Natural motion follows arcs rather than straight lines, giving animation flow and biological authenticity

Almost all living creature movements follow curved, arc-like paths rather than straight lines, because they are driven by rotating joints rather than linear actuators. A thrown object follows a parabola; a hand waving follows a partial circle; a walking figure’s extremities trace looping arcs. When animated motion follows straight point-to-point paths instead, it reads as mechanical or robotic even if the timing is otherwise correct. In generative motion, the principle translates to using sine/cosine oscillation rather than linear interpolation for natural organic movement, applying rotation rather than translation for swinging limbs, and using Perlin noise (which has smooth, curved output) rather than random() for organic variation.

Examples

Replace x += speed (linear) with x = centerX + cos(angle) * radius; angle += 0.05 (arc) — the circular path immediately reads as more natural. Pendulum swings, camera bobbing, leaf flutter all naturally trace arcs.

Assessment

Explain why a ball that moves in a straight line from one point to another looks ‘wrong’ even with good easing, and how changing its path to an arc fixes it. Then write a two-line p5.js snippet that moves a point along a circular arc.