Multi-View Optimization of Local Feature Geometry

This repository contains the implementation of the following paper:

"Multi-View Optimization of Local Feature Geometry".
M. Dusmanu, J.L. Schönberger, and M. Pollefeys. European Conference on Computer Vision 2020 (Oral).

[Paper on arXiv] [Project page] [Qualitative results]

Requirements

C++

COLMAP should be installed as a library before proceeding. Please refer to the official website for installation instructions. For the paper, we have used the dev branch of COLMAP at commit f4eaade (you can run git checkout f4eaade before compiling COLMAP to use the same version). We recommend setting an environmental variable to the colmap folder by running COLMAP_PATH=path_to_colmap_executable_folder.

The only additional requirement is protobuf which can be installed on Ubuntu as follows sudo apt install protobuf-compiler libprotobuf-dev.

Start by parsing the proto file and generate output for both Python and C++:

protoc --python_out=two-view-refinement/ --python_out=reconstruction-scripts/ --cpp_out=multi-view-refinement/ types.proto

Now, the multi-view refinement code can be compiled as follows:

cd multi-view-refinement
mkdir build; cd build
cmake ..
make

Python

Python 3.6+ is recommended for running our code. Conda can be used to create a new environment and install the required packages:

conda create -n local-feature-refinement -y
conda activate local-feature-refinement

conda install pytorch torchvision cudatoolkit=10.1 -c pytorch -y
conda install opencv imagesize tqdm protobuf -c conda-forge -y

Extracting features

Click for details...

In order to make our evaluation reproducible regardless of updates to the repositories of individual features, we have forked all repositories at the point in time when we evaluated them. Please refer to the individual repositories for installation instructions.

SIFT

We used the GPU-SIFT distribution coming with COLMAP. You can use the following command to extract features:

python utils/extract_features_sift.py --colmap_path $COLMAP_PATH --image_path path_to_images

SURF

We used the OpenCV implementation. You can use the following command to extract features:

python utils/extract_features_surf.py --image_path path_to_images

D2-Net

Clone the repository (git clone [email protected]:mihaidusmanu/d2-net.git; git checkout 2a4d88f) and use the following command to extract features:

python extract_features.py --image_list_file image_list.txt (--multiscale)

Key.Net

Clone the fork (git clone [email protected]:mihaidusmanu/Key.Net.git; git checkout local-feature-refinement) and use the following command to extract features:

python extract_multiscale_features.py --list_images image_list.txt

R2D2

Clone the fork (git clone [email protected]:mihaidusmanu/r2d2.git) and use the following command to extract features:

python extract.py --images image_list.txt

SuperPoint

Clone the fork (git clone [email protected]:mihaidusmanu/SuperPointPretrainedNetwork.git) and use the following command to extract features:

python extract_features_superpoint_list.py image_list.txt

Image lists

To create the image lists, you can use the provided utility utils/create_image_list_file.py.

Running the Local Feature Evaluation Benchmark

Click for details...

Once the multi-view refinement code was compiled successfully, the environment was created, and you made sure that you can run feature extraction, you can try out the Local Feature Evaluation Benchmark. To make sure that everything is working properly, we recommend starting on the two small datasets (Fountain and Herzjesu). You can download the datasets by running bash local-feature-evaluation/download.sh (~4GB required).

The evaluation can be run using the following command:

python local-feature-evaluation/benchmark.py --colmap_path $COLMAP_PATH --dataset_name dataset_name --method_name method_name

For instance, in order to evaluate SIFT on Fountain, one would run:

python local-feature-evaluation/benchmark.py --colmap_path $COLMAP_PATH --dataset_name Fountain --method_name sift

This will produce two output files: output/sift-Fountain-ref.txt and output/sift-Fountain-raw.txt containing json objects with reconstruction statistics for features with and without refinement, respectively.

Similarly to the paper, local-feature-evaluation/compare_reconstructions.py can be used to compare a refined reconstruction and its raw counterpart on commonly registered images only.

Running the ETH3D Triangulation Benchmark

Click for details...

You can download and prepare the dataset by running bash eth/download.sh; bash eth/prepare_dataset.sh $COLMAP_PATH (~15GB required). Please follow the official instructions to install the ETH3D multi-view evaluation program. We recommend setting an environmental variable to the evaluation folder by running EVAL_PATH=path_to_evaluation_executable_folder.

The evaluation can be run using the following command:

python eth/benchmark.py --colmap_path $COLMAP_PATH --evaluation_path $EVAL_PATH --dataset_name dataset_name --method_name method_name

For instance, in order to evaluate SIFT on pipes, one would run:

python eth/benchmark.py --colmap_path $COLMAP_PATH --evaluation_path $EVAL_PATH --dataset_name pipes --method_name sift

This will produce two output files: output/sift-pipes-ref.txt and output/sift-pipes-raw.txt containing sparse triangulation accuracy and completeness for features with and without refinement, respectively.

Running in a custom scenario

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Custom dataset

In order to facilitate the use of our method with custom datasets, we provide several helpful scripts:

• utils/create_starting_database.py creates an initial database containing images and camera information from EXIF data.
• utils/create_image_list_file.py creates a list of images image-list.txt from a database.
• utils/create_exhaustive_matching_file.py creates an exhaustive list of image pairs to match match-list.txt from a database.

Custom features

The proposed method works regardless of local features used. You can provide your own features in npz files that encapsulate two arrays:

• keypoints - N x 2 - array containing the positions of keypoints x, y. The X axis is pointing to the right and the Y axis to the bottom.
• descriptors - N x D - array containing the L2 normalized descriptors.

Reconstruction

We suppose the dataset directory has the following structure:

.
├── images
│  └── *.{jpg | png | ...}
│  └── *.{jpg | png | ...}.method_name (npz files with features)
├── database.db (created by utils/create_starting_database.py)
├── image-list.txt (created by utils/create_image_list_file.py)
└── match-list.txt (created by utils/create_exhaustive_matching_file.py for instance)

The list of image pairs to match match-list.txt can be replaced by a partial list. For image datasets extracted from videos, you can use sequential matching (i.e, last 10-20 frames). For large datasets (>100 images), we suggest using retrieval first and only matching with respect to the closest 20-50 images.

To run the refinement pipeline followed by 3D reconstruction with both refined and raw features, you can use:

python custom_demo.py --colmap_path $COLMAP_PATH --dataset_name dataset_name --dataset_path path_to_dataset --method_name method_name

The output is the same as for the Local Feature Evaluation Benchmark. You can then use COLMAP to visualize the resulting reconstructions.

If you are using a method that's not part of our initial evaluation, don't forget to add the feature extraction resolution and matching parameters to max_size_dict and matcher_dict respectively at the top of custom_demo.py.

Benchmarking new methods without refinement

The two-view refinement can be skipped completely by setting the following environmental variable SKIP_REFINEMENT=1. For instance, in order to evaluate SIFT without refinement on pipes, one would run:

SKIP_REFINEMENT=1 python eth/benchmark.py --colmap_path $COLMAP_PATH --evaluation_path $EVAL_PATH --dataset_name pipes --method_name sift

Coming soon

This repository will be updated during the following months with

• Local Feature Evaluation benchmark code and instructions
• HPatches Sequences matching evaluation code and instructions
• ETH3D triangulation evaluation code and instructions
• ETH3D localization evaluation code and instructions
• Training data and scripts

BibTeX

If you use this code in your project, please cite the following paper:

@InProceedings{Dusmanu2020Multi,
    author = {Dusmanu, Mihai and Sch\"onberger, Johannes L. and Pollefeys, Marc},
    title = {{Multi-View Optimization of Local Feature Geometry}},
    booktitle = {Proceedings of the European Conference on Computer Vision},
    year = {2020},
}