// Spit out an endless sequence of bezier segments along a normalized spiral (origo-centered, radius = angle)
static IEnumerable <BezierSpiralSegment> GenerateBezierSpiralSegments(double startAngle, double angleStep)
{
var startPoint = PointOnSpiral.At(startAngle);
while (true)
{
var endPoint = PointOnSpiral.At(startPoint.Angle + angleStep);
var bezier = BezierSpiralSegment.ForSpiralSegment(startPoint, endPoint);
startPoint = endPoint;
yield return(bezier);
}
}
// Creates a BezierSpiralSegment between two points on the spiral.
// Placement of control points is based on https://stackoverflow.com/a/27863181
public static BezierSpiralSegment ForSpiralSegment(PointOnSpiral p0, PointOnSpiral p3)
{
var cpOffset = 4 * Math.Tan((p3.Angle - p0.Angle) / 4) / 3;
return(new BezierSpiralSegment
{
P0 = p0,
P1 = new Point(
x: Math.Cos(p0.TangentAngle) * cpOffset * p0.Angle + p0.Point.X,
y: Math.Sin(p0.TangentAngle) * cpOffset * p0.Angle + p0.Point.Y),
P2 = new Point(
x: Math.Cos(p3.TangentAngle - Math.PI) * cpOffset * p3.Angle + p3.Point.X,
y: Math.Sin(p3.TangentAngle - Math.PI) * cpOffset * p3.Angle + p3.Point.Y),
P3 = p3,
});
}
