Onion skin

Onion skin shows the frames around the one you are drawing as faint ghosts, so you can see where things were and draw the next step in the right place. It is the single most useful tool for smooth animation.

The name comes from the thin, see-through layers of an onion, and from the old animator's trick of drawing on translucent paper stacked on a lightbox.

Turning it on

Tap the onion skin button in the timeline (the stacked-frames icon) to open its panel, then switch on Show ghost frames. You will see the neighboring frames appear as pale ghosts behind your current drawing. Those ghosts are just a guide, they are not part of your frame and will not be exported. The little picture at the top of the panel previews how your current settings will look.

Settings

• Frames before / Frames after: how many previous and upcoming frames to show as ghosts (0–5 each; usually one or two of each is enough). Drag the sliders to set them.
• Before blend / After blend: how faint the earlier and later ghosts are, set independently.
• Loop (wrap around ends): see below.
• Colour the ghosts: off by default. When off, ghosts show the real drawing (or an imported image) faintly. When on, earlier and later frames are tinted different colours (for example red for before, green for after) so you can tell at a glance which way things are moving. The colours are yours to pick.

Loop: what it does (and why the last frame may show the first)

DoodLoop animations loop, so Loop lets the onion skin wrap around the ends of your timeline. With Loop on, the last frame shows the first frames as "after" ghosts, and the first frame shows the last frames as "before" ghosts.

That is intentional: it lets you line up the end of your animation with the beginning for a seamless loop.

If you have 8 frames and see frames 1 and 2 as ghosts while drawing frame 8, that is Loop doing its job. Turn Loop off if you only want the ghosts of the frames right next to the current one.

How to use it

Draw frame 1. Add frame 2. With onion skin on, you can see frame 1 as a ghost, so you know exactly how far to move your character for a natural step. Repeat all the way through, and your motion stays consistent. Turn on Loop near the end to match your last frame back to the first.