message: Have a random sampler per ray packet
diff: @@ -105,8 +105,6 @@ void tiled_sched<R>::frame(K kernel, SP sched_params, unsigned frame_num)
  sched_params.rt.begin_frame();
  - random_sampler<typename R::scalar_type> samp(detail::tic(typename R::scalar_type{}));
  -
  int w = sched_params.rt.width();
  int h = sched_params.rt.height();
  @@ -119,12 +117,14 @@ void tiled_sched<R>::frame(K kernel, SP sched_params, unsigned frame_num)
  parallel_for(
  pool_,
  tiled_range2d<int>(0, w, dx, 0, h, dy),
  - [&](range2d<int> const& r)
  + [=](range2d<int> const& r)
  {
  for (int y = r.col_begin(); y < r.col_end(); y += ph)
  {
  for (int x = r.row_begin(); x < r.row_end(); x += pw)
  {
  + random_sampler<typename R::scalar_type> samp(detail::tic(typename R::scalar_type{}));
  +
  tiled_sched_impl::call_sample_pixel(
  typename detail::sched_params_has_intersector<SP>::type(),
  R{},
  