Image and Illustration Sourcing Guide

Optical illusion sites live or die on their visuals, which creates a real temptation to grab whatever image ranks first in a search result. This page explains why we don't do that, and how images and illustrations are actually sourced here.

The problem with "classic" illusion images

A lot of the images people associate with famous illusions - a particular rendering of the checker shadow illusion, a specific photograph used to demonstrate the Ames room, a particular Magic Eye pattern - are not public domain just because the illusion itself is old or the underlying idea has been described in textbooks for decades. Many were created by a specific researcher, illustrator, or publisher for a specific paper, book, or demonstration, and that person or publisher retains copyright over their particular rendering of it, even if the illusion concept predates their version by a century. Treating "it's all over the internet" as equivalent to "it's free to use" is a common and risky mistake for illusion content specifically, precisely because the genre leans so heavily on a small set of iconic images that get endlessly reposted without their original licensing being checked.

Our approach: build it ourselves

Wherever an illusion's visual structure can be faithfully recreated with code - wireframe geometry, checkerboards, grids, converging lines, color swatches, simple animations - we build it as original CSS, SVG, or small JavaScript rather than sourcing a photo or scan. This has three advantages: there's no licensing question to resolve, the demo can usually be made interactive (a slider, a toggle, a proof) in a way a static photo can't, and we control the exact colors and values involved, which matters for illusions like the checker shadow effect where the whole point depends on precise, verifiable pixel values.

You'll see this on pages like the Necker cube, checker shadow illusion, rotating snakes, spinning dancer, and Shepard tone, all built this way rather than as reused images. The full list is on the Interactive Demos page.

Original illustrations

Some illusions can't be meaningfully rebuilt in code - an Ames room, a piece of anamorphic street art, a camouflaged animal. Those pages use original illustrations made for this site instead, credited as such in the caption. They're there to show what the effect looks like, and the text on each page explains how the real-world version works.

When a photo or real-world reference genuinely can't be recreated

A few illusions are tied to one specific photograph or piece of footage. The dress is a single 2015 photo; the McGurk effect needs synchronised video and sound. For pages like these, rather than reproduce a copyrighted image without a licence, we link to the original where it's legitimately published - Wikipedia for the dress, the BBC's own demonstration for the McGurk effect - and, where possible, build a demo of the underlying mechanism alongside it. If you hold rights to relevant imagery and are interested in a licensing arrangement, or you're the creator of a piece we've described and have questions about how it's covered, get in touch via the Contact page.

Attribution

Where an illustration or demo is inspired by a specific historical figure's original diagram (for example, a wireframe cube in the style Louis Albert Necker used to describe the effect in 1832), the relevant illusion page credits that origin in its "discovered by" details and history section, even though the specific graphic on this site was built independently rather than copied.