From Lawrence D'Oliveiro
The four-dimensional numbers called quaternions do have one not-so-esoteric application (9 November, p 30). The next time you admire some spectacular new piece of computer-generated 3D animation in a film, on TV or in advertising, you could be witnessing the results of quaternions in action. They are used in computer graphics to express rigid-body transformations (translations and rotations) of objects, avoiding the loss of quality that the less clever alternative of re-rendering them for each transformation entails.
Hamilton, New Zealand
