tangent method

Vec3 tangent(
  1. Vec3 a
)

Get the tangent of this vector with respect to a

Implementation

Vec3 tangent (Vec3 a ) {
  double ax = a.x, ay = a.y, az = a.z;

  x = ay * ax - az * az;
  y = - az * ay - ax * ax;
  z = ax * az + ay * ay;

  return this;
}