Animation
Animation is a dynamic medium in which images or objects are manipulated to appear as moving images. In traditional animation, images are drawn or painted by hand on transparent celluloid sheets to be photographed and exhibited on film. Today most animations are made with computer-generated imagery (CGI). Computer animation can be very detailed 3D animation, while 2D computer animation can be used for stylistic reasons, low bandwidth or faster real-time renderings. Other common animation methods apply a stop motion technique to two and three-dimensional objects like paper cutouts, puppets or clay figures. The stop motion technique where live actors are used as a frame-by-frame subject is known as pixilation.
Design
Design is the creation of a plan or convention for the construction of an object, system or measurable human interaction (as in architectural blueprints, engineering drawings, business processes, circuit diagrams, and sewing patterns). Design has different connotations in different fields (see design disciplines below). In some cases, the direct construction of an object (as in pottery, engineering, management, coding, and graphic design) is also considered to use design thinking.
Animation
Anything can be done live-action if you have unlimited time and unlimited money. But it wouldnt have looked like the book and it wouldnt have kept the same emotion as the wonderful paintings that Chris illustrated. So I dont think it would have been as true to the book if it was done live-action.
Robert Zemeckis, Tom Hanks and Director Robert Zemeckis Discuss "The Polar Express", Rebecca Murrary, About Entertainment,