View source for LDraw

{{short description|Software for Lego modelling}}
{{Infobox website
| name = LDraw
| favicon = 
| screenshot = LDraw.org.png
| url = {{URL|https://www.ldraw.org/}}
| commercial = No
| registration = Free
| area_served = Worldwide
| owner = LDraw.org
| author = James Jessiman
| launch_date = 
| current_status = Online
| revenue = 
}}
'''LDraw''' is a system of [[freeware]] tools and a [[3D Graphics file format|3D graphics file format]] standard for modeling [[Lego]] creations.

== History ==
The LDraw file format and original program were written by James Jessiman,<ref>{{cite web |title=LDraw.org - File Format 1.0.2 |url=https://www.ldraw.org/article/218.html |access-date=9 July 2019 |work=LDraw.org}}</ref> although the file format has since evolved and extended.<ref>{{Cite web |title=LDraw.org - CATEGORY and KEYWORDS Language Extension |url=https://www.ldraw.org/article/340.html |access-date=2019-07-09 |website=www.ldraw.org}}</ref><ref>{{Cite web |title=LDraw.org - Colour Definition Language Extension |url=https://www.ldraw.org/article/299.html |access-date=2019-07-09 |website=www.ldraw.org}}</ref><ref>{{Cite web |title=LDraw.org - Language Extension for Back Face Culling (BFC) |url=https://www.ldraw.org/article/415.html |access-date=2019-07-09 |website=www.ldraw.org}}</ref><ref>{{Cite web |title=LDraw.org - MPD Language Extension |url=https://www.ldraw.org/article/47.html |access-date=2019-07-09 |website=www.ldraw.org}}</ref><ref>{{Cite web |title=LDraw.org - Official Model Repository (OMR) Specification Version 1.0.3 |url=https://www.ldraw.org/article/593.html |access-date=2019-07-09 |website=www.ldraw.org}}</ref><ref>{{Cite web |title=LDraw.org - Language Extension for Texture Mapping |url=https://www.ldraw.org/documentation/ldraw-org-file-format-standards/language-extension-for-texture-mapping.html |access-date=2019-07-09 |website=www.ldraw.org}}</ref><ref>{{Cite web |title=LDraw.org - Localisation Guideline |url=https://www.ldraw.org/article/559.html |access-date=2019-07-09 |website=www.ldraw.org}}</ref> He also modeled many of the original parts in the parts library, which is under continuous maintenance and extension by the LDraw community.

Following Jessiman's death in 1997,{{sfn|Courtney|Bliss|Herrera|2003|p=396}}<ref>{{cite web |author=OrionP |date=8 November 2003 |title=James Jessiman Memorial |url=https://www.ldraw.org/article/222 |access-date=9 July 2019 |work=LDraw.org |quote=On July 25, 1997, James Jessiman passed away.}}</ref> a variety of programs have been written that use the LDraw parts library, and file format. LDraw models are frequently rendered in [[POV-Ray]] or [[Blender (software)|Blender]], free 3D [[Ray tracing (graphics)|ray tracer]]s.

=== LDraw.org ===
In 2003, ''LDraw.org'' organization has been established, which main task is set to further develop LDraw file format and extend LDraw parts library. Organization is controlled by members of ''LDraw.org Steering Committee'' (''LSC'' for short), elected by users of ''LDraw.org'' forum. Core members of LDraw.org are in close ties with James Jessiman's family, which is the owner of the ''LDraw''™ registered trademark.

=== James Jessiman Memorial Award ===
{{See also|List of web awards}}
{{Infobox award
| name = James Jessiman<br/>Memorial Award
| image = James Jessiman Memorial Award.png
| awarded_for = "Contribution to the furthering of LDraw, the DAT format, and James' memory."<ref name="JJMA">{{cite web|url=https://ldraw.org/article/222.html|title=James Jessiman Memorial Award|publisher=LDraw.org|accessdate=2024-09-01}}</ref>
| country = [[Australia]]
| year = 2009 - Present
| website = {{url|https://ldraw.org/article/222.html|ldraw.org}}
| image2 = LDraw.org.png
}}

Since 2001, LDraw.org project org's awards notable contributors with the James Jessiman Memorial Award.

Recipient is selected by LDraw.org Steering Committee, and approved after a consultation with Jessiman's family.<ref name=":72">{{Cite web |title=LDraw.org - James Jessiman Memorial |url=https://ldraw.org/article/222.html |access-date=2024-09-29 |website=ldraw.org}}</ref>

=== Recipients ===
* 2001 – Steve Bliss
* 2002 – <u>not awarded</u>
* 2003 – Jacob Sparre Andersen
* 2004 – Lars C. Hassing
* 2005 – Michael Lachmann - creator of MLCAD<ref>http://mlcad.lm-software.com</ref>
* 2006 – Orion Pobursky
* 2007 – Kevin Clague
* 2008 – Philippe Hurbain
* 2009 – Tim Courtney
* 2010 – <u>not awarded</u>
* 2011 – Travis Cobbs
* 2012 – Steffen Lohse
* 2013 – Magnus Forsberg
* 2014 – Sergio Reano
* 2015 – Roland Melkert - author of [[LDCad]]<ref>https://www.melkert.net/LDCad</ref>
* 2016 – Nils Schmidt
* 2017 – Chris Dee
* 2018 – Michael 'Mike' Heidemann
* 2019 – Gerald Lasser
* 2020 – Lasse Deleuran
* 2021 – Leonardo Zide,<ref name=":6">{{Cite web |title=Meet Leonardo Zide |url=https://wiki.ldraw.org/wiki/Meet_Leonardo_Zide |access-date=2024-09-29 |website=wiki.ldraw.org}}</ref><ref>{{Cite web |title=Scalable Ambient Obscurance |url=https://research.nvidia.com/publication/2012-06_scalable-ambient-obscurance |access-date=2024-09-30 |website=research.nvidia.com |type=Research}}</ref><ref>{{Cite news |last=McGuire |first=Morgan |last2=Mara |first2=Michael |last3=Luebke |first3=David |date=2012-06-25 |title=Scalable ambient obscurance |url=https://dl.acm.org/doi/abs/10.5555/2383795.2383810 |access-date=30 September 2024 |work=Proceedings of the Fourth ACM SIGGRAPH / Eurographics conference on High-Performance Graphics |publisher=Eurographics Association |pages=97–103 |language=en |isbn=978-3-905674-41-5 |quote=We thank Naty Hoffman (Activision Studio Central), Leonardo Zide (Treyarch), and Louis Bavoil (NVIDIA) for their input on this paper and implementation, [...].}}</ref> [[Software engineering|software engineer]] at [[Treyarch]], author of [[LeoCAD]] (an open-source program for creating virtual Lego models with LDraw).
* 2022 – Takeshi Takahashi
* 2023 – Massimo Maso
* 2024 – Evert-Jan Boer

==File format==
{{Infobox file format
| name          = LDraw
| extensions    = .dat, .ldr, .mpd
| developer     = James Jessiman, LDraw.org
| type          = [[3D computer graphics]], [[text file]]
| standards     = [[Lego]]
| free          = yes
| open          = yes
| url           = {{URL|https://ldraw.org}}
}}
LDraw file format describes "part" (representation of Lego brick) as a set of geometric primitives ("p") in a form of polygonal triangulated mesh.

LDraw "models" consists of LDraw "parts", same way as Lego models consists of Lego bricks.

LDraw file format is plain text file format, and uses [[Comma-separated values|comma-separated]] syntax definition of values.

=== Units ===
[[File:Lego dimensions.svg|thumb|300x300px|Lego brick (real) dimensions]]
[[File:LeoCAD ruler mm.png|thumb|284x284px|Measuring LDraw parts size in [[LeoCAD]] with "ruler" part (ruler tick: 1 mm)]]
'''LDU''' ('''LD'''raw '''U'''nits) — is a base distance unit used in the LDraw format, equals to 1/20 of pin step (distance between centers of 2 closest pins on plate), which in turn almost equals to 0.4 [[millimetre]].
{| class="wikitable" style="text-align: right"
|+Units comparison table
!1&nbsp;= 
!LDU
!mm
!LU
!Flat
!P
!Stud
!Brick
!in
!Comment
|-
|style="text-align:center;|LDU
|style="background:#000000;|
|0.4
|{{frac|1|4}}
|{{frac|1|8}}
|{{frac|1|20}}
|{{frac|1|20}}
|{{frac|1|24}}
|{{frac|1|64}}
|style="text-align:left;|LDraw Unit<ref>{{Cite web|url=https://ldraw.org/article/218|title=LDraw.org - LDraw File Format Specification|website=ldraw.org|access-date=2024-09-25}}</ref><ref>{{Cite web|url=https://philohome.com/calipers/cali.htm|title=LDraw measuring tools|website=philohome.com|access-date=2024-09-25}}</ref><ref>{{Cite web|url=http://studs.sariel.pl|title=LEGO Unit Converter|website=studs.sariel.pl|access-date=2024-09-25}}</ref> — base unit
|-
|style="text-align:center;|mm
|2{{frac|1|2}}
|style="background:#000000;|
|{{frac|5|8}}
|{{frac|5|16}}
|{{frac|1|8}}
|{{frac|1|8}}
|{{frac|7|64}}
|{{frac|3|64}}
|style="text-align:left;|[[millimetre]] = 0.1 [[Centimetre|cm]] = 0.01 [[Decimetre|dm]] = 0.001 [[Metre|m]]
|-
|style="text-align:center;|LU
|4
|1.6
|style="background:#000000;|
|{{frac|1|2}}
|{{frac|1|5}}
|{{frac|1|5}}
|{{frac|1|6}}
|{{frac|1|16}}
|style="text-align:left;|Lego Unit<ref>{{Cite web|url=https://www.designreview.byu.edu/collections/the-lego-brick|title=The LEGO Brick|date=2019-12-18|website=The BYU Design Review|language=en-US|access-date=2024-09-25}}</ref> = 1 p («plastic»<ref>{{Cite web|url=https://brickarchitect.com/scale/|title=LEGO figures in Scale models|last=Alphin|first=Tom|website=BRICK ARCHITECT|language=en-US|access-date=2024-09-25}}</ref>) — thickness of brick wall
|-
|style="text-align:center;|Flat
|8
|3.2
|2
|style="background:#000000;|
|{{frac|2|5}}
|{{frac|2|5}}
|{{frac|1|3}}
|{{frac|1|8}}
|style="text-align:left;|plate height without pin — distance between edges of closest pins
|-
|style="text-align:center;|P
|20
|8.0
|5
|2{{frac|1|2}}
|style="background:#000000;|
|1
|{{frac|5|6}}
|{{frac|5|16}}
|style="text-align:left;|pin step— distance between centers of two closest pins
|-
|style="text-align:center;|Stud
|20
|8.0
|5
|2{{frac|1|2}}
|1
|style="background:#000000;|
|{{frac|5|6}}
|{{frac|5|16}}
|style="text-align:left;|1x1 brick width (real width: P-0.2 mm = 7.8 mm)
|-
|Brick
|24
|9.6
|6
|3
|1{{frac|1|2}}
|1{{frac|1|2}}
|style="background:#000000;|
|{{frac|3|8}}
|style="text-align:left;|brick height without pin
|-
|style="text-align:center;|in
|64
|25.4
|16
|8
|3{{frac|1|5}}
|3{{frac|1|5}}
|3{{frac|1|12}}
|style="background:#000000;|
|style="text-align:left;|[[inch]] = {{frac|1|12}} [[feet]] = {{frac|1|36}} [[yard]]
|-
| colspan="10" style="text-align:left;|'''Notes:''' dimension <code>in</code> and <code>mm</code> are approximated (in <code>mm</code> — rounded to the first decimaldigit)
|}
Some editors (like, [[LeoCAD]]) displaying dimensions and coordinates using only LDU. For measuring and converting sizes from LDU to other units and vice versa, LDraw users created few parts in a form of [[ruler]],<ref>{{Cite web|url=http://www.holly-wood.it/ldraw/helper-en.html|title=Holly-Wood.it > LDraw > Helper parts|website=www.holly-wood.it|access-date=2024-10-03|quote=HlduR.dat (Helper - LDU Ruler).}}</ref> that could be used directly in LDraw editors during visual modeling, that especially useful for [[scale model]] making.

=== Scale ===

LDraw, the same as Lego, uses '''1:42½''' ([[Lego minifigure]] scale) as a base for scaling real world objects for [[scale modeling]]. The precise scale may vary between 1:40 and 1:43.

=== Specification ===

The LDraw format can divide a model into steps so that the building instructions can be incorporated into the design, and also allows for steps that rotate the camera and even move parts around in an elementary fashion. It also allows for models to be incorporated in the construction of larger models to make design easier. This also makes the file format space efficient: instead of specifying the polygons of every single stud of a specific brick for example, a shared stud file is included multiple times with transformation applied.

Parts, models, sub-models and polygons are all treated the same and are not specific to Lego models (only the parts library is). The format could be used to store any type of 3D model. Some have created bricks of other building systems for use with LDraw.

The following main three filename extensions are used by LDraw:{{sfn|Courtney|Bliss|Herrera|2003|p=322}}
* files implementing a part, subpart or primitive use <code>.dat</code>
* a Lego model consisting of 1 or more bricks use <code>.ldr</code>
* multiple <code>.ldr</code> files can be aggregated into files of type <code>.mpd</code>

The file format uses plain text data, and uses the charset [[UTF-8]] without [[byte order mark|BOM]].

=== Example File: 3003.dat, the implementation of a 2 x 2 brick ===

<syntaxhighlight lang="text">0 Brick  2 x  2
0 Name: 3003.dat
0 Author: James Jessiman
0 !LDRAW_ORG Part UPDATE 2002-03
0 !LICENSE Redistributable under CCAL version 2.0 : see CAreadme.txt

0 BFC CERTIFY CCW

0 !HISTORY 2001-10-26 [PTadmin] Official Update 2001-01
0 !HISTORY 2002-05-07 [unknown] BFC Certification
0 !HISTORY 2002-06-11 [PTadmin] Official Update 2002-03
0 !HISTORY 2007-05-07 [PTadmin] Header formatted for Contributor Agreement
0 !HISTORY 2008-07-01 [PTadmin] Official Update 2008-01

1 16 0 4 0 1 0 0 0 -5 0 0 0 1 stud4.dat

0 BFC INVERTNEXT
1 16 0 24 0 16 0 0 0 -20 0 0 0 16 box5.dat

4 16 20 24 20 16 24 16 -16 24 16 -20 24 20
4 16 -20 24 20 -16 24 16 -16 24 -16 -20 24 -20
4 16 -20 24 -20 -16 24 -16 16 24 -16 20 24 -20
4 16 20 24 -20 16 24 -16 16 24 16 20 24 20

1 16 0 24 0 20 0 0 0 -24 0 0 0 20 box5.dat

1 16 10 0 10 1 0 0 0 1 0 0 0 1 stud.dat
1 16 -10 0 10 1 0 0 0 1 0 0 0 1 stud.dat
1 16 10 0 -10 1 0 0 0 1 0 0 0 1 stud.dat
1 16 -10 0 -10 1 0 0 0 1 0 0 0 1 stud.dat
</syntaxhighlight>

The above code defines the basic 2×2 brick. It consists of a five-sided box (''box5.dat'', outside) and an inverted five-sided box (inside), the connection between those two, consisting of four quads (the four lines starting with ''4''), the four studs on top of it (''stud.dat'') and the long hollow stud in the inside (''stud4.dat'').

All lines in an LDraw file are either empty or start with a ''command number'', where 0 means no command (though over time, some lines starting with 0 followed by specific text in capitals also got a meaning as meta commands).{{sfn|Courtney|Bliss|Herrera|2003|pp=152-153}} The command 1 for example includes a subfile. It specifies the file's path and a transformation matrix that should be applied to it, as well as its color (where ''16'' means "use the color that was used when including the current file"). Command 4 specifies a four-sided polygon. There are also commands that define 2D lines. Such lines give the parts a clear contour even in non-shaded orthographic renderings.

=== Example File: pyramid.ldr, a Lego model of a pyramid ===

The following code specifies a simple pyramid model with three layers made of 2 x 4 bricks (brick # 3001)
with changing color and a 2 x 2 brick on top.
<syntaxhighlight lang="text">
0 Example Pyramid for Demonstration of LDRAW Library
0 Name: pyramid.ldr
0 Author: James Jessiman

1 1 -40 -24 60 1 0 0 0 1 0 0 0 1 3001.dat
1 1 40 -24 60 1 0 0 0 1 0 0 0 1 3001.dat
1 1 60 -24 0 0 0 1 0 1 0 -1 0 0 3001.dat
1 1 40 -24 -60 1 0 0 0 1 0 0 0 1 3001.dat
1 1 -40 -24 -60 1 0 0 0 1 0 0 0 1 3001.dat
1 1 -60 -24 0 0 0 1 0 1 0 -1 0 0 3001.dat

0 STEP

1 4 -20 -48 40 1 0 0 0 1 0 0 0 1 3001.dat
1 4 40 -48 20 0 0 1 0 1 0 -1 0 0 3001.dat
1 4 20 -48 -40 1 0 0 0 1 0 0 0 1 3001.dat
1 4 -40 -48 -20 0 0 1 0 1 0 -1 0 0 3001.dat

0 STEP

1 14 0 -72 20 1 0 0 0 1 0 0 0 1 3001.dat
1 14 0 -72 -20 1 0 0 0 1 0 0 0 1 3001.dat

0 STEP

1 0 0 -96 0 1 0 0 0 1 0 0 0 1 3003.dat

0 STEP
</syntaxhighlight>

== Software ==

=== Editors ===

* BlockCAD<ref>https://www.blockcad.net/</ref><ref>{{Cite book |last=Giorgio Musilli |title=I software autore per la didattica: Percorsi creativi nella scuola primaria |date=2014 |publisher=Ledizioni |isbn=978-88-6705-237-0}}</ref><ref>{{Cite journal |date=August 2003 |title=Três programas para as crianças |url=https://datassette.org/softwares/revista-do-cd-rom-br-brasil-cds-de-revistas-diversos-softwares/cd-revista-do-cd-rom-097-0 |journal=Revista do CD-ROM – Informática prática e descomplicada |issue=97 |pages=61 |issn=0104-8732}}</ref>{{sfn|Courtney|Bliss|Herrera|2003|p=392}}<ref>{{Cite book |last=Haylock |first=Derek |title=Understanding mathematics for young children : a guide for teachers of children 3-8 |last2=Cockburn |first2=Anne |publisher=SAGE |year=2013 |isbn=978-1446248669 |edition=4th |page=253 |language=English |quote=This research makes use of the BlockCAD computer program which was designed by Anders Issakson in Sweden and which can be downloaded free. At the time of writing more details were available at blockcad.net}}</ref>
* LDCad
* [[Lego Digital Designer]]
* [[LeoCAD]]
* MLCAD

=== Tools ===

* LDView<ref>https://tcobbs.github.io/ldview/</ref>
* LPub3D<ref>https://trevorsandy.github.io/lpub3d/</ref>

== Other examples ==
<gallery>
File:Lego CAD Racecar.JPG|A racecar created with LDraw
File:Ldraw datsville 01.png|A small town built using the LDraw system of tools and rendered in POV-Ray. The model contains about 250,000 parts.
File:LeoCAD Screenshot with edge lines Flyer from LEGO Masters DK S01E07.png|A flying mechanism that was built in [[Lego Masters|Lego Masters Denmark]] rebuilt in LeoCAD
File:Flyer from LEGO Masters DK S01E07 4K rendering.png|4K rendering of the flying mechanism generated via [[POV-Ray]] render option inside LeoCAD
File:Leocad_Shuttle_Screenshot.png|LeoCAD screenshot of a shuttle model inspired from Endless Sky
File:Spaceship 1.jpg|A spaceship built in LDCad
File:Bricksmith.png|Car viewed using Bricksmith
File:BlockCAD filetypes.png| Supporting LDraw filetype in BlockCAD
</gallery>

== See also ==
* [[Construction set]]
* [[Lego Digital Designer]]

== References ==
{{Reflist}}

== Bibliography ==
* {{cite book |title=Virtual LEGO: The Official LDraw.Org guide to LDraw Tools for Windows |first1=Tim |last1=Courtney |first2=Steve |last2=Bliss |first3=Ahui |last3=Herrera |location=San Francisco |year=2003 |publisher=No Starch Press |isbn=978-1-886411-94-4}}
* {{cite book|title=LEGO Software Power Tools: including LDraw, MLCad, and LPub|first=Kevin|last=Clague|publisher=Syngress|location=Rockland, Mass|year=2002|isbn=978-1-931836-76-0}}

== External links ==
{{Commons and category}}

* {{Official website}}
* [https://brickhub.org/ BrickHub], LDraw-based build library

{{Lego}}

[[Category:Lego]]
[[Category:3D graphics software]]