Introduction: 2D Moire (Slit) Animation

About: I'm an inventor / maker / designer based in the Bay Area. My background is in residential architecture, film set design, animatronics, media arts, exhibit design, and electronics. I use digital design and fabr…

This instructable will show you how to create a 2D animation using only images printed on acetate and paper. The moire effect is an optical illusion created by parallel lines crossing over each other in the field of view; you can use this effect to make looping animations with the simple Photoshop setup you can download here and a desktop printer. You can find plenty of examples on Youtube.

Materials you'll need:
1. Black mat board
2. Metal straight edge and an ex-acto (or some other cutting tool)
3. Glue (I used generic neutral ph adhesive)
4. Desktop inkjet printer
5. Photo paper (8 1/2" X 11")
6. Acetate or inkjet transparency paper
7. Masking tape

Step 1: Animation Frames

The first step is to make the animation. I made this one from one of Eadweard Muybridge's motion studies.

I chose this series of photographs because each one has the running man centered, they're shot from the same angle, and he's the same size in each one. I made a new layer out of each frame and overlapped them so that I could experiment with which frames would make for the most convincing animation- you can do this by overlapping your frames and turning the layers on and off in sequence. I then cut the background out of each picture so that I could later use the silhouettes. 

I think cutting your animation into 4 frames is about as good as it gets for a looping animation. For a simpler animation you could go with 3 frames, but for the man to look like he's running you need the 4th frame as an intermediate between the 3rd and 1st to make it loop smoothly. I haven't tried it, but I think 5 or more frames would cut out too much of the picture for it to be legible, you'll see why later.

The frames that seemed to give me the most convincing sequence of motion are highlighted in red.

Step 2: Animation Masks

The next step is to make masks for each of the frames. The animation effect is achieved by moving a sheet of acetate with a series of parallel lines that obscure all but one frame at a time, so each of the frames must be cut into lines that are the same width as the space between the opaque lines on the acetate.

After playing around with spacing the lines, I found that the best spacing was 1/8" (.125") between the lines with the lines masking the animation frames being .04". The solid .125" line obscures 3 frames, so each frame is .125" / 3 = .04". This spacing makes for a legible animation frame while being tight enough that each frame reads clearly while the acetate mask is moving.

I made a layer with black lines of these dimensions as a way to quickly get the mask for each of the animation frames: .04" black lines spaced .125" apart. Just CMD+Click the layer and you get the selection you need, then select the frame you want to mask in the Layers Window and click the icon at the bottom of that pane that's a rectangle with a circle in it. This will mask the selected layer using the selection you made. Repeat this step for each of the 4 layers, but of course you'll move the mask to the right by .04" for each layer. 

The end result looks like it's been through a paper shredder, but it gives you isolated frames offset at the proper distance to give you an animation when the acetate is moved over the picture.

Step 3: Silhouettes

The best way to make the animation pop is to get rid of any detail on the animation frames and make them black and white silhouettes. I made this one white on black, but any strong contrasting colors will do the trick.

The easiest way to make a silhouette is to select layer, bring up Hue / Saturation in the menu, and turn the "Lightness" to 100%, giving you solid white. Repeat this step for all your animation frames.

Step 4: Acetate Mask

The acetate mask with the opaque lines will be the opposite of the animation frame lines. Since the animation frames are opaque strips .04" wide with .125" gaps in-between, the acetate mask will be opaque lines .125" wide with .04" gaps in-between. Just print this on an 8 1/2" X 11" sheet of acetate or transparency paper and trim it later.

Step 5: Cardboard Frame

I decided to make a cardboard frame with a window in order to keep the animation print and the acetate aligned properly (also it'll look cooler on my coffee table than a couple of sheets of paper). 

The window in the center is slightly smaller than the animation print so that you won't see the edges of the print. The "SCORE" lines will enable you to make a straight fold in the cardboard as I'll describe later. You can design whatever you want for the frame, this is a generic box to get the job done. 

Step 6: Making the Matboard Frame

Now it's time to start working with your hands!

Print the frame layout on plain paper to use as a template to cut out the matboard. In the attached photoshop file, I've made layer comps for all the prints you'll want to make; this one is called "layout"

Tape the print to your matboard and cut it out with an exact-o. The "SCORE" lines should only be cut about half way through. 

Next, cut out another piece of matboard that's the same size as the front frame. This will be your back board.

Cut out a piece of acetate that's the same with of the frame and longer by about 1/2". You'll glue this onto the inside of the frame to give you a separation between the animation frame and the mask acetate. I added this separation because I wanted to be able to switch out the animations later; there's no need to glue down the picture if it's not touching the mask acetate. This step is tricky, so if you only want one animation, you can skip this step and just glue the animation print to the back board.

Once you've got all your pieces together, glue the back board to the two flaps. The last photo on this step shows the animation print being inserted behind the acetate layer. The mask acetate goes on top of the clear acetate that's glued to the matboard frame.

Step 7: Insert the Mask & Animation

You're almost done. Just cut out the animation sheet and the acetate mask and slide them into the matboard frame. You should end up with an awesome looping animation by simply moving the acetate from side to side. Enjoy!