code: function cross(a, b, dst) {
    dst = dst || new VecType(3);
  
    const t1 = a[2] * b[0] - a[0] * b[2];
    const t2 = a[0] * b[1] - a[1] * b[0];
    dst[0] = a[1] * b[2] - a[2] * b[1];
    dst[1] = t1;
    dst[2] = t2;
  
    return dst;
  }
docs: Computes the cross product of two vectors; assumes both vectors have
  three entries.
  @param {module:twgl/v3.Vec3} a Operand vector.
  @param {module:twgl/v3.Vec3} b Operand vector.
  @param {module:twgl/v3.Vec3} [dst] vector to hold result. If not new one is created..
  @return {module:twgl/v3.Vec3} The vector a cross b.
  @memberOf module:twgl/v3