/// <summary>
/// Returns circles that are tangent to another circle and line.
/// </summary>
/// <param name="circle">Circle that returned circles should be tangent to.</param>
/// <param name="line">Line that returned circles should be tangent to.</param>
/// <param name="radius">Radius of new circles.</param>
/// <returns>External tangent circles are listed first.</returns>
public static Circle2D[] FromTangentTangentRadius(Circle2D circle, LineSeg2D line, decimal radius)
{
List <Circle2D> orbits = new List <Circle2D>();
LineSeg2D[] parallels = new LineSeg2D[2];
List <Point2D> centerPoints = new List <Point2D>();
List <Circle2D> tangentCircles = new List <Circle2D>();
orbits.Add(new Circle2D(circle.X, circle.Y, circle.Radius + radius));
if (radius < circle.Radius)
{
orbits.Add(new Circle2D(circle.X, circle.Y, circle.Radius - radius));
}
parallels = line.GetParallels(radius);
foreach (Circle2D orbit in orbits)
{
for (int i = 0; i <= 1; i++)
{
centerPoints.AddRange(orbit.GetIntersect(parallels[i]));
}
}
for (int i = 0; i <= centerPoints.Count - 1; i++)
{
tangentCircles.Add(new Circle2D(centerPoints[i].X, centerPoints[i].Y, radius));
}
return(tangentCircles.ToArray());
}
/// <summary>
/// Returns circles that are tangent to two lines.
/// </summary>
/// <param name="lineA">First line.</param>
/// <param name="lineB">Second line.</param>
/// <param name="radius">Radius of the tangent circles.</param>
/// <returns>Will return no circles if the two lines are parallel or the same line.</returns>
public static Circle2D[] FromTangentTangentRadius(LineSeg2D lineA, LineSeg2D lineB, decimal radius)
{
List <LineSeg2D> parallels = new List <LineSeg2D>();
Nullable <Point2D> centerPoint = default(Nullable <Point2D>);
List <Point2D> centerPoints = new List <Point2D>();
List <Circle2D> tangentCircles = new List <Circle2D>();
parallels.AddRange(lineA.GetParallels(radius));
parallels.AddRange(lineB.GetParallels(radius));
for (int i = 0; i <= parallels.Count - 2; i++)
{
for (int j = i + 1; j <= parallels.Count - 1; j++)
{
centerPoint = parallels[i].GetIntersect(parallels[j], true);
if (centerPoint.HasValue)
{
centerPoints.Add(centerPoint.Value);
}
}
}
for (int i = 0; i <= centerPoints.Count - 1; i++)
{
tangentCircles.Add(new Circle2D(centerPoints[i].X, centerPoints[i].Y, radius));
}
return(tangentCircles.ToArray());
}
