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https://github.com/google/ldif

3D Shape Representation with Local Deep Implicit Functions.
https://github.com/google/ldif

3d-vision cvpr2020 graphics iccv2019 ldif shape-reconstruction sif

Last synced: 11 days ago
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3D Shape Representation with Local Deep Implicit Functions.

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README 

        
# Overview



![alt text](assets/sif-teaser.png)

![alt text](assets/ldif-teaser.png)



This is a joint codebase for LDIF ([Local Deep Implicit Functions for 3D

Shape](https://arxiv.org/abs/1912.06126)) and SIF ([Learning Shape Templates

with Structured Implicit Functions](https://arxiv.org/abs/1904.06447)). Note

that LDIF was previously called Deep Structured Implicit Functions. It contains

code to reproduce the results of those papers, convert input meshes into the LDIF

and SIF representations, and visualize and extract meshes.

representations.



All .py and .sh files in the top-level

`ldif/` directory are entry points into the code (`train.py`, `eval.py`,

`meshes2dataset.py`, `unit_test.sh`, and `reproduce_shapenet_autoencoder.sh`).

The rest of this README provides information on initial setup and basic

documentation for those files. For additional documentation, please see each file.



## Environment



To set up the LDIF/SIF environment, follow these steps:



#### 1. Set up the python environment



The code was tested with python 3.6 and tensorflow 1.15 on linux. There is a

requirements.txt containing all dependencies.



If you use anaconda, run the following:



```

conda env create --name ldif -f environment.yml

conda activate ldif

```



If you use a system pip installation, run `pip install -r requirements.txt`



After this, the python environment should be ready to go. Please activate the

environment before proceeding. The build scripts include some python.



#### 2. Build GAPS



```./build_gaps.sh```



GAPS is a geometry processing library used by this package to generate the data

and create interactive visualizations. The script `build_gaps.sh` does the

following. One, it installs the necessary dependencies with apt. If sudo is

not available on the system, the requirements are that GAPS have include access

to standard OpenGL and GLu library headers (`GL/gl.h`, `GL/glu.h`) (on both linux and

macos), and that OSMesa static libraries can be linked (on linux). If these are

satisfied, the sudo line can be commented out. Two, it clones the

[GAPS](https://github.com/tomfunkhouser/gaps) repository from GitHub, make some

changes, and builds it. It also moves the qview folder into the gaps repository

and modifies the makefiles. The `qview` executable is a C++ program written using

GAPS to visualize SIF and LDIF representations. Finally, the script compiles all

necessary GAPS C++ executables, which are called by the python code. If this step

was successful, running `./gaps_is_installed.sh` should echo `Ready to go!`



GAPS should compile with no warnings. Please report any warnings by opening a

GitHub issue- the information would be greatly appreciated.



#### 3. Build the inference kernel (Optional, but highly recommended)



```./build_kernel.sh```



If successful, there should be a binary ldif2mesh in the ldif/ldif2mesh/

subdirectory. Note that the inference kernel assumes the CUDA toolkit is

installed and that a gpu supporting compute 6.1 (Pascal, so 10-series or newer)

is available. The nvcc command is part of the CUDA toolkit. If you have an older

gpu, you can try older compute versions for `--gpu-architecture` and `--gpu-code`,

but performance may be reduced and some newer features are used, so it might not

compile.



If you do not want to use the inference kernel or don't have a GPU, then you can

pass `--nouse_inference_kernel` to `eval.py`, which is the only script that

typically calls the kernel. It will then use pure tensorflow ops for evaluating

LDIF, as is done during training (for autodiff support). However, it would be

orders of magnitude slower, so it is really not recommended if more than ~20

meshes need to be evaluated.



The kernel should compile with no warnings. Please report any warnings by

opening a GitHub issue- this information would be greatly appreciated.



## Datasets



To run LDIF/SIF, first a dataset should be made. The input to this step is a

directory of watertight meshes, and the output is a directory containing the

files needed to train and evaluate LDIF/SIF.



Create an input directory somewhere on disk, with the following structure:



```[path/to/root]/{train/val/test}/{class names}/{.ply files}```



The properties of the dataset (# and name of classes, size of the splits, name

of examples, etc.) are determined from the directory structure. If you want to

reproduce the shapenet results, then see `./reproduce_shapenet_autoencoder.sh`. A

dataset doesn't need to have a train, test, and val split, only whichever splits

you want to use. You could make a dataset with just a test split for a

comparison, for example. Note that for convenience the code tries to check if

the class names are wordnet synsets and will convert them to shapenet names

(i.e. 02691156 -> airplane) if they are-- if it can't detect a synset it will

just use the folder name as the class name.



Note that .ply files are required, but the GAPS library provides a shell utility

for converting between file formats. You can do

`./ldif/gaps/bin/x86_64/msh2msh mesh.obj mesh.ply` as an example

conversion, which will read mesh.obj and write a new file mesh.ply to disk.



It is very important that the input meshes be watertight at training time.

GAPS provides a program msh2df that can do the conversion, if you are not

interested in exactly replicating the OccNet experiment's process. Here is an

example command that will make a unit-cube sized mesh watertight:



```

./ldif/gaps/bin/x86_64/msh2df input.ply tmp.grd -estimate_sign -spacing 0.002 -v

./ldif/gaps/bin/x86_64/grd2msh tmp.grd output.ply

rm tmp.grd

```

Msh2df outputs an SDF voxel grid, while grd2msh runs marching cubes to extract a

mesh from the generated SDF grid. The msh2df algorithm rasterizes the mesh to a

voxel grid and then floodfills at a resolution determined by the `-spacing`

parameter in order to determine the sign. The smaller the value, the higher the

resolution, the smaller the smallest allowable hole in the mesh, and the slower

the algorithm. The bigger the value, the lower the resolution, the bigger the

smallest allowable hole in the mesh, and the faster the algorithm. The run time

of both msh2df and of the rest of the dataset creation pipeline will vary greatly

depending on the `-spacing` parameter. The default value of 0.002 is quite high

resolution for a mesh the size of a unit cube.



While msh2df is provided as a utility, it was not used to generate the data for

the trained LDIF+SIF models. For reproducing the shapenet results, please use

the TSDF fusion package used by the

[OccNet repository](https://github.com/autonomousvision/occupancy_networks), not

msh2df.



To actually make a dataset once watertight meshes are available, run:



```

python meshes2dataset.py --mesh_directory [path/to/dataset_root] \

  --dataset_directory [path/to/nonexistent_output_directory]

```



Please see `meshes2dataset.py` for more flags and documentation. To avoid excess

disk usage (and avoid having to pass in the input directory path to all

subsequent scripts), symlinks are created during this process that point to the

meshes in the input directory. Please do not delete or move the input directory

after dataset creation, or the code won't have access to the ground truth meshes

for evaluation.



The dataset generation code writes 7-9mb of data per mesh (about 330GB for

shapenet-13).



## Training



To train a SIF or LDIF, run the following:



```

python train.py --dataset_directory [path/to/dataset_root] \

  --experiment_name [name] --model_type {ldif, sif, or sif++}

```



The dataset directory should be whatever it was set to when running

meshes2dataset.py. The experiment name can be arbitrary, it is a tag used to

load the model during inference/eval/interactive sessions. The `model_type`

determines what hyperparameters to use. ``ldif`` will train a 32x32 LDIF

with 16 symmetric and 16 asymmetric elements. ``sif`` will replicate the

SIF representation proposed in the SIF paper. ``sif++`` will train

an improved version of SIF using the loss and network from LDIF, as well

as gaussians that support rotation, but without any latent codes per element.

By default trained models are stored under `{root}/trained_models/`, but

this can be changed with the ``--model_directory`` flag. For more flags and

documentation, please see `train.py`.



It is also possible to make model types besides the paper version of LDIF/SIF.

For details, please see `ldif/model/hparams.py`. Both LDIF and SIF are stored as

specific hparam combos. Adding a new combo and/or new hyperparameters would be

the easiest way to evaluate how a modification to LDIF/SIF would change the

performance. It would also be how to turn off partial symmetry, or adjust

the number of shape elements or size of the latent codes. The only

special hyperparameter is batch size, which is read directly by the `train.py`

script, and always set to 1 during inference.



While training, the model write tensorboard summaries. If you don't have

tensorboard, you can install it with `conda install tensorboard` or

`pip install tensorboard`. Then you can run



```

tensorboard --logdir [ldif_root]/trained_models/sif-transcoder-[experiment_name]/log

```



assuming that `--model_root` was set to the default `ldif_root]/trained_models/`



Warning: Training an LDIF from scratch takes a long time. SIF also takes a while, though

not nearly as long. The expected performance with a V100 and a batch size of 24 is

3.5 steps per second for LDIF, 6 steps per second for SIF. LDIF takes about 3.5M steps

to fully converge on ShapeNet, while SIF takes about 700K. So that is about 10 days to

train an LDIF from scratch, and about 32 hours for SIF. Note that LDIF performance is

pretty reasonable after 3-4 days, so depending on your uses it may not be necessary to

wait the whole time. The plan is to 1) add pretrained checkpoints (the most pressing

TODO) and 2) add multi-gpu support, later on, to help mitigate this issue. Another

practical option might be switching out the encoder for a smaller one, because most

of the training time is the forward+backward pass on the ResNet50.



## Evaluation and Inference



To evaluate a fully trained LDIF or SIF network, run the following:



```

python eval.py --dataset_directory [path/to/dataset_root] \

  --experiment_name [name] --split {test, val, or train}

```



This will compute metrics over the dataset and then print out the result to the

terminal. By default, it will print out a table of results and LaTeX code. In

addition, there are flags `--save_results`, `--save_meshes`, and `--save_ldifs`,

which can be set to true. If they are set, the code will also write

1) pandas-readable CSV files containing the metrics for each mesh and class,

2) a directory of result meshes generated by the algorithm, and/or

3) a directory of txt files containing the actual LDIF/SIF representation

(parseable by qview, ldif2mesh, and the Decoder class in the ipynb). If these

flags are set, then `--result_directory` must also be provided indicating where

they should be written.



## Interactive Sessions



You can run the code interactively in an Jupyter notebook. To do so, open the

provided file `ldif_example_inference.ipynb` with Jupyter and attach

it to a python 3.6 kernel with the requirements.txt installed. Then follow the

prompts in the notebook. The notebook has a demo of loading a mesh, creating an

example, running inference, visualizing the underlying SIF elements, extracting

a mesh, and computing metrics. There is additional documentation in the .ipynb.



## Unit Tests



There is a script `unit_test.sh`. If you want to check whether the code is

installed correctly and works, run it with no arguments. It will make a small

dataset using open source models and train/evaluate an LDIF network. Note that

it doesn't train to convergence so that it doesn't take very long to run. As a

result, the final outputs don't look very good. You can fix this by setting the

step count in `unit_test.sh` higher (around 50K steps is definitely sufficient).



The code also has some unit tests for various pieces of functionality. To run a

test, cd into the directory of the `*_test.py` file, and run it with no arguments.

Please be aware that not all of the code is tested, and that the unit tests

aren't well documented. The easiest way to check if the code still works is by

running `./unit_test.sh`.



## Other code and PyTorch



In addition to the scripts described above, there are also model definitions and

beam pipelines provided for generating datasets and running inference on a

larger scale. To use these scripts, it would be necessary to hook up your own

beam backend.



There is also very limited PyTorch support in the `ldif/torch` directory. This code

is a basic implementation of SIF that can't train new SIF models, but can load

and evaluate SIFs generated by the tensorflow training+evaluation code. It is mainly

intended for using SIF correspondences as a building block of another unrelated

project in PyTorch. Note that PyTorch is not included in the `requirements.txt`, and

the `torch/` subdirectory is independent from the rest of the code base (it interacts

only through the `.txt` files written by the tensorflow code and takes no dependencies

on the rest of this codebase). To use it, it is probably easiest to just download

the `torch/` folder and import the `sif.py` file as a module.



## Updates to the code



* The code now supports tfrecords dataset generation and usage. This reduces

  the IO workload done during training. It is enabled by default. Existing

  users can git pull, rerun `meshes2dataset.py` with `--optimize` and 

  `--optimize_only`, and then resume training where they left off with the

  new dataset improvements. If you currently experience less than 100% GPU

  utilization, it is highly recommended. Note it increases dataset size by

  3mb per example (and can be disabled with `--nooptimize`).

  

* Support for the inference kernel on Volta, Turing and CC 6.0 Pascal cards

  should now work as intended. If you had trouble with the inference kernel,

  please git pull and rerun `./build_kernel.sh`.

  



## TODOS



This is a preliminary release of the code, and there are a few steps left:



* Pretrained model checkpoints are on the way. In the mean-time, please see

`reproduce_shapenet_autoencoder.sh` for shapenet results.

* This code base does not yet support training a single-view network. In the

  mean-time, the single-view network architecture has been provided (see

  `ldif/model/hparams.py` for additional information).

* While the eval code is fast enough for shapenet, the post-kernel

eval code is written in numpy and is an unnecessary bottleneck. So inference at

  256^3 takes a few seconds per mesh, even though the kernel completes in

  ~300ms.

* Pressing the 'f' key in a qview visualization session will extract a mesh

and show it alongside the SIF elements; however it only considers the analytic

parameters. Therefore, it shows a confusing result for LDIF representations,

  which also have neural features.

* To make setup easier, we would like to provide a docker container

that is ready to go.