Tuesday, 29 July 2014

My code - MM3D loader for three.js


I previously made a MD2 loader for three.js. But the MD2 format has several problems, it's very outdated, it gets enormous and takes a while to load if you many animation frames, and it does not have skeleton data, so you can't attach things like weapons to the hands or armor to the chest or hats to the head.

So since I had no idea of the hell I was bringing upon myself, I decided to make a MM3D loader. That is Misfit Model 3D loader for those who never had contact with this infuriating piece of code. The quality of the model editor's code should have alerted me. It uses unsigned integers as pointers (so it does not compile for 64 bits) and has class declarations larger than 1kloc. A true case of bad C++. Problem is, the specification looked quite trivial!

Now I have learned what lies beneath the surface of Misfit Model 3D model format.

First, the way the model is stored is quite strange, there are lots of unused flags. And the resulting data structures are all disconnected. For example, the vertices. Vertices of a 3D model have attributes like texture coordinates, for example. Instead of having a vertex data structure arranged sequentially, each of those having flags to say which data is available for the current vertex, the data is arranged all over the file, and therefore each element of vertex information has to have a vertex index. This makes parsing the files a lot harder. I call my index variables in loops letters starting from "i", like "i j k l ...". You know a data structure is no good when you have to go all way down to "l".

Second, the specs don't tell you you have to add the default bone translation and rotation values to the animation keys to get the right values, I had to find this on my own.

Third, the specs contained not one, but two errors, the second of which cost me a lot of time, because I had no idea where it came from. I even thought it could be a problem with three.js animation system.

To speak of which, three.js's animation system, specially for skeletal animation, is horribly non-documented. I had to look at a lot of source code to figure out how to generate the bone and geometry data.

But now that this is over, I am pretty happy, because it actually works quite well. I pretend to use it instead of the MD2 loader for any upcoming 3D games.

Check out the github repo below, and the live demo here. Models are: Ronaldo by me, the others from opengameart.org.


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