Backface culling example npg

	//Create a vector representing the vector from the iDraw to the camera
	Vector toCam;

	toCam = _position - _camera->GetPosition();
	//Normalize toCam so it represents only the direction
	toCam.Normalize();


	//Create a vector representing the heading of a directional light
	Vector toLight(4, NULL);
	toLight(0) = 1;
	toLight(1) = 1.8;
	toLight(2) = 1;

	//Normalize toLight
	toLight.Normalize();

	//Create a vector representing the rotated face normal
	Vector faceNormal;

	//For each face
	for (int i = 0; i < _numFaces; i++)
	{
		//Rotate _faceNormal at i and store
		faceNormal = _faceNormals[i] * _coordinateSystem;

		//Determine color
		//The dot product of two vectors is the magnitude of the vectors multiplied by the cosine of the angle between them
		//Find the dot product of the face normal with the vector representing the direction of the light
		float dotProd = toLight.DotProduct(faceNormal);

		//The dot product between two normalized vectors is the cosine of the angle between them
		//Cosine is bound between -1 and 1. When the angle is 0, PI or any equivilent value the surface must be directly lit and cosine will equal +-1
		//When the angle is PI/2 or any other multiple of the surface is recieving no direct light and should be dark and cosine will equal 0

		//Consider the angle between the faceNormal and the toCam vector
		//When cosine of the angle is positive, the face shouldn't be drawn as it does not face you- it is facing the same direction as you
		//The dot product of the face normal with the normalized toCam vector will return the cosine of the angle between them
		//This is called Backface Culling
		//IF the face is facing us
		if (toCam.DotProduct(faceNormal) <= 0)