I got to spend a very brief amount of time on this show helping the crowd head, Allen Stetson, do some cycle animation tests. We were timing how long it took to keyframe a typical cycle animation. Then we compared this to having to clean up mo-cap, and adding in face/hand animation on top of that. It was only a few weeks of work, but it let me peek into the world they were making of Shadows.
It was....awesome. I saw as much as one initial sequence that went through all the way to lighting and paint fix. I think it would have been an amazing combination of 2D and 3D - and would have developed a fan base amongst those who love Roger Rabbit, etc. Sadly, as was too often the case at DreamWorks, they couldn't nail down the story. And an higher price tag for all the cool hybrid tech became the nail in the coffin for Shadows. There's rumors of Edgar Wright coming in to revist this...so hopefully it'll see the light of day eventually.
Oh, and here's some leaked GIFs that have been floating around online for a few years to give you an idea of the film. The shadows were all 2D hand drawn animation, then were cleaned up on the computer and projected into the 3D scene. It wasn't just as simple as that of course, and I remember seeing a great and complicated demo explaining the processes they developed.
