Editing Workflow:Life Cycle of 3D Data for Cultural Heritage

{{Infobox COW
|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"
|organisationurl=https://3dhumanities.hypotheses.org/
}}
==Workflow Description==


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[[File:GrapheSequetiel_anglais_png.png|400px]]
<br>

<!-- Describe your workflow here with an overview of the different steps or processes involved-->

'''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''<br/>
For example:

{| class="wikitable"
|+ 
|-
! 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''.<br/>
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:
{| class="wikitable"
|+ 
|-
! 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''<br/>
V1n means: v1a, v1b, v1c, ...<br/>
These are the restitution steps or options.It includes humanity knowledge contribution (archaeological, historical, medical, etc.).<br/>
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''<br/>
I concerns the approved options developed in V1n.<br/>
I may be approved by any scientific committee.<br/>
In the best case it is related to a published article.<br/>

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

==Purpose==
<!-- Describe what your workflow is for - i.e. what it is designed to achieve, what the organisational context of the workflow is, and what content it is designed to work with -->
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?<br/>
This workflow defines different steps in the creation of 3D data in humanities and social sciences.<br/>
It identifies how and when 3D data is produced. <br/>
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 ([https://www.huma-num.fr/about-us/ 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.<br/>
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 [[ALTAG3D|aLTAG 3D]]. It leverages the usual complexity of creating metadata and checking the 3D files, so they are suitable for archiving.

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

==Further Information==
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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 [https://hal.archives-ouvertes.fr/hal-03187979 ⟨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⟩