one movie, two worlds — the side you believe you're on decides which direction you see
One movie, two worlds. This is a real 3D simulation of a dotted torus. The dot layout is mirror-symmetric: every dot at ring angle θ has an identical twin at −θ. Because of that, two genuinely different worlds project the exact same movie onto your screen:
· World A — you are above the torus, and it spins clockwise (seen from above).
· World B — you are below it, and it spins counter-clockwise (seen from above).
Both movies are pixel-identical — verified at startup ✓. So the toggle cannot change a single pixel: it only changes which world you believe you're in. One picture, two truths, and your brain silently picks one — that is the illusion.
The red dot is the one dot you can actually track. It crosses the top of its orbit moving rightward. If that top is the far rim (World A), the spin is clockwise; if it is the near rim (World B), the very same motion means counter-clockwise. Click any dot to move the marker and test its orbit.
Resolving the illusion. The big slider below asks a simple question for every dot: could you see this point if the torus were solid? Slide it away from the middle and the dots that the solid body would hide — the back of the tube, the inner walls facing away — gradually fade away. To the right you are above the torus: the red dot survives only along the lower (near) half of its orbit and vanishes behind the solid body above — the spin is clockwise. To the left you are below it — exactly the opposite, counter-clockwise. The transition is perfectly smooth: near the middle nothing changes at all, and there is never a hard flip.
Towards the ends. Push the slider further out and the central beam — a rod through the hole, along the spin axis — smoothly fades in. It sits exactly on the symmetry axis, so with no solidity it is identical in both worlds; but with the body solid, the rod's lower stretch is hidden when you are above and its upper stretch when you are below. Same rod, opposite occlusion — flip the side and the beam tells you instantly which world you are in. At the very ends, a faint outline of the torus boundary appears as the final resolution cue — including the inner line where the front and back parts of the torus touch visually: the upper arc when you are above, the lower arc when below.
Keys: 1 / 2 slide to the right / left end · E extended mode · space pause · R red dot · T trail · P path · B beam · O outline · click any dot to follow it. Extended-only keys jump straight into the extended panel. Impressum