Question

Lets say I have an arbitrary vector A. What is the most efficient way to reducing that vectors magnitude by arbitrary amount?

My current method is as follows:

Vector shortenLength(Vector A, float reductionLength) {

    Vector B = A;
    B.normalize();
    B *= reductionLength;
    return A - B;

}

Is there a more efficent way to do this? Possibly removing the square root required to normalize B…

Answer 1

So if I understand you correctly, you have a vector A, and want another vector which points in the same direction as A, but is shorter by reductionLength, right?

Does the Vector interface have something like a "length" member function (returning the length of the vector)? Then I think the following should be more efficient:

Vector shortenLength(Vector A, float reductionLength) 
{
    Vector B = A;
    B *= (1 - reductionLength/A.length());
    return B;
}