int hemisphere_compare(VECTOR* Origin, VECTOR* Destination, ENTITY* Planet)
{
	VECTOR Plane_Normal;
	VECTOR Point;
	int hemisphere;
	
	//get values relative to planet core
	vec_diff(Plane_Normal,Origin,Planet.x);
	vec_diff(Point,Destination,Planet.x);
	//normalize vectors
	vec_normalize(Plane_Normal,1);
	vec_normalize(Point,1);
	
	//calculate hemisphere of Destination
	//relative to a plane-cut oriented by Origin's normal
	hemisphere=vec_dot(Plane_Normal,Point);
	
	if(hemisphere>0)//if on my same hemisphere
	{
		return(1);
	}
	else//if on opposite hemisphere
	{
		return(0);
	}
}

function alignToVec(ANGLE* entAng, VECTOR* vec, VECTOR* axis, var factor) {
	vec_rotate(axis, entAng);
	vec_normalize(axis, 1);
	vec_normalize(vec, 1);
	VECTOR rotAxis;
	vec_cross(rotAxis, vec, axis);
	
	//USE ONLY ONE OF THE FOLLOWING TWO LINES!!!!!!!
	//var angle = -acos((float)vec_dot(axis, vec)) * factor; // instant rotation
	var angle = -acos((float)vec_dot(axis, vec)) * factor * vec_length(rotAxis); //smooth rotation
	
	ANGLE rotAngle;
	ang_for_axis(rotAngle, rotAxis, angle);
	ang_add(entAng, rotAngle);
}

void look_at(ENTITY* Vehicle, VECTOR* Destination, ENTITY* Planet)
{
	VECTOR V_Nrml;
	ANGLE V_Ang;
	VECTOR V_Path;

	// copy my angle
	vec_set(V_Ang, Vehicle.pan);
	
	//get our vehicle's normal from the planet core
	vec_diff(V_Nrml, Vehicle.x, Planet.x);

	// orientate temporary angle as if on a perfect sphere
	alignToVec(V_Ang, V_Nrml, vector(0, 0, 1), 1);
	alignToVec(V_Ang, V_Nrml, vector(0, 0, 1), 1);
	alignToVec(V_Ang, V_Nrml, vector(0, 0, 1), 1);
	alignToVec(V_Ang, V_Nrml, vector(0, 0, 1), 1);
	alignToVec(V_Ang, V_Nrml, vector(0, 0, 1), 1);

	// get destination position relative to the vehicle's orientation
	vec_diff(V_Path, Destination, Vehicle.x);
	vec_rotateback(V_Path, V_Ang);
	
	//DEBUG path
	vec_set(testv1,V_Path);
		vec_normalize(testv1,1000);
		vec_add(testv1,Planet.x);
		draw_line3d(testv1,NULL,100);
		draw_line3d(testv1,COLOR_GREEN,100);
		draw_line3d(Planet.x,COLOR_GREEN,100);

	// convert to an angle
	vec_to_angle(V_Ang, V_Path);
	
	//AVOID GIMBAL LOCK!!!
	if(V_Ang.tilt>85||V_Ang.tilt<-85)
	{
	   return;
	}

	// now, V_Ang's pan is our angle
	ang_rotate(Vehicle.pan, vector(V_Ang.pan, 0, 0));
}

function alignToVec(ANGLE* entAng, VECTOR* vec, VECTOR* axis, var factor) {
	VECTOR locVec, locAxis;
	vec_set(locVec, vec);
	vec_set(locAxis, axis);
	vec_rotate(locAxis, entAng);
	vec_normalize(locAxis, 1);
	vec_normalize(locVec, 1);
	VECTOR rotAxis;
	vec_cross(rotAxis, locVec, locAxis);
	
	//USE ONLY ONE OF THE FOLLOWING TWO LINES!!!!!!!
	//var angle = -acos((float)vec_dot(locAxis, locVec)) * factor; // instant rotation
	var angle = -acos((float)vec_dot(locAxis, locVec)) * factor * vec_length(rotAxis); //smooth rotation
	
	ANGLE rotAngle;
	ang_for_axis(rotAngle, rotAxis, angle);
	ang_add(entAng, rotAngle);
}