gistfile1.cpp

void DrawTriangular::calculatePoints(Vector3D point1, Vector3D point2, Vector3D point3, img::Color color){
  double oneZ = 1/(3*point1.z) + 1/(3*point2.z) + 1/(3*point3.z);

	//project those points
	this->projectPoint(point1);
	this->projectPoint(point2);
	this->projectPoint(point3);

	double xG = (point1.x + point2.x + point3.x)/3;
	double yG = (point1.y + point2.y + point3.y)/3;

	int yMin = roundToInt(std::min(std::min(point1.y, point2.y), point3.y) + 0.5);
	int yMax = roundToInt(std::max(std::max(point1.y, point2.y), point3.y) - 0.5);

	//std::cout << "yMin " << yMin << "   yMax" << yMax << std::endl;

	if(yMin == yMax){
		// No calculation possible, stop at this moment
		return;
	}

	double posInfinity = std::numeric_limits<double>::infinity();
	double negInfinity = -std::numeric_limits<double>::infinity();


	//AB -> point1 - point2
	//BC -> point2 - point3
	//CA -> point3 - point1

	// our lines

	// Now start looping between YMin and YMax
	for(int i = yMin;i <= yMax;i++){
		double XlAB = posInfinity;
		double XlCA = posInfinity;
		double XlBC = posInfinity;

		double XrAB = negInfinity;
		double XrCA = negInfinity;
		double XrBC = negInfinity;


		if((i-point1.y)*(i-point2.y) <= 0 and point1.y != point2.y){
			XlAB = point1.x + (point2.x - point1.x)*( (i-point1.y) / (point2.y-point1.y));
			XrAB = point1.x + (point2.x - point1.x)*( (i-point1.y) / (point2.y-point1.y));
		}

		if((i-point2.y)*(i-point3.y) <= 0 and point2.y != point3.y){
			XlBC = point2.x + (point3.x - point2.x)*( (i-point2.y) / (point3.y-point2.y));
			XrBC = point2.x + (point3.x - point2.x)*( (i-point2.y) / (point3.y-point2.y));	
		}

		if((i-point1.y)*(i-point3.y) <= 0 and point1.y != point3.y){
			XlCA = point3.x + (point1.x - point3.x)*( (i-point3.y) / (point1.y-point3.y));
			XrCA = point3.x + (point1.x - point3.x)*( (i-point3.y) / (point1.y-point3.y));
		}

		int Xl = roundToInt(std::min(std::min(XlAB, XlBC), XlCA));
		int Xr = roundToInt(std::max(std::max(XrAB, XrBC), XrCA));

		Vector3D u = point2 - point1;
		Vector3D v = point3 - point1;
		Vector3D w;

		w.x = u.y*v.z - u.z*v.y;
		w.y = u.z*v.x - u.x*v.z;
		w.z = u.x*v.y - u.y*v.x;

		double k = (w.x * point1.x) + (w.y * point1.y) + (w.z * point1.z);

		double dzdx = w.x/(-d*k);
		double dzdy = w.y/(-d*k);

		for(int j = Xl;j < Xr;j++){
			double pixelZValue = 1.0001*(1/oneZ) + (j-xG)*dzdx + (i-yG)*dzdy;
			pixelZValue = 1/pixelZValue;

			//do we need to draw?
			if(buffer.redraw(j, i, pixelZValue)){
				this->image(j, i) = color;
			}
		}
	}