Square class

using System;
using Sharp3D.Math.Core;

namespace PathTracer
{
	public class Square:Triangle
	{
		public Square(Vector3F pointA, Vector3F pointB, Vector3F pointC):base(pointA, pointB, pointC) {
		}
		
		
		#region Intersectable implementation
		
		Hitrecord Intersectable.Intersect (Ray r)
		{
			Matrix3F A, Ax;
			float beta, gamma, t;
			Hitrecord hit;
			Vector3F hitPoint;
			Vector3F sol = new Vector3F (pointA.X - r.getOrigin ().X, pointA.Y
				- r.getOrigin ().Y, pointA.Z - r.getOrigin ().Z);

			A = new Matrix3F ();
			A.M11 = pointA.X - pointB.X; A.M12 = pointA.X - pointC.X; A.M13 = r.getDir().X;
			A.M21 = pointA.Y - pointB.Y; A.M22 = pointA.Y - pointC.Y; A.M23 = r.getDir().Z;
			A.M31 = pointA.Z - pointB.Z; A.M32 = pointA.Z - pointC.Z; A.M33 = r.getDir().Z;
			
			if (A.Determinant() < -Material.EPSILON
				|| A.Determinant () > Material.EPSILON) { // solving using
				// Cramer's rule
				float Adet = A.Determinant ();
				Ax = new Matrix3F (A);
				Ax.M11  = sol.X; Ax.M21 = sol.Y; Ax.M31 = sol.Z;
				beta = Ax.Determinant () / Adet;
				Ax = new Matrix3F (A);
				Ax.M21 = sol.X; Ax.M22=sol.Y; Ax.M23 = sol.Z;
				gamma = Ax.Determinant () / Adet;
				Ax = new Matrix3F (A);
				Ax.M31 = sol.X; Ax.M32 = sol.Y; Ax.M33 = sol.Z;
				t = Ax.Determinant () / Adet; // if beta + gamma are
				// between 0 and 1, we're in
				// the triangle.
				if (beta < 1 + Material.EPSILON && gamma < 1 + Material.EPSILON && beta > -Material.EPSILON
					&& gamma > -Material.EPSILON) {
					hitPoint = new Vector3F (r.getDir ());
					hitPoint = Vector3F.Multiply (hitPoint, t);
					hitPoint = Vector3F.Add (hitPoint, r.getOrigin ());
					hit = new Hitrecord (hitPoint, t, getNormal (beta, gamma),
						((Intersectable)this).getMaterial (), this);
					return hit;
				}
			}
			return null;
		}
		
		#endregion		
	
	}
}