Triangle.h

#ifndef Triangle_H
#define Triangle_H

#include "math.h"
#include "Object.h"
#include "Vect.h"
#include "Color.h"
#include "Ray.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 parallel to the Triangle
			return -1;
		}
		else {
			double b = normal.dotProduct(ray.getRayOrigin().vectAdd(normal.vectMult(distance).negative()));
			double distance2plane = -1*b/a;
			
			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);
			
			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);
			
			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);
			
			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)){
				return -1*b/a;
			}
			else {
				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 a, Vect b, Vect c, Color colorValue) {
	A = a;
	B = b;
	C = c;
	color = colorValue;
}

#endif