STL Primer

Topic Description

File Extension .stl (ASCII)

.stl (Binary)

Expansion 1 Stereolithography file

Stereolithography Language file (common misnomer)

Standard Triangle Language file (common misnomer)

Standard Triangulation Language file (common misnomer)

Standard Tessellation Language file (common misnomer)

MIME Type 2 model/stl

model/x.stl-ascii

model/x.stl-binary

Structure , , 3 4 5 “The structure of STL Binary, though well defined, makes it impossible to

create an identification signature under the current PRONOM signature

model. The format consists of an 80 byte ASCII header with no formalized

structure, followed by a four byte integer value representing the number of

facets within the file, followed by 48 bytes of floating point values

representing the 'normal' and 'vertex' coordinates within 3 dimensional

space for each triangle, followed by a two byte, typically (but not

exclusively) unused 'attribute byte count’.”

Versions Not Applicable

Primary fields or areas of use This is not a discipline-specific file format, and It can be used by any

field/industry/discipline that involves 3D surface modeling. It is a common

file format in CNC Manufacturing, Architecture, Design, Art History, Biology,

1 Grimm, T. User's Guide to Rapid Prototyping. Dearborn, Mich.: Society of Manufacturing Engineers, 2004, 55. 2 Wikipedia contributors. (2019, July 20). STL (file format). In Wikipedia, The Free Encyclopedia. Retrieved August 9, 2019, from

https://en.wikipedia.org/w/index.php?title=STL_(file_format)&oldid=907075298. 3 National Archives (2016, January 9). Details for: STL (Standard Tessellation Language) Binary. In PRONOM . Retrieved August 9,

2019, from (http://www.nationalarchives.gov.uk/PRONOM/Format/proFormatSearch.aspx?status=detailReport&id=1669. 4 National Archives (2012, March 16). Details for: STL (Standard Tessellation Language) ASCII. In PRONOM . Retrieved August 9,

2019, from http://www.nationalarchives.gov.uk/PRONOM/Format/proFormatSearch.aspx?status=detailReport&id=156 5 Burns, M. (1993). The stl format: standard data format for fabbers. In Automated fabrication: improving productivity in

manufacturing (Section 6.5). Englewood Cliffs, N.J.: Prentice Hall. Retrieved August 9, 2019, from http://www.fabbers.com/tech/STL_Format

This STL Primer document was created as part of the Data Curation Network Training Cohort #2 Workshop and licensed under a Creative Commons Attribution-Noncommercial-Share Alike 4.0 License.

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Chemistry, Engineering, Medicine, Archaeology, etc.

Source and affiliation 6 Originally patented by 3D Systems, Inc. in 1986. Currently a 3D printing de

facto industry standard.

Metadata and cataloging standards Generally field/industry/discipline specific. Examples include: DICOM

(medical), CARARE (archaeology), Audubon Core (biology/ecology),

Community Standards for 3D Data Preservation - CS3DP (forthcoming), etc.

Common Misattributions Standard Template Library (STL) - a software library for the C++

programming language.

Recommended tools for

curation review

Viewing, analyzing, or editing: MeshLab, Blender

Viewing only: GLC Viewer , Microsoft 3D Viewer

(see page 4 for additional information)

Date Created (yyyymmdd) 2019/10/30

Created by Mentor:

Jennifer Moore (j.moore@wustl.edu) Writers:

Elizabeth Blackwood (lzbthblackwood@gmail.com) Doug Joubert (doujou.dc@gmail.com) James Sobczak (james.sobczak@gmail.com)

Date updated (summary of changes) 2020/01/17 (added suggested citation and logo)

Suggested Citation: Blackwood, Elizabeth; Joubert, Doug; Sobczak, James. 2020. STL Data Curation Primer. Retrieved from the University of Minnesota Digital Conservancy. http://hdl.handle.net/11299/211352. This work was created as part of the “Specialized Data Curation” Workshop #2 held at Johns HopkinsUniversity in Baltimore, MD on April 17-18, 2019. These workshops have been generously funded by the Institute of Museum and Library Services # RE-85-18-0040-18. See more primers at https://datacurationnetwork.org/.

Table of Contents

I. Description of format 3

II. Examples of discipline and field specific uses of format 3

III. Examples of STL datasets 3

IV. Software recommendations 4

V. Key curatorial questions 6

VI. Deposit recommendations 6

6 Hull, C. W. (1984). U.S. Patent No. 4,575,330. Washington, DC: U.S. Patent and Trademark Office. Retrieved August 9, 2019, from http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=4,575,330.PN.&OS=PN/4,575,330&RS=PN/4,575,330

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VII. Preservation actions 7

VIII. FAIR principles 8

IX. Unresolved issues / Further questions 8

X. Documentation 8

XI. Additional references / Recommended reading 8

XII. Appendix - STL filetype CURATED checklist 9

I. Description of format

An STL file stores information about 3D models. It is commonly used for printing 3D objects. The STL format

approximates 3D surfaces of a solid model with oriented triangles (facets) of different size and shape (aspect

ratio) in order to achieve a representation suitable for viewing or reproduction using digital fabrication . This 7

format describes only the surface geometry of a three-dimensional object without any representation of color,

texture, or other common model attributes . These files are usually generated as an end product of a 3D 8

modeling or spatial capture process.

II. Examples of discipline and field specific uses of format

STL files are used in a variety of fields that utilize 3D surface modeling, printing, and design. No list could be

exhaustive, though below is a list of some example fields with possible use cases:

● Architecture & Design: modeling/printing building designs

● Art History: modeling/printing art objects for print, study, or exhibition

● Chemistry: modeling/printing molecular models

● Manufacturing: prototyping

● Medical: modeling/printing medical data, objects, organs, etc.

III. Examples of STL datasets Public collections

There are several websites and online exchanges where communities of people can share STL files. Note that the

quality of the digital files, completeness of the metadata, and qualifications/expertise of the uploader can vary

widely. Some examples include:

● Thingiverse: Athena bust from the Altes Museum in Berlin

● NIH 3D Print Exchange: Anti-Morphine Antibody 9B1 Complexed with Morphine

Institutional repositories

● Lam, C. T., Krieger, M. S., Gallagher, J. E., Asma, B., Schmitt, J. W., Ramanujam, N. (2015). Data

from: Design of a novel low cost point of care tampon (POCkeT) colposcope for use in resource

limited settings. Duke Digital Repository. http://hdl.handle.net/10161/10056

● Merck, D., Collins, S., Merck, L., et al. (2016) Ibis mummy CT imaging: [STL files]. Ibis

Mummy CT Imaging, Brown University Open Data Collection, Browniverse: 3D Models

and Printing Digital Library. Brown Digital Repository. Brown University Library.

https://doi.org/10.7301/Z0PZ56R5

7 Rypl, D., & Bittnar, Z. (2006). Generation of computational surface meshes of STL models. Journal of Computational and Applied Mathematics, 192(1), 148-151. Retrieved August 9, 2019, from https://doi.org/10.1016/j.cam.2005.04.054

8 Chakravorty, D. (2019, February 14). STL file format (3d printing) - simply explained. Retrieved August 9, 2019, from https://all3dp.com/what-is-stl-file-format-extension-3d-printing/

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● Reed, M. P., Boyle, K. (2018). Belt fit Manikin Representing a Two-Year-Old Child [Data set]. University of

Michigan Deep Blue Data Repository. https://doi.org/10.7302/Z2BP011N

Scholarly publications using STL files

● Chao, E. Y., Caravella, J. A., Watson, M. A., Campobasso, N., Ghisletti, S., Billin, A. N., . . . Collins, J. L. (2008).

Structure-guided design of N-phenyl tertiary amines as transrepression-selective liver X receptor modulators

with anti-inflammatory activity. J Med Chem, 51(18), 5758-5765. https://doi.org/10.1021/jm800612u

● Conner, B. P., Manogharan, G. P., Martof, A. N., Rodomsky, L. M., Rodomsky, C. M., Jordan, D. C., &

Limperos, J. W. (2014). Making sense of 3-D printing: Creating a map of additive manufacturing products and

services. Additive Manufacturing, 1, 64-76. https://doi.org/10.1016/j.addma.2014.08.005

IV. Software recommendations

Viewers

● GLC Player: (recommended option) A free tool for viewing, navigating, and managing 3D models. (Works

on Mac, Linux, and Windows operating systems. GNU General Public License. )

GLC Player, version 2.20 (windows operating system). To view STL file: File ⟶ Open.

● Microsoft 3D Viewer: (alternate option) Windows 10 app that lets you view 3D models and animations in

real-time. 3D Viewer lets you view 3D models with lighting controls, inspect model data, and visualize

different shading modes. (Works only on Windows operating systems. Proprietary license.)

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Microsoft 3D Viewer (windows operating system). To view STL file: File ⟶ Open.

View, Edit, and Analyze

● MeshLab: (recommended option) A free, open-source tool for opening, viewing, transforming, and

repairing STL files. While it lacks the functionality to create files, it is user-friendly and has a

relatively simple interface. Decent documentation is also available for performing simple tasks.

(Works on Mac, Linux, and Windows operating systems. GNU General Public License.)

MeshLab, version 2016.12 (windows operating system). To view STL file: File ⟶ Import Mesh.

● Blender: (alternate option) A free, open-source tool for professional-level model creation, viewing,

and repairing. While very powerful, this tool has a high learning curve and requires significant

processing abilities to render files and perform actions. It is probably best used for complex files.

There are many online tutorials for understanding and using the software’s robust tools. (Works on

Mac, Linux, and Windows operating systems. GNU General Public License.)

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Blender, version 2.80 (windows operating system). To view STL file: File ⟶ Import ⟶ STL (.stl).

V. Key curatorial questions

To ask yourself

● Given the content of the submission, which repositories are most appropriate/suitable?

○ General repository, domain repository, institutional repository, commercial repository (e.g. Thingiverse

or Sketchfab), etc.

To ask the researcher

● Is this STL file an original design (e.g., a rocket nose cone), a representational model (e.g., a protein

structure), or a real-world documentation (e.g., scan of an antique vase)?

● Can the subject contained within the STL file be described purely in terms of surface-level, geometric data?

○ Does the subject contain additional information related to internal geometry, thickness, color, textual

annotations, lighting, animation, camera views, etc which STL files cannot capture?

● Is this object intended to be reproduced using digital 3D fabrication processes?

○ Is the 3D model complete and contains only manifold geometry (i.e. no gaps, overlapping faces,

disconnected edges/vertices, internal faces, etc.)?

● Was this object originally intended for use in a virtual reality (VR) or augmented reality (AR) environment?

○ What software platform and/or hardware was used in this original viewings/display configuration?

VI. Deposit recommendations

The following outline lists recommendations for repositories accepting STL submissions. Minimally required files

and metadata will support the ability to view and open, but a more comprehensive understanding and use of

the STL file may require additional supporting files, documentation, and/or detailed metadata.

● Minimally required files:

○ .stl file (original file)

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○ .stl file (converted to ASCII encoding)

○ README file (.txt or .md)

– Describing the subject matter of the STL file, the files capture/design process, scale of subject

matter, units of model (e.g. inches, millimeters), list of any transformation/edits taken by the

depositor on behalf of the original author/creator, software used to create the original file

○ LICENSE file (.txt or .md)

– Describing the limitations placed on the STL file in terms of reproduction, reuse, and remixing

● Additional files:

○ Screenshots (.tif format) of the digital model representation generated by the STL file

○ Images (.tif format) of any physical 3D models, prints, or fabrications generated from the STL file

○ Additional documentation related to the STL file’s generation, design, or capture processes

○ List of other products or publications (e.g., URLs, DOI, and/or citations) in which the. STL was used

VII. Preservation actions

● Save a copy of the original STL

● Convert the STL file to ASCII encoding if necessary

○ To check encoding of original STL file, open it using any common text editor (Notepad, TextEdit, etc.)

Same STL file in binary encoding (left) and ASCII encoding (right)

○ Binary to ASCII conversion using MeshLab

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MeshLab, version 2016.12 (windows operating system). To convert binary STL to ASCII STL:

File ⟶ Export Mesh As… ⟶ Select STL as filetype ⟶ Save ⟶ Uncheck Binary Encoding ⟶ OK

VIII. FAIR principles 9

● To be Findable:

○ F1. metadata are assigned a globally unique and persistent identifier (e.g., DOI)

○ F2. STL is described with rich metadata

○ F3. metadata clearly and explicitly include the identifier of the data it describes

○ F4. metadata are registered or indexed in a searchable resource

● To be Accessible:

○ A1. metadata are retrievable by their identifier using a standardized communications protocol

○ A2. metadata are accessible, even when the STL is no longer available

● To be Interoperable:

○ I1. metadata use a formal, accessible, shared, and broadly applicable language

○ I2. metadata use vocabularies that follow FAIR principles

○ I3. metadata include qualified references to other metadata

● To be Reusable:

9 Wilkinson, M. D., et al. (2016). The FAIR Guiding Principles for scientific data management and stewardship. Scientific Data, 3(1), 160018. Retrieved August 9, 2019, from https://doi.org/10.1038/sdata.2016.18.

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○ R1. metadata are richly described with a plurality of accurate and relevant attributes including usage

license, provenance, and domain-relevant community standards

IX. Unresolved issues / Further questions

● How to track future reuse/remixes of STL file?

● Repository platforms may not accommodate non-textual information (e.g. preview image viewers, 3D model

viewers, etc.)

X. Documentation

Documentation of the curation process should capture:

● Software used for viewing, analyzing, or editing the STL file

● Communications, discussions, or questions raised during the curation process between the uploader and

researcher/creator

● Metadata added by researcher and/or creator

● Transformations of the STL file taken by the uploader or researcher/creator

XI. Additional references / Recommended reading

Chakravorty, Dibya. “STL File Format (3D Printing) – Simply Explained.” All3DP, 14 Feb. 2019. Retrieved August 9,

2019, from https://all3dp.com/what-is-stl-file-format-extension-3d-printing/. Fino-Radin, Ben. “Preserving 3D Data and 3D Prints: Cooper Hewitt, Smithsonian Design Museum.” Cooper

Hewitt Smithsonian Design Museum, 14 May 2019. Retrieved August 9, 2019, from

https://www.cooperhewitt.org/2019/05/14/preserving-3d-data-and-3d-prints/. Henri, Janine. “Describing 3D Models: Thesauri, Controlled Vocabularies, and Metadata Standards.” UCLA

Library, 24 April 2019.Retrieved August 9, 2019, from https://guides.library.ucla.edu/3D.

XII. Appendix - STL filetype CURATED checklist

CHECK Step

CURATE Action Curator Checklist

Check STL files and read documentation

● Review the file.

● Verify all metadata provided by the

author and review the available

documentation.

STL file opens as expected

❏ Yes

❏ No, issues: ________________________________

Metadata quality is rich, accurate, and complete

❏ Yes

❏ No, issues: ________________________________

Documentation is rich, accurate, and complete

❏ Yes

❏ No, issues: ________________________________

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UNDERSTAND Step

CURATE Action Curator Checklist

Understand the STL file

● Check for quality assurance and usability

issues

● Try to detect and extract any “hidden

documentation” inherent to the STL file

that may facilitate reuse.

● Determine if the documentation of the

data is sufficient for a user with similar

qualifications to the author’s to

understand and reuse the data. If not,

recommend or create additional

documentation.

Subject matter can be sufficiently represented with only 3D

surface-level geometry

❏ Yes

❏ No, recommend alternative file format (e.g., OBJ, X3D)

alternative format used:_____________________

Scale and model units included

❏ Yes

❏ No, issues: ________________________________

Method of creation/capture is clearly

❏ Yes

❏ No, issues: ________________________________

REQUEST Step

CURATE Action Curator Checklist

Request missing information or changes

● Generate a list of questions for the STL

file author to fix any errors or issues.

Narrative describing the concerns, issues, and needed

improvements to the data submission

❏ Inquiry sent to researcher

❏ Response received

❏ Additional follow up communication needed

AUGMENT Step

CURATE Action Curator Checklist

Augment the submission

● Enhance metadata to best facilitate

discoverability.

● Create and apply metadata for the STL

file record, including descriptive

keywords.

● When appropriate, structure and

present metadata in domain-specific

schemas to facilitate interoperability

with other systems.

Discoverability sufficient

❏ Yes

❏ No, recommend (circle one) full-text index / file rename /

file reorder / file descriptions / archive zip / other actions:

_________________________________________

Keywords Sufficient

❏ Yes

❏ No, suggestions:

__________________________________________

Linkages Sufficient

❏ Yes

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❏ No, links to reports/papers/publications/data sets:

__________________________________________

TRANSFORM Step

CURATE Action Curator Checklist

Transform file formats

● Identify specialized file formats and

their restrictions (e.g., Is the software

freely available? Link to it or archive it

alongside the data).

● Transform files into open,

non-proprietary file formats that

broaden the potential audience for

reuse and ensure that preservation

actions might be taken by the repository

in later steps.

● Retain original files

Preferred STL file encoding (ASCII) in use

❏ Yes

❏ No, conversion required

Original file present and retained

❏ Yes

❏ No

2D images, visualizations, screenshots, or representations of

the 3D STL file are included and previewable

❏ Yes

❏ No

EVALUATE Step

CURATE Action Curator Checklist

Evaluate and rate the overall data record for

FAIRness.*

● Score the file and metadata and

recommend ways to increase the

FAIRness of the data and become “DCN

approved.”

Findable

❏ Metadata exceeds author/title/date

❏ Unique PID (e.g., DOI, Handle, PURL, etc.)

❏ Discoverable via web search engines

Accessible

❏ Retrievable via a standard protocol (e.g., HTTP)

❏ Free, open (e.g., download link)

Interoperable

❏ Metadata formatted in a standard schema

(e.g., Dublin Core)

❏ Metadata provided in machine-readable format

(e.g., OAI feed)

Reusable

❏ Data include sufficient metadata about the data

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* Rubric evaluating the FAIR principles are based on the scoring

matrix by Dunning, de Smaele, & Böhmer (2017).

characteristics to reuse

❏ Contact info displayed if the direct assistance of the

author/creator needed

❏ Clear indicators of who created, owns, and stewards the

file in the future

❏ Data are released with clear data usage terms

(e.g., a CC License)

DOCUMENT Step

CURATE Action Curator Checklist

Document throughout curation activities.

● Record all necessary information

capturing who did what to the

dataset and when

❏ Accessioning & deposit records (names, dates, contact

information, submission agreements, etc)

❏ Repository collection metadata

❏ Provenance logs (tracking any changes/edit to the STL

file’s geometry or encoding)

❏ Service workflow

❏ Preservation packaging

❏ Include information regarding any additional repository

or record requirements at your institution

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