Learning Neural Parametric Head Models (NPHM)

Paper | Video | Project Page

This repository contains the implementation of the paper:

Learning Neural Parametric Head Models

Simon Giebenhain, Tobias Kirschstein, Markos Georgopoulos, Martin Rünz, Lourdes Agaptio and Matthias Nießner
CVPR 2023

If you find our code, dataset or paper useful, please consider citing

@inproceedings{giebenhain2023nphm,
 author={Simon Giebenhain and Tobias Kirschstein and Markos Georgopoulos and  Martin R{\"{u}}nz and Lourdes Agapito and Matthias Nie{\ss}ner},
 title={Learning Neural Parametric Head Models},
 booktitle = {Proc. IEEE Conf. on Computer Vision and Pattern Recognition (CVPR)},
 year = {2023}}

Contact Simon Giebenhain for questions, comments and reporting bugs, or open a GitHub Issue.

Installation

First you have to make sure that you have all dependencies in place. The simplest way to do so, is to use anaconda.

You can create an anaconda environment called nphm using

conda create -n "nphm" python=3.9
conda activate nphm

To install this repository and its requirements in development mode run

pip install -e .

If you plan to run a model you will need have a GPU-enabled pytorch version running. For our experiemnts we used pytorch 1.13 and CUDA 11.6.
During training this code uses wandb for logging purposes. wandb needs to be installed additionally, or removed from the code.

Environment Paths

For simplicity we maintain a python file env_paths.py that defines all relevant paths, e.g. for the dataset, model checkpoints, inference results etc.
You will have to modify these values to suit your machine. In case you work with multiple different machines you can remove env_paths.py from the version control of git via

git rm --cached src/NPHM/env_paths.py

which allows to have a differnt version for different machines.

Dataset

We provide detailed information on our dataset here.

Demo

Exploring our Data

For a first look at our please have a look here.

Fitting Point Clouds

After downloading our pretained models, as described here, you can perform reconstruction using

python scripts/fitting/fitting_pointclouds.py -cfg_file scripts/configs/fitting_nphm.yaml -exp_name EXP_NAME -exp_tag EXP_TAG -resolution 256 -demo

Random Sampling

You can generate randomly sampled heads in neutral expression using

python scripts/fitting/fitting_pointclouds.py -cfg_file scripts/configs/fitting_nphm.yaml -exp_name EXP_NAME -exp_tag EXP_TAG -resolution 256 -sample

Data Preparation

Before you can start training you will need to prepare the dataset into a form that can be directly used for supervision.

To train the identity model we prepare samples on the surface for the neutral expression scan for each person, using

python scripts/data_processing/sample_surface.py 

To prepare samples of the forward deformation fields (warping from neutral expression to any other expression of a person) run

python scripts/data_processing/sample_deformation_field.py

Note that this supervision is based on our registered meshes in fixed template topology. It is also restricted to supervise the facial area.

You can state your desired output paths in env_paths.SUPERVISION_IDENTITY and env_paths.SUPERVISION_DEFORMATION_OPEN, respectively.

NOTE: Note that the generated files will take up around ~320GB

Training

NPHM is trained in two stages.

Stage 1 - Learning Geometry in Neutral Expression

First you need to train the identity space using

python scripts/training/train.py -cfg_file scripts/configs/nphm.yaml -local -exp_name SHAPE_EXP_NAME 

To train NPM instead use npm.yaml instead and omit the -local argument.

Stage 2 - Learning Forward Deformations

Afterwards, the expression space can be trained:

python scripts/training/train_corresp.py -cfg_file scripts/configs/nphm_def.yaml -exp_name EXPRESSION_EXP_NAME -mode compress

Make sure that the nphm_def.yaml includes the correct experiment name and epoch in the shape_exp_name and shape_ckpt fields. For NPM use npm_def.yaml and -mode npm.

Pretrained Models

You can download pretrained NPM and NPHM models here. Place the files into env_paths.EXPERIMENT_DIR/

Inference

Test Set

We evaluate our models by fitting back-projected single view point clouds.
More specifically, we propose a test set consisting of 23 identities, with varying number of expressions raning from 7 to 24 expressions. In total it contains 427 scans. Each expression is observed from a randomly, slightly varying frontal view. Additionally each person is observed once from the back. Each observation consists of 2500 3D points.

For inference run

python scripts/fitting/fitting_pointclouds.py -cfg_file scripts/configs/fitting_nphm.yaml -exp_name EXP_NAME -exp_tag EXP_TAG -resolution 400

which optimizes one identity and all expression codes jointly for each person. Results are stored in env_paths.FITTING_DIR/EXP_NAME/EXP_TAG/. The models as well as checkpoints are specified in scripts/configs/fitting_nphm.yaml. For NPM use scripts/configs/fitting_npm.yaml instead.

Evaluation

Metrics against our ground truth scans can be computed using

python scripts/evaluation/eval.py --results_dir FITTING_DIR/forward_EXP_NAME/EXP_TAG/

We compute Chamfer-L1, Chamfer-L2, Normal Consistency and F-Scores @1mm and @5mm. All those metrics are computed in a point-based-fashion, i.e. points (and normals) are sampled on reconstruction and ground truth to compute the metrics. These samples are generated by rendering and back-projecting random views of the meshes, such that models, that reconstruct the mouth interior even if it is closed, are not punished excessively.

Finally, metrics over the full test set are gathered using

python scripts/evaluation/gather.py --results_dir FITTING_DIR/forward_EXP_NAME/EXP_TAG/

which outputs two files FITTING_DIR/forward_EXP_NAME/EXP_TAG/evaluation/total_metrics.csv and FITTING_DIR/forward_EXP_NAME/EXP_TAG/evaluation/total_metrics_face.csv holding average metrics for the complete head and the facial region respecitively.

Offical Metrics for NPM and NPHM

While training and inference happens in a canonical coordiante system (to be specific we use the coordiante system of FLAME and scale it by a factor of 4), we compute metrics in the metric coordiante system in millimeters (mm).

Quantitative results on the complete head

	ChamferL1(mm)	ChamferL2 (mm)	Normal Consitency	F-Score@1mm	F-Score@5mm
NPM	2.657	35.896	0.883	0.478	0.873
NPHM	2.052	13.714	0.874	0.523	0.902

Quantitative results restricted to the facial area

	ChamferL1(mm)	ChamferL2(mm)	Normal Consitency	F-Score@1mm	F-Score@5mm
NPM	0.657	1.129	0.973	0.840	0.994
NPHM	0.531	0.761	0.976	0.891	0.997

NOTE: The number in the paper are not comparable for 2 reasons. 1: the models were trained on only 87 identities, since all remaining scans wer done afterwards. 2: the metrics are not reported in mm.