This illusion nicely demonstrates how motion integration is performed by our visual system. At the start you perceive a global wave motion across to the entire field. When real trajectories of moving dots are shown, you can see that they simply rotate clockwise with a small phase shift to each other. The dots produce so-called local motion cues for the visual system, which automatically integrates them into a complex motion pattern. Note that when trajectories are shown, a percept of the global motion is much weaker, because an extra information increases possible relevance of the local motion.

This demo is made just with few code lines in EventIDE using GDI+ drawing functions.

MotionIntegration-LocalClockToGlobalWaves.eve