Function face_forward

tutorials/viewer/viewer_device.cpp:198–201

}

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 */
void renderPixelStandard(const TutorialData& data,