Triangle.h

#ifndef _TRIANGLE_H
#define _TRIANGLE_H

#include "math.h"
#include "Object.h"
#include "Vect.h"
#include "Color.h"

class Triangle : public Object{

	Vect A, B, C;
	Vect normal;
	double distance;
	Color color;

	public:

	Triangle ();

	Triangle (Vect, Vect, Vect, Color);

	// method functions
	Vect getTriangleNormal () { 
		Vect CA (C.getVectX() - A.getVectX(),
				 C.getVectY() - A.getVectY(),
				 C.getVectZ() - A.getVectZ());
		Vect BA (B.getVectX() - A.getVectX(),
				 B.getVectY() - A.getVectY(),
				 B.getVectZ() - A.getVectZ());
		normal = CA.crossProduct(BA).normalize();
		return normal; 
	}
	double getTriangleDistance () { 
		normal = getTriangleNormal();
		distance = normal.dotProduct(A);
		return distance; 
	}
	virtual Color getColor () { return color; }

	virtual Vect getNormalAt (Vect point){
		normal = getTriangleNormal();
		return normal;
	}

	virtual double findIntersection(Ray ray){
		Vect ray_direction = ray.getRayDirection();
		Vect ray_origin = ray.getRayOrigin();

		normal = getTriangleNormal();
		distance = getTriangleDistance();

		double a = ray_direction.dotProduct(normal);


		if( a == 0 ) 
		{ 
			// ray is parrallel to Triangle
			return -1;
		}
		else
		{
			double b = normal.dotProduct(ray.getRayOrigin().vectAdd(normal.vectMult(distance).negative()));
			double distance2plane = -1*b/a;
		
			// Q is point of intersection
			double Qx = ray_direction.vectMult(distance2plane).getVectX() + ray_origin.getVectX();
			double Qy = ray_direction.vectMult(distance2plane).getVectY() + ray_origin.getVectY();
			double Qz = ray_direction.vectMult(distance2plane).getVectZ() + ray_origin.getVectZ();

			Vect Q (Qx, Qy, Qz);


			// [CAxQA] * b >= 0
			Vect CA (C.getVectX() - A.getVectX(),
					 C.getVectY() - A.getVectY(),
					 C.getVectZ() - A.getVectZ());
			Vect QA (Q.getVectX() - A.getVectX(),
					 Q.getVectY() - A.getVectY(),
					 Q.getVectZ() - A.getVectZ());

			double test1 = (CA.crossProduct(QA)).dotProduct(normal);

			// [BCxQC] * b >= 0
			Vect BC (B.getVectX() - C.getVectX(),
					 B.getVectY() - C.getVectY(),
					 B.getVectZ() - C.getVectZ());
			Vect QC (Q.getVectX() - C.getVectX(),
					 Q.getVectY() - C.getVectY(),
					 Q.getVectZ() - C.getVectZ());

			double test2 = (BC.crossProduct(QC)).dotProduct(normal);

			// [ABxQB] * b >= 0
			Vect AB (A.getVectX() - B.getVectX(),
					 A.getVectY() - B.getVectY(),
					 A.getVectZ() - B.getVectZ());
			Vect QB (Q.getVectX() - B.getVectX(),
					 Q.getVectY() - B.getVectY(),
					 Q.getVectZ() - B.getVectZ());

			double test3 = (AB.crossProduct(QB)).dotProduct(normal);


			if( (test1 >= 0) && (test2 >= 0) && (test3 >= 0) ) {
				// inside triangle
				
				return -1*b/a;
			}
			else{
				// outside triangle
				return -1;
			}

		}
	}
	
};

Triangle::Triangle(){
	A = Vect(1,0,0);
	B = Vect(0,1,0);
	C = Vect(0,0,1);
	color = Color (0.5,0.5,0.5,0);
}

Triangle::Triangle( Vect pointA, Vect pointB, Vect pointC, Color colorValue){
	A = pointA;
	B = pointB;
	C = pointC;
	color = colorValue;
}


#endif