Wikipedia

LDraw

LDraw is a system of freeware tools and a 3D graphics file format standard for modeling Lego creations.

LDraw
Area servedWorldwide
OwnerLDraw.org
Created byJames Jessiman
URLhttps://www.ldraw.org/ Edit this at Wikidata
CommercialNo
RegistrationFree
Current statusOnline

History

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The LDraw file format and original program were written by James Jessiman,[1] although the file format has since evolved and extended.[2][3][4][5][6][7][8] 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,[9][10] 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, free 3D ray tracers.

LDraw.org

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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 Commitee (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

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See also: List of web awards
James Jessiman
Memorial Award
 
Awarded for"Contribution to the furthering of LDraw, the DAT format, and James' memory."[11]
CountryAustralia
First awarded2009 - Present
Websiteldraw.org
 

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.[12]

Recipients

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  • 2001 - Steve Bliss
  • 2002 - not awarded
  • 2003 - Jacob Sparre Andersen
  • 2004 - Lars C. Hassing
  • 2005 - Michael Lachmann
  • 2006 - Orion Pobursky
  • 2007 - Kevin Clague
  • 2008 - Philippe Hurbain
  • 2009 - Tim Courtney
  • 2010 - not awarded
  • 2011 - Travis Cobbs
  • 2012 - Steffen Lohse
  • 2013 - Magnus Forsberg
  • 2014 - Sergio Reano
  • 2015 - Roland Melkert
  • 2016 - Nils Schmidt
  • 2017 - Chris Dee
  • 2018 - Michael 'Mike' Heidemann
  • 2019 - Gerald Lasser
  • 2020 - Lasse Deleuran
  • 2021 - Leonardo Zide,[13][14][15] software engineer at Treyarch, author of LeoCAD (an open-source program for creatiing virtual Lego models with LDraw).
  • 2022 - Takeshi Takahashi
  • 2023 - Massimo Maso

File format

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LDraw
Filename extensions
.dat, .ldr, .mpd
Developed byJames Jessiman, LDraw.org
Type of format3D computer graphics, text file
StandardsLego
Open format?yes
Free format?yes
Websiteldraw.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 syntax definition of values.

Units

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Lego brick (real) dimensions
 
Measuring LDraw parts size in LeoCAD with "ruler" part (ruler tick: 1 mm)

LDU (LDraw Units) — 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.

Units comparison table
1 = LDU mm LU Flat P Stud Brick in Comment
LDU 0.4 1⁄4 1⁄8 1⁄20 1⁄20 1⁄24 1⁄64 LDraw Unit[16][17][18] — base unit
mm 21⁄2 5⁄8 5⁄16 1⁄8 1⁄8 7⁄64 3⁄64 millimetre = 0.1 cm = 0.01 dm = 0.001 m
LU 4 1.6 1⁄2 1⁄5 1⁄5 1⁄6 1⁄16 Lego Unit[19] = 1 p («plastic»[20]) — thickness of brick wall
Flat 8 3.2 2 2⁄5 2⁄5 1⁄3 1⁄8 plate height without pin — distance between edges of closest pins
P 20 8.0 5 21⁄2 1 5⁄6 5⁄16 pin step— distance between centers of two closest pins
Stud 20 8.0 5 21⁄2 1 5⁄6 5⁄16 1x1 brick width (real width: P-0.2 mm = 7.8 mm)
Brick 24 9.6 6 3 11⁄2 11⁄2 3⁄8 brick height without pin
in 64 25.4 16 8 31⁄5 31⁄5 31⁄12 inch = 1⁄12 feet = 1⁄36 yard
Notes: dimension in and mm are approximated (in mm — rounded to the first decimaldigit)

Some editrs (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,[21] that could be used directly in LDraw editors during visual modeling, that especially useful for scale model making.

Scale

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LDraw, same as Lego, uses 1:42½ (Lego minifigure scale) as base for scaling real world object for scale modeling. Its may drift between 1:40 to 1:43, which are popular among other interests.

Specification

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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:[22]

  • files implementing a part, subpart or primitive use .dat
  • a Lego model consisting of 1 or more bricks use .ldr
  • multiple .ldr files can be aggregated into files of type .mpd

The file format uses plain text data, and uses the charset UTF-8 without BOM.

Example File: 3003.dat, the Implementation of a 2 x 2 Brick

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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

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).[23] 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

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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. 

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

Other examples

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  •  
    A racecar created with LDraw
  •  
    A small town built using the LDraw system of tools and rendered in POV-Ray. The model contains about 250,000 parts.
  •  
    A spaceship created in LDCad
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    Car viewed using Bricksmith

See also

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References

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  1. ^ "LDraw.org - File Format 1.0.2". LDraw.org. Retrieved 9 July 2019.
  2. ^ "LDraw.org - CATEGORY and KEYWORDS Language Extension". www.ldraw.org. Retrieved 2019-07-09.
  3. ^ "LDraw.org - Colour Definition Language Extension". www.ldraw.org. Retrieved 2019-07-09.
  4. ^ "LDraw.org - Language Extension for Back Face Culling (BFC)". www.ldraw.org. Retrieved 2019-07-09.
  5. ^ "LDraw.org - MPD Language Extension". www.ldraw.org. Retrieved 2019-07-09.
  6. ^ "LDraw.org - Official Model Repository (OMR) Specification Version 1.0.3". www.ldraw.org. Retrieved 2019-07-09.
  7. ^ "LDraw.org - Language Extension for Texture Mapping". www.ldraw.org. Retrieved 2019-07-09.
  8. ^ "LDraw.org - Localisation Guideline". www.ldraw.org. Retrieved 2019-07-09.
  9. ^ Courtney, Bliss & Herrera 2003, p. 396.
  10. ^ OrionP (8 November 2003). "James Jessiman Memorial". LDraw.org. Retrieved 9 July 2019. On July 25, 1997, James Jessiman passed away.
  11. ^ "James Jessiman Memorial Award". LDraw.org. Retrieved 2024-09-01.
  12. ^ "LDraw.org - James Jessiman Memorial". ldraw.org. Retrieved 2024-09-29.
  13. ^ "Meet Leonardo Zide". wiki.ldraw.org. Retrieved 2024-09-29.
  14. ^ "Scalable Ambient Obscurance". research.nvidia.com (Research). Retrieved 2024-09-30.
  15. ^ McGuire, Morgan; Mara, Michael; Luebke, David (2012-06-25). "Scalable ambient obscurance". Proceedings of the Fourth ACM SIGGRAPH / Eurographics conference on High-Performance Graphics. Eurographics Association. pp. 97–103. ISBN 978-3-905674-41-5. Retrieved 30 September 2024. We thank Naty Hoffman (Activision Studio Central), Leonardo Zide (Treyarch), and Louis Bavoil (NVIDIA) for their input on this paper and implementation, [...].
  16. ^ "LDraw.org - LDraw File Format Specification". ldraw.org. Retrieved 2024-09-25.
  17. ^ "LDraw measuring tools". philohome.com. Retrieved 2024-09-25.
  18. ^ "LEGO Unit Converter". studs.sariel.pl. Retrieved 2024-09-25.
  19. ^ "The LEGO Brick". The BYU Design Review. 2019-12-18. Retrieved 2024-09-25.
  20. ^ Alphin, Tom. "LEGO figures in Scale models". BRICK ARCHITECT. Retrieved 2024-09-25.
  21. ^ "Holly-Wood.it > LDraw > Helper parts". www.holly-wood.it. Retrieved 2024-10-03. HlduR.dat (Helper - LDU Ruler).
  22. ^ Courtney, Bliss & Herrera 2003, p. 322.
  23. ^ Courtney, Bliss & Herrera 2003, pp. 152–153.

Further reading

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  • Courtney, Tim; Bliss, Steve; Herrera, Ahui (2003). Virtual LEGO: The Official LDraw.Org guide to LDraw Tools for Windows. San Francisco: No Starch Press. ISBN 978-1-886411-94-4.
  • Clague, Kevin (2002). LEGO Software Power Tools: including LDraw, MLCad, and LPub. Rockland, Mass: Syngress. ISBN 978-1-931836-76-0.
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