public static IEnumerable <Vector2> Enumerate(Int32 radiusX, Int32 radiusY, Boolean filled = false)
{
// preliminary check - zero point
if (radiusX == 0 || radiusY == 0)
{
return(Enumerable.Empty <Vector2>());
}
// preliminary check - horizontal line
if (radiusY == 1 || radiusY == -1)
{
return(LineRasterizer.EnumerateHorizontalLine(radiusX));
}
// preliminary check - vertical line
if (radiusX == 1 || radiusX == -1)
{
return(LineRasterizer.EnumerateVerticalLine(radiusY));
}
// potencial problem - negative radius X
if (radiusX < 0)
{
radiusX = -radiusX;
}
// potencial problem - negative radius Y
if (radiusY < 0)
{
radiusY = -radiusY;
}
// enumerates ellipse
return(EnumerateEllipse(radiusX, radiusY, filled));
}
/// <summary>
/// If you wonder why I didn't use some faster algorithm (bresenham, mid-point..) it's because it wouldn't match
/// the outline of drawn ellipse via Graphics.DrawEllipse. So the obstacle looks elsewhere then the drawn ellipse.
/// </summary>
private static IEnumerable <Vector2> EnumerateEllipse(Int32 radiusX, Int32 radiusY, Boolean filled = false)
{
Double anomaly = HalfPi;
Vector2 lastPosition = Vector2.zero;
List <Vector2> result = new List <Vector2>
{
new Vector2(-radiusX, radiusY),
new Vector2(radiusX, radiusY)
};
if (filled)
{
result.Add(Vector2.zero);
}
while (anomaly >= 0.0)
{
Int32 shiftX = Convert.ToInt32(radiusX * Math.Cos(anomaly));
Int32 shiftY = Convert.ToInt32(radiusY * Math.Sin(anomaly));
Int32 x = radiusX + shiftX;
Int32 y = radiusY + shiftY;
if (x != lastPosition.x || y != lastPosition.y)
{
Vector2 topLeft = new Vector2(radiusX - shiftX, radiusY - shiftY);
Vector2 topRight = new Vector2(radiusX + shiftX, radiusY - shiftY);
Vector2 bottomLeft = new Vector2(radiusX - shiftX, radiusY + shiftY);
Vector2 bottomRight = new Vector2(radiusX + shiftX, radiusY + shiftY);
result.Add(topLeft);
if (filled)
{
result.AddRange(LineRasterizer.EnumerateHorizontalLine(radiusX - shiftX + 1, radiusX + shiftX - 1, radiusY - shiftY));
}
result.Add(topRight);
result.Add(bottomLeft);
if (filled)
{
result.AddRange(LineRasterizer.EnumerateHorizontalLine(radiusX - shiftX + 1, radiusX + shiftX - 1, radiusY + shiftY));
}
result.Add(bottomRight);
lastPosition = bottomRight;
}
anomaly -= Step;
}
return(result);
}
