# Same poses, same frames. One looks alive. Why?

- Series: [How It's Clipped](https://miu.fm/howitsclipped.md)
- Published: 2026-10-15
- Page: https://miu.fm/howitsclipped/same-poses-same-frames-one-looks-alive-why

## Story

Same poses, same frames. One looks alive. Why?

In computer animation the animator sets key poses and the computer fills in the frames between them. Left to the math, motion looks mechanical; as John Lasseter put it in 1987, "Straight inbetweens can completely kill the essence of an action." Lasseter had learned Disney's principles from Frank Thomas and Ollie Johnston, and at SIGGRAPH 1987 he spelled them out for computer animators with his short Luxo Jr. (1986): squash and stretch that keeps the volume, arcs instead of straight lines, loose parts that arrive late. Smoother math was not the answer. The smooth curve dipped the lamp's heavy base under the floor around each hop, until two extra keys pinned it. Life is in the spacing between the poses: frames bunched near each pose, one fleeting frame through the middle. In 2000, psychologists showed that one plain shape can look alive just from how it changes speed and direction. Lasseter's own words: all this exaggeration was to make the film more realistic.

The balls, the lamp and the graphs here are our own drawings, not images from the film.

Which movie trick should we take apart next?

Sources: John Lasseter, "Principles of Traditional Animation Applied to 3D Computer Animation", Computer Graphics 21(4), SIGGRAPH 1987 (Pixar); Tremoulet and Feldman, "Perception of animacy from the motion of a single object", Perception, 2000.
Sounds: our own, made in code (earshot, CC0).

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