Just like live-action films, animated features are two-dimensional; they are portrayed on a flat screen. And with the exception of the occasional 3-D movie, that's the way it's always been.
Still, it was important to Walt to try to get a greater sense of depth into his films -- and to do so to a far greater extent than was possible through the use of shadows and other artistic devices that create the feeling of three dimensions. As was often the case in his life, Walt turned to technology to accomplish this.
The solution? The so-called multiplane camera. This gigantic device utilized multiple layers of glass -- containing backgrounds, foregrounds, and everything in between -- in conjunction with the camera itself in order to create the illusion of depth.
The multiplane camera was first used in a Silly Symphony called The Old Mill, which was released on November 5, 1937. This served as a testing ground for the use of this tool in Snow White, where it produced some memorable scenes. (Pinocchio was the first feature-length animated production in which the multiplane camera would be used to the fullest.)
Walt was wildly enthusiastic about this innovation. When visitors came to the studio, the multiplane camera was always one of the important stops on his personal tour. The creators of the multiplane camera were recognized for this achievement far beyond the studio walls. On March 10, 1938, they received a special Academy Award® in a scientific and technical category for their creation. (That same day, The Old Mill won an Oscar® for best cartoon short subject.)