PySfMUtils 1.0.0

A Python library for interacting with Structure-from-Motion projects

PySfMUtils

A Python package for interacting with Structure-from-Motion (SfM) projects.

Requirements

• Python 3.6+
• numpy 1.15+

Installation

The package is registered on PyPI. Released versions can be installed using pip:

pip install PySfMUtils

Development versions can be installed directly from the GitHub repository:

python -m pip install -e git+https://github.com/viscenter/sfm-utils.git

Usage

This package was originally designed to ease the process of importing pose priors into OpenMVG. It contains a format agnostic interface for defining an SfM Scene and its component parts:

import sfm_utils as sfm

# Create the scene
scene = sfm.Scene()
scene.root_dir = '/path/to/images/'

# Construct a view
view = sfm.View()
view.path = "view.jpg"
view.width = 800
view.height = 600
view.camera_make = 'PySfMUtils'
view.camera_model = 'Test Camera'
scene.add_view(view)

# Add the view's intrinsics
intrinsic = sfm.IntrinsicRadialK3()
intrinsic.width = view.width
intrinsic.height = view.height
intrinsic.focal_length = 50
intrinsic.sensor_width = 36
intrinsic.dist_params = [-0.1, -1.1, -1.1]
view.intrinsic = scene.add_intrinsic(intrinsic)

# Add the view's pose
pose = sfm.Pose()
pose.center = [10, 10, 10]
view.pose = scene.add_pose(pose)

# Write an OpenMVG project file
sfm.export_scene(path='sfm_data.json', scene=scene)

The exported sfm_data.json file can be passed directly to OpenMVG programs:

openMVG_main_ComputeFeatures -i sfm_data.json -o matches/

Export to AliceVision/Meshroom

To export a scene to an AliceVision/Meshroom compatible json file, use sfm_utils.export_scene:

import sfm_utils as sfm
scene = sfm.Scene()
...
sfm.export_scene(path='SfMData.json', scene=scene, fmt=sfm.Format.ALICE_VISION)

The AliceVision json file matches an example file generated by Meshroom, but has not been tested for actually performing reconstructions. Contributions to this functionality are welcome.

Limitations

This package is a work-in-progress and currently implements only the most basic features needed to import pre-calibrated camera pose information into OpenMVG. We will gladly accept pull requests for new features. Known limitations in the current implementation are as follows:

• Only Views, Poses, and Intrinsics are supported. Feature points, control points, tracks, etc. are not provided.
• Only the Pinhole, RadialK3, and BrownT2 camera intrinsics are implemented.
• AliceVision support is untested.
• There is no support for loading pre-existing SfM files.

A Note on Camera Rotations

This package assumes a right-handed coordinate system, in contrast to the left-handed system used by OpenMVG. When exporting to OpenMVG, this package will automatically compose the Pose.rotation matrix with the following matrix:

-1,  0,  0
 0,  1,  0
 0,  0, -1