Function face_forward

tutorials/user_geometry/user_geometry_device.cpp:738–741

}

inline Vec3fa face_forward(const Vec3fa& dir, const Vec3fa& _Ng) {
  const Vec3fa Ng = _Ng;
  return dot(dir,Ng) < 0.0f ? Ng : neg(Ng);
}

/* task that renders a single screen tile */
Vec3fa renderPixelStandard(const TutorialData& data,