Lenticular Interlacer

Combine two or more images into one interlaced, print-ready PNG for lenticular lens sheets or for hand-scored, zigzag-folded paper, and try the flip or morph on screen first. It runs in your browser, so nothing you load leaves your own device.

How to score and fold your print

This makes a zigzag picture: you see one image from the left and a different one from the right, and it changes as you walk past or tilt the page. You need paper of about 120 to 170 gsm (thicker card is hard to fold neatly), a steel ruler, something to score with (a bone folder, a dry ballpoint pen or the back of a butter knife), and a cutting mat or a few sheets of scrap paper underneath.

1. Print at actual size. Choose 100% or Actual size in your print dialog, never Fit to page. Check by measuring one stripe with a ruler: it should match the facet width you chose. Your paper must be at least as wide as the number of facets times the facet width, and as tall as the picture height plus the two margins.
2. Find the fold lines. The short black marks in the top and bottom margins show where every fold goes: a solid mark is a mountain fold and a dotted mark is a valley fold. Lay the ruler across the page so its edge touches a top mark and the matching bottom mark, then check the edge runs straight along the border between two stripes.
3. Score every line. Press firmly along the ruler with your scoring tool, from the top mark to the bottom mark, once only. Score all the lines from the printed side. On heavier paper, score the mountain folds (the solid marks) from the back instead. Try one line on a scrap first so you know how hard to press.
4. Fold alternately. With the picture facing you, fold the solid marks as mountains (the fold points towards you) and the dotted marks as valleys (the fold points away from you). Going from the left they alternate: solid, dotted, solid, dotted, and so on. Image 1 will then show when you look from the left, and image 2 from the right. If they come out the wrong way round, set Strip order to Reversed, or simply swap the two images. The marks update to match, so always follow the marks on your own print.
5. Press it flat like a fan. Collapse the whole sheet into a concertina, run your thumbnail or the bone folder along each fold, then put a heavy book on top for a few minutes. This gives every fold a sharp, even crease.
6. Open it up and stand it. Open the folds until each stripe is at about a right angle to the next. Glue the first and last stripe to a backing board, or slot the two ends into a frame or base, so the zigzag holds its shape. Trim the margins off with a craft knife once it is mounted, or leave them as a border.
7. View it from the side. Stand a little to the left to see image 1, a little to the right to see image 2, and move between to watch it change. Stand a short distance back, because the picture needs room to come together.

Tips: bold, simple pictures with strong contrast work best, and a smaller facet width gives a smoother picture but means more folds to make. Use an even number of facets so the sheet starts and ends on the same kind of fold. An accurate ruler matters more than anything else: a fold that is off by one millimetre shows as a crooked stripe.