// as we want the vector as returning value we still
// need a simple int value for checking IF there was an intersection
typedef struct INTERCHECK
{
	int doesIntersect;
	VECTOR intersectionPoint;
}INTERCHECK;

INTERCHECK getLineZPlaneIntersect(VECTOR point1, VECTOR point2) 
{
	vector Intersection;		//this one will hold the intersection point between 
	vector pv;		//this vector will hold the direction vector for the line.
	vector pl;			//and this one is for the line.
	double lambda = 0;		//this is the scalar we need to get the intersection point.
	INTERCHECK result;

	vec_diff(pv, point1, point2);	//getting the difference between the two given points and put it into pv.
	vec_normalize(pv, 1);		//this scales the vector to have a length of 1 but it keeps it's direction	
	if(pv.z == 0)			//if the direction vector has no z-value it is parallel to the Z plane
	{
		//but we still have to check if it EXACTLY lying on the Z plane
		if(point1.z == 0 && point2.z == 0)
		{
			result.doesIntersect = false;
			return result;
		}
	}

	//Okay. as we made it past the parallel-check the line does intersect
	//with the Z plane. Lets get the point.
	lambda = -point1.z/pv.x;	// alright now we have the scalar needed to calculate the freakin intersection point.

	vec_scale(pv, lambda);		// scaling the direction vector by the scalar value to get the right length.
	
	//now we only need to add the scaled direction vector to the origin point.
	vec_set(Intersection, point1);	// this one isn't really needeb but makes things clear.
	vec_add(Intersection, pv);

	//To be really sure we check if Intersection.z == 0. Otherwise this ain't an intersection with the Z plane
	if(!(Intersection.z == 0))
	{
		result.doesIntersect = false;	//ok! this is bad something went wrong if it come to this line!
		return result;
	}
	else
	{
		result.doesIntersect = true;
		result.intersectionPoint = Intersection;
		return result;
	}
}

function whatever()
{
	VECTOR myFirstPoint = vector(1, 5, -3);
	VECTOR mySecondPoint = vector(3, 1, -9);
	INTERCHECK intersectData = getLineZPlaneIntersect(myFirstPoint, mySecondPoint);
	if(intersectData.doesIntersect)
	{
		printf("I got an Intersection at x = %2.3f, y = %2.3f, z = %2.3f!",
			intersectData.intersectionPoint.x,
			intersectData.intersectionPoint.y,
			intersectData.intersectionPoint.z);
	}
	else
		printf("There is no intersection!");
}