public IEnumerable <PointF> GetSpiralPoints()
{
for (float theta = 0;; theta += deltaAngle)
{
var r = thickness * theta;
float x, y;
(x, y) = PointConverter.TransformPolarToCartesian(r, theta);
x += center.X;
y += center.Y;
yield return(new PointF(x, y));
}
}
private bool TryFindPointAtSpiralOneSpinAgo(PointF currentSpinPoint, float a, out PointF previousSpinPoint)
{
var(r, theta) =
PointConverter.TransformCartesianToPolar(currentSpinPoint.X - center.X, currentSpinPoint.Y - center.Y);
theta -= (float)(2 * Math.PI * a);
if (theta < 0)
{
previousSpinPoint = new PointF(0, 0);
return(false);
}
r = theta * a;
var(x, y) = PointConverter.TransformPolarToCartesian(r, theta);
previousSpinPoint = new PointF(x + center.X, y + center.Y);
return(true);
}
public void IEnumerator_YieldsSequenceInCorrectOrder(float thickness, float centerX, float centerY,
int elementIndex)
{
generator = new ArchimedesSpiral(new PointF(centerX, centerY), thickness, DeltaAngle).GetSpiralPoints()
.GetEnumerator();
for (var i = 0; i <= elementIndex; i++)
{
generator.MoveNext();
}
var firstPoint = generator.Current;
generator.MoveNext();
float theta, r;
(r, theta) = PointConverter.TransformCartesianToPolar(firstPoint.X - centerX, firstPoint.Y - centerY);
theta += DeltaAngle;
r = thickness * theta;
var nextX = (float)(r * Math.Cos(theta)) + centerX;
var nextY = (float)(r * Math.Sin(theta)) + centerY;
generator.Current.X.Should().BeApproximately(nextX, (float)Epsilon);
generator.Current.Y.Should().BeApproximately(nextY, (float)Epsilon);
}
