.. _`T-NeRF Example`:

T-NeRF 
====================
See code `examples/train_mlp_dnerf.py` at our `github repository`_ for details.

Radiance Field
--------------
Here we implement a very basic time-conditioned NeRF (T-NeRF) model (`examples/radiance_fields/mlp.py`)
for dynamic scene reconstruction.
The implementation is mostly follow the T-NeRF described in the `D-NeRF`_ paper, with a 8-layer-MLP 
for the radiance field and a 4-layer-MLP for the warping field. The only major difference is that
we reduce the max frequency of the positional encoding from 10 to 4, to respect the fact that the
motion of the object is relatively smooth.

.. note::

    The :class:`nerfacc.OccGridEstimator` used in this example is shared by all the frames. In other words, 
    instead of using it to indicate the opacity of an area at a single timestamp, 
    Here we use it to indicate the `maximum` opacity at this area `over all the timestamps`.
    It is not optimal but still makes the rendering very efficient.


Benchmarks: D-NeRF Dataset
---------------------------
*updated on 2022-10-08*

Our experiments are conducted on a single NVIDIA TITAN RTX GPU. 
The training memory footprint is about 11GB.

+----------------------+----------+---------+-------+---------+-------+--------+---------+-------+-------+
| PSNR                 | bouncing | hell    | hook  | jumping | lego  | mutant | standup | trex  | MEAN  |
|                      | balls    | warrior |       | jacks   |       |        |         |       |       |
+======================+==========+=========+=======+=========+=======+========+=========+=======+=======+
| D-Nerf (~ days)      | 32.80    | 25.02   | 29.25 | 32.80   | 21.64 | 31.29  | 32.79   | 31.75 | 29.67 |
+----------------------+----------+---------+-------+---------+-------+--------+---------+-------+-------+
| Ours  (~ 1 hr)       | 39.49    | 25.58   | 31.86 | 32.73   | 24.32 | 35.55  | 35.90   | 32.33 | 32.22 |
+----------------------+----------+---------+-------+---------+-------+--------+---------+-------+-------+

.. _`D-NeRF`: https://arxiv.org/abs/2011.13961
.. _`github repository`: https://github.com/KAIR-BAIR/nerfacc/