using System;

using OpenTK;

namespace org.niclasundharald.engine
{
	public static class Geometry
	{

		/**
		 * Intersect Triangle and Ray: 
		 * 
		 * A 	+ i * (B-A) + j * (C-A) 			= P +	n * V
		 * A-P 	+ i * (B-A) + j * (C-A) 			= 		n * V
		 * 		  i * (B-A) + j * (C-A) - n * V		= P-A
		 * 
		 * =>
		 * 
		 * -n * V	+ i * (B-A)	+ j * (C-A)			= P-A
		 * 
		 * 
		 **/
		public static bool intersectTriangle(Vector3 P,Vector3 V,Vector3 A,Vector3 B,Vector3 C,out Vector3 p){
			Vector3 BA,CA,PA;

			BA = B-A;
			CA = C-A;
			PA = P-A;

			Console.WriteLine("Interesction:");
			Console.WriteLine("Ray:           {0} + i * {1}",P,V);
			Console.WriteLine("Triangle:      {0}",A);
			Console.WriteLine("               {0}",B);
			Console.WriteLine("               {0}",C);


			if (!Linear.Solve4x3(V,BA,CA,PA,out p)){
				return false;
			}

			p.X = -p.X;
			if (p.X < 0){
				return false;
			}

			if ((p.Y < 0) || (p.Y > 1.0f) ||  (p.Z < 0) || (p.Z > 1.0f)){
				return false;
			}

			p = P + (p.X * V);

			return true;
		}

	}
}