How to 3D print a spiral portrait from a photo

A spiral portrait is one line that winds from the middle to the edge, thick where the photo is dark and thin where it is light. You print it flat, in two colours, with one filament swap. Up close it is a spiral; from across the room it is a face.

Step by step

1. Open the spiral portrait maker and choose a photo: a face, close up, with the light from one side.
2. Choose the shape (square, wide, tall or round) and the width.
3. Crop it so the face fills most of the spiral, and raise the contrast if the face looks flat.
4. Set the number of turns and the line weight, and look at the preview from a distance.
5. Choose Filament swap (any printer) or Multi-colour (two parts, for an AMS or MMU), and the back: flat, a keyhole for a screw, or magnets.
6. Download the 3MF or STL, add the swap in your slicer, and print it flat.

Print settings

• 0.2 mm layers, flat on the bed. Nothing needs supports.
• A 0.4 mm nozzle. The thinnest line is 0.45 mm, just over one line of a 0.4 mm nozzle; with a 0.6 mm nozzle, set the thinnest line to 0.6 mm or more, or the lightest parts drop out.
• 2 walls and 15% infill are fine: the picture is in the outline of the line, not in the infill.
• Turn on Detect thin walls (PrusaSlicer, OrcaSlicer, Bambu Studio) or Print Thin Walls (Cura), so the thinnest bits of line are printed and not left out.

The swap goes in at the layer in the plan. How to add it in your slicer: How to change filament at a layer without an AMS.

Getting a recognisable face

• More turns give more detail, but thinner lines. Around 40 turns for 150 mm is a good start; for a bigger print, add turns.
• Line weight: heavier lines make the whole picture darker. If the face is too dark and loses its shape, go one step lighter.
• Thinnest line 0 lets the line stop in the lightest parts, such as a white background. That gives a cleaner outline around the face.
• Colours: a light base with a dark line looks like a pencil drawing; a dark base with a light line looks like an engraving. Try both with the swap button.
• Look at it from two or three metres away. That is where the spiral turns into a face, on screen and on the wall.

Halftone works the same way

The halftone maker uses dots instead of a spiral, like a photo in an old newspaper. It prints with the same single swap (a 2 mm base and 0.8 mm dots, so also at 2.20 mm, layer 11), or as a plate with holes in one dark filament that lights up in a window.