Documentation: Multi-Part Document (MPD) Language Extension

Maintained by: LDraw.org Standards Board
Revision: Revision: 2, 26-May-2020

Revision History:
Revision 1: Original
Revision 2: Added !DATA meta

This is an ratified, official LDraw.org document. Non-adminstrative changes can only be made with the approval of the maintainer.

Purpose

MPD files or "Multi-Part Documents" are a way to combine several LDraw and encoded binary files into one consolidated source. This allows for ease in posting or emailing a model made up of many subparts.

Structure

A MPD file consists out of blocks of LDraw code separated by 0 FILE or 0 !DATA statements. Each block is considered a separate file and can be referenced by the other ones as needed.

Blocks starting with the 0 FILE statement are normal type 0..5 line LDraw code.

Blocks starting with the 0 !DATA statement contain binary data encoded using a multitude of 0 !: lines. Each of those lines contain a chunk of base64 encoded data which a parser must combine before decoding. No other LDraw statements may be used inside a !DATA block.

The end of each block, or just the last block in the MPD, may be marked with a 0 NOFILE line. The 0 NOFILE command is only required if the file's contents are followed by non-LDraw content (such as the poster's signature lines). LDraw parsers must then ignore all content until a new 0 FILE or 0 !DATA is found.

In order to support the inclusion of MPD files in message systems (like email), any text lines before the first 0 FILE or 0 !DATA statement will be discarded. It is considered to be an error for any LDraw code (other than comment lines) to appear before the first 0 FILE or 0 !DATA statement.

The first block in the MPD is treated as the 'main model' -- all other files in the MPD will only be rendered if they are referenced by the main model, directly or indirectly. For this reason it is recommended (but not required) to always use a 0 FILE block as the first entry in the MPD.

So far, there are no clear scoping or namespace rules on MPD files. If you put a file named stud.dat in your MPD file, don't be surprised to see your stud.dat file appear on the top of every single brick in your scene.

MPD META Statements

FILE
Format: 0 FILE <filename>
Where:
<filename> is the name of the following LDraw file.

!DATA
Format: 0 !DATA <filename>
Where:
<filename> is the filename of the following encoded data.

!:
Format: 0 !: <base64 string>
Where:
<base64 string> is a chunk of the base64 encoded data (A-Za-z0-9+/) with a maximum length of 80 characters (60 bytes of data). Each line except the last should use the same length and be a multiple of 4 characters. Padding the last line with '=' characters to complete its last group of 4 is optional.

NOFILE
Format: 0 NOFILE
There are no options or parameters.

Example

0 FILE main.ldr
1 7 0 0 0 1 0 0 0 1 0 0 0 1 819.dat
1 4 80 -8 70 1 0 0 0 1 0 0 0 1 house.ldr
1 4 -70 -8 20 0 0 -1 0 1 0 1 0 0 house.ldr
1 4 50 -8 -20 0 0 -1 0 1 0 1 0 0 house.ldr
1 4 0 -8 -30 1 0 0 0 1 0 0 0 1 house.ldr
1 4 -20 -8 70 1 0 0 0 1 0 0 0 1 house.ldr

0 FILE house.ldr
1 16 0 0 0 1 0 0 0 1 0 0 0 1 3023.dat
1 16 0 -24 0 1 0 0 0 1 0 0 0 1 3065.dat
1 16 0 -48 0 1 0 0 0 1 0 0 0 1 3065.dat
1 16 0 -72 0 0 0 -1 0 1 0 1 0 0 3044b.dat
1 4 0 -22 -10 1 0 0 0 0 -1 0 1 0 sticker.ldr

0 FILE sticker.ldr
0 UNOFFICIAL PART
0 BFC CERTIFY CCW
1 16   0 -0.25 0   20 0 0   0 0.25 0   0 0 30   box5.dat
0 !TEXMAP START PLANAR   -20 -0.25 30   20 -0.25 30   -20 -0.25 -30   sticker.png
4 16   -20 -0.25 30   -20 -0.25 -30   20 -0.25 -30   20 -0.25 30
0 !TEXMAP END

0 !DATA sticker.png
0 !: iVBORw0KGgoAAAANSUhEUgAAAFAAAAB4CAIAAADqjOKhAAAAAXNSR0IArs4c6QAAAARnQU1BAACx
0 !: jwv8YQUAAAAJcEhZcwAADsMAAA7DAcdvqGQAAAEUSURBVHhe7du9DcIwFABhk5WgQLSsQM0UjMEU
0 !: 1BQsQIsoYAt6NkAYxQV/JQ7WvfuKkFTR6UmOFJzR9bJLkXTlNwyD6QymM5ju5Tl8m67KGUt3XJcz
0 !: J/yY8HZ/6C8BFvNZPoaesMF0BtMZTGcwncF0BtMZTGcwncF0BtMZTGcwnf8t0bmLh85gOoPpDKYz
0 !: mM5gOoPpDKYzmM5gunDBf3tN+/zqNKt367cbOeGUTstxf1nJZHPOx68T/u3XB5/7/zMXLTqD6Qym
0 !: M5jOYDqD6QymM5jOYDqD6QymM5jOYDqD6QymM5jOYLpwwW3t8ajBXTxtTHgwLlp0BtMZTGcwncF0
0 !: BtMZTNfKZzyDiT3hCFy06IIFp3QH/CBMh66aBy4AAAAASUVORK5CYII=

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