acos dividing by zero

[ashstampede]

I'm very lost in the fact that acos is returning ?-1.#IND000

What i am trying to calculate is a angle from two vectors.
now my
"float dot" is a negative number so my assumtion is "that must be why it is returing dived by zero".

//Get the Tanks current Location
	Vector2D Alien = Vector2D();
	Alien.x = m_tank->GetX();
	Alien.z = m_tank->GetZ();

	// Get the Heading of the Tanks turret to a new vector
	Vector2D Heading = Vector2D();
	Heading.x = cursor->GetX();
	Heading.z = cursor->GetZ();

	//location of the Targeted Tank is the Target variable

	//We need to calculate the angle to turn to be centred with 
	//the target.
	
	//What is the direction Vector of the target
	//first subtract the vector
	Vector2D TargetPos = subtractVector(Target,Alien);
	//the normalize it
	normal(TargetPos);
	
	float dot = dotProduct(TargetPos,Heading);
	//the angle of rotation needed
	float theta = acos(dot);
	//convert to degrees.
	ToDegrees(theta);

the functions normal dotProduct are from [link]

http://gpwiki.org/index.php/MathGem:Vector_Operations

[/url]

the subtractVector is a function the subtract each individuall point ie. vec1.x - vec2.x as i didnt know how to overload the - sign for my structure.

thanks in advance.

 

[xwb]

acos will only take values between -1.0 and 1.0. What sort of values are you passing to it? Print statements/couts will help in this case.

 

[ashstampede]

I have sorted it out, it was the normalized, i didnt normalize heading vector so the numbers were over -1 and 1 so sorted. thanks for the response