For this shot I (Eric) did two color keys. The first was to try to establish the basic color and lighting of the shot. Plus, it made the actual painting of the background go much, much faster.
The second was after I finished the background and realized that I needed to help Ben and Stephen figure out the lighting for Wan-chan in this new environment. Lighting for 3D rendering is an art of its own and color keys can help Ben and Stephen out with the problems that they inevitably encounter in this process.
After figuring out some of the difficult lighting issues, the animation goes into After Effects for the secondary animation. In this particular scene that means moving the clouds and generally making the environment seem more alive. It's usually around this time that Ben will give me a short clip of his animation which I use as a reference for more painting, in this case, Wan-chan's jet stream.
Having Wan-chan's exact path in front of me means I can take it right into Photoshop and mark out specific points on a path that Wan-chan's jetstream will be following and then paint right on top of them.
I used different colored dots on different layers so I could keep the smoke from his front and back paws separate, since they start at different times.I also included some rougher lines which are meant to show where the shadows are supposed to go. After all of this I give these back to Ben so he can composite them on top of his animation in After Effects. Usually it's here that I'll figure out that my painting is off or something and then I'll take it back and make the adjustments. The result, minus sound effects, is this:
Robo-san and Wan-chan Shot_06.3 from Ben Dallman on Vimeo.