Explaination of LXFML file contents

Question

I am interested in writing a game that interprets LXF files into worlds (to create a game such as Lego Universe). After finding out how to extract the LXFML file from the LXF archive, I need to know how to interpret the contained LXFML file. Are there any detailed descriptions of how the LXFML format works?

Answer 1

The LXFML file is an XML document, and there's an XSD document that you can use to validate any LXFML file, along with a textual description of the tags on the LUGNet forums supplied by the LDD Team a few years ago:

LXF files - info and XML schema

The key parts of the LXFML you're going to be interested in start with the <Scene> element, which contains one or more <model> elements, which in turn contains one or more <group> elements, which are made up of <part> elements.

The tricky part is getting from a <part> element to an actual model:

<Part refID="0" name="m3680_turn_plate_2x2__lower_part_0" designID="3680" 
      materialID="1" assemblyID="74340" assemblyRefID="0" 
      angle="0" ax="0" ay="1" az="0" tx="0" ty="0" tz="0" />

As you can see, the Design ID corresponds to a LEGO element [part:3680] so you'll need some way to get from those to a suitable model - I recommend taking a look at either:

• BricksViewer - A Java app for viewing .lxf scene files - also has a brief discussion of the .lxf and .lxfml formats.
• LDXNA - An XNA library for importing LDraw models - it does include an .lxfml document in one of its examples, but I don't recall it using it - however it does show you how to convert the LDraw parts library into a usable format. I've updated this (locally) to work with XNA 4.0, I probably ought to submit a patch to update the project.