The Carp and the Seagull


The Carp and the Seagull

19th of November, 2012


Recently, for the past 2 months, I've been involved with a company called Nexus Interactive Arts on a webgl project called The Carp and the Seagull. Its an interactive movie directed by Evan Boehm and its rather good.

The story revolves around our chap, Masato. He is a fisherman who is doomed, basically. The story is told in 4 chapters inside a cube. As the cube is spun we see the real world and the netherworld, lighting strikes, fish jump and our fisherman fishes. The story is a classic tale of one man's life going wrong.

The technical challenges on this project were considerable. Initially, I was brought in on the assets. How do you deal with animation from a production studio in a webbrowser? Nexus has a whole fleet of professional animators working in 3dsmax, maya and all the rest. The animation in this movie is excellent, but the problem with animation is the filesize.

Initially, we tried using skeletal animation; exporting the fbx file and attempting to parse it in python, converting to JSON. This proved very tricky and in the end, what we had were glitches.

Shame really, because skeletal animation uses less space and has the ability to be deformed on the fly. In the end we decided to settle with morph targets. The problem with morph targets however, is they are essentially a new set of vertex positions everyframe. Uncompressed JSON for one character using JSON in the three.js format would weigh in at around 8 megabytes! Quite the challenge.


How do you get from 3DSMax to Three.js JSON format though? The answer, it seems, is not easily. We decided to go with the venerable MD2 format. There is an exporter for max that will spit out MD2 files. Writing a python convertor from MD2 to JSON worked a treat. Now we had a way to combine animations from different files, export the various animations and create the lovely assets.


My first solution was to use GZip compression on the fly. In addition, I modified the three.js format to encompass multiple models in one file; a sort of library if you will. This managed to get the filesize and number of requests down considerably at the cost of some processing time.

Another chap, the lovely Roxlu came up with a simple binary format for our files. I wrote a quick JSON to binary python script and meshed it with Roxlu's loader. The compression rate was comparable, if not better than using gzip.

With the assets out of the way, the rest was down to the arts team. I spent most of my time adding extra functionality, fixing bugs and working with the remaining javascript. Three.js is quite a good library. There are a few problems with it; documentation being one of them. I missed the fact that was a handy class for generating vertex normals - would have been handy but it was burried in an example.

One problem we had, and in fact, all Mac Users will have, is to do with Anti-Aliasing. Given that the art in this project uses a lot of lines, the lack of antialiasing was going to be a killer. Only certain cards would do this. Annoyingly, there is no way to test for whether or not this has been enabled. In the end, the plan was simple; render a small 4 x 4 area of the screen with a line and then sample part of it. If you see any grey, you know you have antialiasing enabled. This seemed to work and was quite a nice fix.

FXAA is supported in three.js through the FXComposer - a really nice class that allows many screen based effects to be stacked together. In the end, we decided not to use it as the effect didn't look too great. In addition, there is a fault with certain machines and setting the line width in WebGL - lines can only be drawn with a thickness of 1. This means you dont have anything to blend with.

Three.js is a good library. Some of the good things are the uber-shader, the idea of shared geometry and the FXComposer. Initially I was skeptical with the material paradigm but actually, it works quite well. The maths library is not so intuitive sadly and the animation format is still in its early stages but overall, a nice library to work with.

Working for a client like Nexus is quite tough but enjoyable. As the project progressed a learnt a little more about how a WebGL application might be structured and the weaknesses of javascript. There is quite a bit I'd do differently next time. I think finishing my CoffeeGL library might be a good start.