arc.</param>
/// <param name="p1">The starting point</param>
/// <param name="p2">The end point</param>
public MarkGeometryArc(MarkGeometryPoint centre, MarkGeometryPoint p1, MarkGeometryPoint p2)
{
Radius = GeometricArithmeticModule.ABSMeasure(centre, p1);
StartAngle = GeometricArithmeticModule.CalculateAngle(centre, p1);
EndAngle = GeometricArithmeticModule.CalculateAngle(centre, p2);
CentrePoint = centre;
StartPoint = p1;
EndPoint = p2;
Update();
}
/// <summary>
/// see: http://www.lee-mac.com/bulgeconversion.html
/// The curvature of a Polyline Arc segment is defined using a quantity known as bulge.
/// This unit measures the deviation of the curve from the straight line (chord) joining the two vertices of the segment.
/// It is defined as the ratio of the arc sagitta (versine) to half the length of
/// the chord between the two vertices; this ratio is equal to the tangent of a
/// quarter of the included arc angle between the two polyline vertices.
/// </summary>
/// <param name="startPoint"></param>
/// <param name="endPoint"></param>
/// <param name="bulge"></param>
public MarkGeometryArc(MarkGeometryPoint startPoint, MarkGeometryPoint endPoint, double bulge)
{
var d = GeometricArithmeticModule.ABSMeasure(startPoint, endPoint) / 2d;
var r = (d * ((Math.Pow(bulge, 2)) + 1)) / (2 * bulge);
var th = GeometricArithmeticModule.CalculateAngle(startPoint, endPoint) + Math.Acos(d / r);
Radius = Math.Abs(r);
CentrePoint = MarkGeometryPoint.FromPolar(startPoint, th, r);
if (bulge < 0)
{
StartAngle = GeometricArithmeticModule.CalculateAngle(CentrePoint, endPoint);
EndAngle = GeometricArithmeticModule.CalculateAngle(CentrePoint, startPoint);
}
else
{
StartAngle = GeometricArithmeticModule.CalculateAngle(CentrePoint, startPoint);
EndAngle = GeometricArithmeticModule.CalculateAngle(CentrePoint, endPoint);
}
Update();
}
