Besides for entertainment, 3D animation and -images are great for explaining complicated structures or processes. They are also excellent for visualising what things will look like before they are actually built. That’s extremely helpful in cases where it is difficult or costly to change the design of your handiwork afterwards: think about architects, wood-workers and the like. It is also a lot more affordable than model-making or presentation prototypes.
The first thumbnail links to some cabinet-making pre-visualisations; the second one to a project to create a realistically rigged complicated mechanical model; and the last one to a satirical 3D animation.