Function face_forward

tutorials/pathtracer/pathtracer_device.cpp:975–978

} // convertScene

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

inline Vec3fa derivBezier(const ISPCHairSet* mesh, const unsigned int primID, const float t, const float time)
{