This is the second of four installments in VFXWorld’s The Polar Express production diary. Read Part 1. If you have the QuickTime plug-in, you can view two clips showing the performance capture process by simply clicking on the images.

The Polar Express animation supervisor David Schaub.

In the first installment, I took you through the early days of production, and the events that lead to director Bob Zemeckis’ decision to execute this film using motion capture.

In the next two installments, I will focus on performance capture and the work animators do on top of that, which I am calling “MoCap/Anim.” The last installment, to be posted upon the release of the DVD later this year, will focus on the sequences that were keyframed.

Before getting down to the details, I should try to answer a common question: “Why motion capture? Why not shoot live action?” Here are a few reasons:

1) Achieving the painterly stylization of the Chris Van Allsburg book was the primary objective behind making this film. Remaining within a CG world allowed us to reproduce that look with a great level of control.

2) The director can focus on performances and not be burdened with the normal stresses of a live-action shoot (sets, lights, the weather, etc.). The feedback is instant, which would not be the case if we were to animate traditionally.

3) The actors can focus on acting (or “reacting,” as Tom Hanks describes it). It is like performing “in-the-round” without the worry of hitting a certain mark or acting to a particular camera.

4) The camera work is done after the shoot on a “virtual set,” where the director and DP can spend as much time as they like crafting the perfect camera move. As a result, there are some physics-defying camera moves in this film that could never have been achieved through traditional means.

5) The director no longer needs to settle on a single performance take -- he can mix and match the best moments from multiple takes. This gives him complete control over the performance, in that he can mold the performance to his liking.

There were a myriad of other benefits that Bob appreciated with this process, including:

“What’s great about doing movies in performance capture is that you spend only 20% of your budget and then you know what you’ve got before you spend the 80%. When you make a live-action movie you send the director and a bunch of actors off and they spend 80% of the money and come back and you ask, ‘OK, do we have a movie here or not?’ So this was very controllable and very responsible.”