AssetRipper_AssetRipper/Source/AssetRipper.Numerics/GeometricMath.cs

namespace AssetRipper.Numerics;

public static class GeometricMath
{
	private const float kEpsilon = 0.00001F;

	/// <summary>
	/// Angle increase when 2nd line is moving in clockwise direction
	/// </summary>
	/// <returns>Angle in degrees</returns>
	public static float AngleFrom3Points(Vector2 point1, Vector2 point2, Vector2 point3)
	{
		float transformedP1X = point1.X - point2.X;
		float transformedP1Y = point1.Y - point2.Y;
		float transformedP2X = point3.X - point2.X;
		float transformedP2Y = point3.Y - point2.Y;

		double angleToP1 = Math.Atan2(transformedP1Y, transformedP1X);
		double angleToP2 = Math.Atan2(transformedP2Y, transformedP2X);

		double angle = angleToP1 - angleToP2;
		if (angle < 0)
		{
			angle += 2 * Math.PI;
		}

		return (float)(360.0 * angle / (2.0 * Math.PI));
	}
}