Does this do what I want it to do?

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Does this do what I want it to do?

Does this do what I want it to do?

I'm trying to make a first person asteroid shooter game and I'm running into some difficulties with the math. I discovered that in order to turn a ship relative to itself, I need to be able to revolve a vector around another vector. This is above my current math skills so I just went to this website:

http://blog.kjeldby.dk/2008/10/rotation-around-an-vector-in-cxna/

and basically plugged it right into my code:

void Vector3D::revolveAround (const Vector3D &b, double degrees)
{
    // convert the degrees to radians
    double angle = degrees * M_PI / 180;

    // Set up the rotational matrix
    // a1 a2 a3
    // b1 b2 b3
    // c1 c2 c3
    double a1 = ((1 - cos (angle)) * b.x * b.x) + cos (angle);
    double a2 = ((1 - cos (angle)) * b.x * b.y) - (sin (angle) * z);
    double a3 = ((1 - cos (angle)) * b.x * b.z) + (sin (angle) * y);

    double b1 = ((1 - cos (angle)) * b.x * b.y) + (sin (angle) * z);
    double b2 = ((1 - cos (angle)) * b.y * b.y) + cos (angle);
    double b3 = ((1 - cos (angle)) * b.y * b.z) - (sin (angle) * x);

    double c1 = ((1 - cos (angle)) * b.x * b.z) - (sin (angle) * y);
    double c2 = ((1 - cos (angle)) * b.y * b.z) + (sin (angle) * x);
    double c3 = ((1 - cos (angle)) * b.z * b.z) + cos (angle);

    // The final vector
    Vector3D temp (*this);

    temp.x = a1 * x + a2 * y + a3 * z;
    temp.y = b1 * x + b2 * y + b3 * z;
    temp.z = c1 * x + c2 * y + c3 * z;

    *this = temp;
    
    return;
}

but I'm worried, because if this doesn't work, I'm not going to have a clue how to fix it. Is the math sound?

thepedestrian (200)

Note that I haven't troughly gone through the link in your post but the idea is pretty basic here.

Pretty much you have a matrix that will describe your position.

For example, matrix below represents a set of points (A, B) that form a line with slope 1. Now if I wanted to reflect this matrix about the Y-axis, I would want to multiply it by a value (a matrix) such that a point is now [-1, 1]:

What I'm giving:
    A   B
X  [1   0]
Y  [1   0]

What I'm multiplying by:
    A   B
X  [1   0] [-1 0]
Y  [1   0] [0  1]

Reflected (what I want):
    A   B
X  [1   0] [-1 0]   =  [-1 0]
Y  [1   0] [0  1]   =  [1  0]

I just simple points put inside a matrix to illustrate the basic point but you can do this with vectors as well. The notion I've shown is very common.