I think the sample *.m3g files (and the methods used to load and display them) look neat. I also noticed that Blender has an exporter for *.m3g with support for textures, armatures and animation. Gerhard Völkl clearly put a lot of work in this exporter, topping 3000 lines of code in a single file (a couple dozen classes in there, it’s actually quite readable).

(note: on a PC you can find the source for blender py scripts under Documents and Settings\User\Application Data\Blender Foundation\Blender\.blender\scripts)

The linked page also provides samples files to help us understand how the exporter interprets blender files. There are two things I immediately want to know:

  • How are animations exported? In Blender, bone animations are not directly connected to armatures. Export plugins typically use a kind of naming convention, and this one makes no exception, for example Talk#A1E10#2 is an action, where A1 refers the target armature, E10 means the animation ends at frame 10, and 2 appears to be the node ID (see below).
  • How are node IDs selected? From sample M3G code, it’s fairly obvious that M3G files, for better and for worse, do not contain named entities. Unfortunately the blender M3G exporter uses a naming convention that requires the artist to insert IDs. Maybe this can be improved a little – for example, we could have a java source file with named constants remapping blender object names from arbitrary IDs.

The M3G exporter also allows direct export to java code (in other words, it can generate code which, when run, will produce a scenegraph).

Useful resources