package away3d.tools.utils

{

	import away3d.core.base.data.UV;

	import away3d.core.base.data.Vertex;



	import flash.geom.Vector3D;



	/**

	* Classe returns the uv's from a Vector3D on a triangle plane defined with Vertex objects. Null if outside the triangle definition

	*/

	//credits: http://www.blackpawn.com

	

	public class BaryCentricTest

	{

		private static var _bv:Vector.<Number>;

		/**

		 * Returns the uv's from a Vector3D on a triangle plane defined with Vertex objects. Null if outside the triangle definition

		 *

		 * @param	v0		Vertex. The face v0

		 * @param	v1		Vertex. The face v1

		 * @param	v2		Vertex. The face v2

		 * @param	uv0	UV. The face UV uv0

		 * @param	uv1	UV. The face UV uv1

		 * @param	uv2	UV. The face UV uv2

		 * @param	hit		Vector3D. The intersect point on triangle plane.

		 * @param	uv		[optional] UV. To prevent generation of new UV object return. Optional uv object holder can be passed.

		 */

		 

		public static  function getUVs(v0:Vertex, v1:Vertex, v2:Vertex, uv0:UV, uv1:UV, uv2:UV, hit:Vector3D, uv:UV = null):UV

		{

			if(_bv == null){

				_bv = new Vector.<Number>();

				//v0,v1,v2,dot00,dot01,dot02,dot11,dot12

				for(var i:uint=0;i<14;++i){

					_bv[i] = 0.0;

				}

			}



			var nuv:UV = uv || new UV(0.0,0.0);

			 

			_bv[0] = v2.x - v0.x;

			_bv[1] = v2.y - v0.y;

			_bv[2] = v2.z - v0.z;

			

			_bv[3] = v1.x - v0.x;

			_bv[4] = v1.y - v0.y;

			_bv[5] = v1.z - v0.z;

			

			_bv[6] = hit.x - v0.x;

			_bv[7] = hit.y - v0.y;

			_bv[8] = hit.z - v0.z;

			 

			// Compute dot products

			_bv[9] = _bv[0]*_bv[0]+_bv[1]*_bv[1]+_bv[2]*_bv[2];

			_bv[10] = _bv[0]*_bv[3]+_bv[1]*_bv[4]+_bv[2]*_bv[5];

			_bv[11] = _bv[0]*_bv[6]+_bv[1]*_bv[7]+_bv[2]*_bv[8];

			_bv[12] = _bv[3]*_bv[3]+_bv[4]*_bv[4]+_bv[5]*_bv[5];

			_bv[13] = _bv[3]*_bv[6]+_bv[4]*_bv[7]+_bv[5]*_bv[8];

			

			// Compute barycentric coordinates

			var invDenom:Number = 1 / (_bv[9] * _bv[12] - _bv[10] * _bv[10]);

			var s:Number = (_bv[12] * _bv[11] - _bv[10] * _bv[13]) * invDenom;

			var t:Number = (_bv[9] * _bv[13] - _bv[10] * _bv[11]) * invDenom;

			

			if(s > 0.0 && t > 0.0 && (s + t) < 1.0){

				nuv.u = uv0.u+s*(uv2.u-uv0.u)+t*(uv1.u-uv0.u);

				nuv.v = uv0.v+s*(uv2.v-uv0.v)+t*(uv1.v-uv0.v);

			} else {

				return null;

			}

			

			return nuv; 

		}



	}

}