Quaternion from and to Angle/Axis

//-----------------------------------------------------------------------
quaternion &quaternion::fromAngleAxis(const float angle, const vec3 &axis)
{
    float halfAngle = angle * 0.5f;
    float scale = sin(halfAngle) / axis.magnitude();

    x = axis.x * scale;
    y = axis.y * scale;
    z = axis.z * scale;
    w = cos(halfAngle);

    return *this;
}

//-----------------------------------------------------------------------
void quaternion::toAngleAxis(float &angle, vec3 &axis) const
{
    float halfAngle = acos(w);
    float scale = 1.0f / sin(halfAngle);

    angle = halfAngle * 2.0f;
    axis.x = x * scale;
    axis.y = y * scale;
    axis.z = z * scale;
}