Workflow:Life Cycle of 3D Data for Cultural Heritage

Life Cycle of 3D Data for Cultural Heritage
Status:	Production
Input:	As inputs, we take all documents from any formats and raw acquired data that will be used to create a digital 3D restitution of an object from Cultural Heritage.
Output:	The ouput of this workflow are scientifically validated 3D data.
Organisation:	Consortium "3D for Humanities"

Workflow Description

The steps are:

• A0: raw acquired data
• V0: processed data
• V1n: hypotheses and restitutions loops and options
• V2: approved restitutions

Each step may be archived independently. The AIP should be properly linked.All steps may be gathered in a single archive.

A0 - Raw data - Archived

A0 = raw acquired data
For example:

Process	Data	File type
Photogrammetry	2D color pictures	tiff, dng, ...
Lasergrammetry	point-cloud	ply ASCII, ...
Tomography	shades of grey 2D picture+ descriptions	ANALYZE (hdr + img), DICOM
Archives / historical sources	2D pictures, texts, sound, 3D ...	png, jpg, pdf, ogg, ply,
Other	GPS data, color calibration target, acquisition process	txt

These data are the most important to archived. They are the primary sources and the condition for the data to be re-used (i.e. the purpose of an archive).

V0 - Processed data - Archived

V0 = A0 + basic human action + software process.
This is the first 3D technically validated by a human.

It may have been:

• cleaned
• assembled
• meshed
• holes filled
• textured with acquired 2D images

For example:

Process	VO
Photogrammetry	mesh or the point-cloud based on the pictures only.With human choices for parameters and manual cleaning, selecting points, georeferecencing, etc.
Lasergrammetry	cleaned point-cloud, meshed, georeferenced, etc.
Tomography	-
Archives / historical sources	V0 doesn’t exist

These data are archived, because they are the basis of the humanity work.

V1n - Restitutions - NOT archived

V1n = v0 + human knowledge
V1n means: v1a, v1b, v1c, ...
These are the restitution steps or options.It includes humanity knowledge contribution (archaeological, historical, medical, etc.).
They are working data, options and trials. These loops express the recursive aspect of the work with hypothesis and restitution stages.

It may have been:

• semantically enriched
• completed (missing parts)
• animated

These data are not archived because they are work-in-progress files.

V2 - Approved restitutions - Archived

V2 = scientifically approved V1n
I concerns the approved options developed in V1n.
I may be approved by any scientific committee.
In the best case it is related to a published article.

These data are archived because they show the outcome of the project.

Purpose

It presents the steps of the production process in a simplified way. The system of the graph has been defined to follow a logical path with notably the use of loops to express the recursive aspect of the work on data, especially during the hypothesis and restitution stages.

In a 3D restitution process: which data may be archived?
This workflow defines different steps in the creation of 3D data in humanities and social sciences.
It identifies how and when 3D data is produced.
It chooses 3D data for archiving.

Context

3D is now commonly used for Cultural Heritage study, valorization and preservation. The gathered experiences make possible to define standard processes and practices to ensure data quality and their preservation. Under the supervision of the French national infrastructure for digital humanities (Huma-Num), the Consortium "3D for Humanities" has thus defined a life cycle of such data from creation up to archiving.

It was part of its missions that are:

• bring together groups working in the field of archaeology or cultural heritage, using 3D technologies and producing 3D models;
• define the vocabulary associated with 3D technologies for HSS;
• develop specific open-source 3D tools;
• disseminate good practices and commissioning a conservatory dedicated to 3D data.

This 3D life cycle was initially designed for archaeology, and is now open to any humanity field.

Content

This workflow is designed to stage 3D data from raw acquired data to restitution.

We have formalized the different steps of data life Cycle.

• The first stage consists in collecting data production from capture device (laser scanner, digital camera…). These data are A0.
• The second stage consists in processing the data (cleaning, meshing,…). It creates the initial 3D models V0.
• The third stage consists in the humanity work. It results in many new 3D modeling and hypotheses. This step may be looped creating V1n versions
• The last stage consists in receiving scientific approval for the selected V1. Approved V1n are called V2. They are the final versions from the humanity point of view.

A additional rendering stage may be considered when public communication and dissemination is carried out.

A0, V0 and all version of V2 are candidates for archiving.
We have formalized this process with a sequential graph.

Additionally to these conceptual stages, there hare been developed

• a metadata schema dedicated to the long-term archiving of 3D models for HSS
• a software aLTAG 3D. It leverages the usual complexity of creating metadata and checking the 3D files, so they are suitable for archiving.

Evaluation/Review

The workflow is a consensus applied in all team of the french consortium for 3D. The teams are mainly focused on heritage objects.
It is being updated to work with fields of humanities others than cultural heritage.

Further Information

Xavier Granier, Laurent Bergerot, Mehdi Chayani, Bruno Dutailly, Pascal Mora, et al. 3D lexicon for Human and Social Sciences. Recommendations of the "Consortium 3D for Humanities", 2021. p 6 ⟨hal-03187979⟩

Bruno Dutailly, Sylvie Eusèbe, Valentin Grimaud, Nicolas Lefèvre, Mathieu Quantin, et al.. Life cycle of 3d data for cultural heritage: Identify how and when 3D data is produced. Choose 3D file formats for archiving. Define a robust process for producing 3D data and preserving it. Visual Heritage 2018, Nov 2018, Vienne, Austria. ⟨hal-01926434⟩