Halftone relief

A print that responds to light. The monogram is modelled as a shallow relief and printed as a halftone screen, where every cell of the grid is one mark and the darker the surface at that point, the bigger the mark.

Move the lamp and the bevels catch, the shadows swing round the letters, and the screen reprints in real time. Switch from dots to slashes and the same image comes out in lines at 16°, the angle of the slash in off/form.

Halftone is print's oldest trick for faking tone with a single ink. We liked the idea of taking that constraint (one colour, one grid, no greys) and making it answer to something live.

It doubles as a test for the identity. The mark still has to hold when all you have is dots.

1. 1

   The mark is rasterised at one pixel per halftone cell, so antialiasing gives each cell its coverage. Two box blurs round that coverage into a pillowed height field, and surface normals come from its gradient.

2. 2

   Each frame, every cell is lit by a point light: Lambert shading times a distance falloff, multiplied by a cast shadow from a short ray march across the height field toward the lamp. Rays are clipped to the mark's bounding box first, so most of them never march at all.

3. 3

   Brightness sets mark size. A dot's area, or a slash's stroke width, grows with darkness. The screen is drawn as one batched path per frame and capped at 132 columns, so the cost stays flat on big displays.

4. 4

   Left alone, the lamp drifts on a slow Lissajous curve so the shadows keep turning. Under reduced motion it stays exactly where you put it.