Moiré illusions can be visually captivating, particularly when a little rotational motion is thrown in the mix. [Dushyant Ahuja] was a fan of these moving Moiré sculptures he’d seen around the place, and decided to create his own.
The build is based around spinning two spoked discs in opposite directions, such that the spokes create moving Moiré patterns as they turn. To achieve this, the discs were 3D printed, along with a central housing containing two 12 volt gear motors. 3D printed gears are used to allow both discs to rotate about the same axis. Nominally, the motors spin relatively slowly, generating a pleasing, hypnotic effect when turning the discs.
The drivetrain is under the control of an ESP8266, though [Dushyant] notes that to get the basic effect, one need only connect the motors to a 12 volt power supply and let them run. However, future plans involve adding some LEDs for bling, and varying the motor speed to create yet more complex effects. With the microcontroller already installed, upgrades should be a cinch.
[Tom Scott] ran across an interesting visual effect created with Moiré patterns and used for guiding ships but we’re sure it can be adapted for hacks somewhere. Without the aid of any motors or LED animation, the image changes as the user views it from different angles. When viewed straight on, the user sees vertical lines, but from the left they see a right-pointing arrow and from the right, they see a left-pointing arrow. It’s used with shipping to guide ships. For example, one use would be to guide them to the center point of a bridge. When the pilots see straight, vertical lines then they know where to steer the ship.
US patent 4,629,325, Leading mark indicator, explains how it works and how to make one. Two screens are separated from each other. The one in front is vertical but the one behind is split in two and angled. It’s this angle which creates the slants of the arrows when viewed from the left or right. We had to convince ourselves that we understood it correctly and a quick test with two combs showed that we did. See below for the test in action as well as for [Tom’s] video of the real-world shipping one.
Moiré patterns are a thing of art, physics, and now tool design! [Julldozer] from Mojoptix creatively uses a moiré pattern to achieve a 0.05 mm precision goal for his custom designed 3D printed calipers. His calipers are designed to validate a 3D print against the original 3D model. When choosing which calipers are best for a job, he points out two critical features to measure them up against, accuracy and precision which he explains the definition of in his informative video. The accuracy and precision values he sets as constraints for his own design are 0.5 mm and 0.05 mm respectively.
By experimenting with different parameters of a moiré pattern: the scale of one pattern in relation to the other, the distance of the black lines on both images, and the thickness of black and white lines. [Julldozer] discovers that the latter is the best way to amplify and translate a small linear movement to a standout visual for measurement. Using a Python script which he makes available, he generates images for the moiré pattern by increasing line thickness ratios 50:50 to 95:5, black to white creating triangular moiré fringes that point to 1/100th of a millimeter. The centimeter and millimeter measurements are indicated by a traditional ruler layout.