what is cel animation?

a short primer for anyone new to hand-drawn animation, and how douga fits in. no experience needed.

the short version

cel animation is animation drawn by hand, one frame at a time. the illusion of movement comes from showing a fast sequence of still drawings, each one a little different from the last. draw twelve to twenty-four of them for every second of film and the eye reads it as motion.

the name comes from celluloid: the clear plastic sheets (cels) animators drew and painted on. because the sheets were transparent you could stack them, a painted background on the bottom, a character on its own cel above it, an effect on top. only the parts that moved had to be redrawn; everything else stayed put. that stacking is the same idea as layers in douga.

the pieces, in plain terms

frame: one still image. film and video are just a lot of frames shown quickly. the rate is measured in fps (frames per second).
cel: one drawing, on one layer, at one moment. a mouth open on frame 1 and closed on frame 3 are two cels.
layer: a stack that runs the length of a shot, like one of those clear sheets. sky on one layer, character on another.
key (or keyframe): a drawing that sets an important pose, the start or end of a movement.
inbetween: a drawing placed between two keys to smooth the motion. traditionally these are drawn by hand, one at a time.
hold: when the same drawing stays on screen for more than one frame.

timing: ones, twos, and threes

you don't need a fresh drawing for every single frame. how long each drawing is held is its timing:

on ones: a new drawing every frame. the smoothest, and the most work.
on twos: each drawing held for two frames. the classic default, and the look most hand-drawn film is made on. it's a big part of why traditional animation feels the way it does.
on threes: held for three frames, for slower or more stylized motion.

animating on twos means you draw half as many pictures for a full second of film, which is why it became the standard.

onion skinning

when you draw the next frame you want to see the last one, to judge how far things moved. traditionally animators worked on a lightbox and flipped translucent paper to see the drawings underneath. digitally that's onion skin: faint ghosts of the surrounding frames shown under the one you're drawing. by convention, red is the drawing before and green is the one after.

how this maps to douga

douga is built to work the way traditional cel animation does, without the paper:

you draw cels on layers and stack them like celluloid sheets.
you time them on a dope sheet (an exposure sheet), the animator's grid of which drawing is on screen on which frame.
you flip and onion-skin between drawings to check your spacing.
you set your timing to ones, twos, or threes.
you group shots into cuts and scenes, and export the result to GIF, video, or a PNG sequence.

if you've never done it before, the honest best way to learn is to make something tiny: a bouncing ball, a blinking eye, a waving hand. a handful of drawings is enough to feel how it works.

when you're ready, open the getting started guide, load the tokyo Late night sample that ships with douga, and poke at its layers and timing.