What is a tween?
Tween is short for in-between: the transition frames between two key poses. In hand-drawn animation a person draws them; in digital tools software usually calculates them. Both have their place, and knowing which to use when is most of the craft.
What automatic tweening does
The software takes the difference between a start and an end pose and generates the frames between them mathematically. For position, rotation and scale the result is flawless: drawing frames by hand to slide an object across the screen is wasted time. In Kipirti the tween generator creates real frames, so you can go back and fix any of them by hand afterwards.
Where it falls short
Automatic tweening cannot change the shape itself. A bending arm, a changing expression, any squash and stretch — those need drawing. Generated transitions also carry motion along a straight line, while living movement travels on an arc. Good tools therefore let you add a curve to the path.
Easing is the character of the movement
Distributing in-betweens evenly makes a move look mechanical. Crowding frames at the beginning and end and thinning them in the middle gives an object weight. Curves like bounce and overshoot pass the target and return, which reads as alive. The same two poses become an entirely different shot with a different easing curve.
Frequently asked questions
Is using automatic tweens cheating?
No. Classic studios split the work too: a lead animator drew the keys and an in-betweener drew the rest. Automatic tweening is the digital version of that division of labour. What matters is whether the result reads as alive; how it was produced isn't the viewer's concern.
How many in-betweens should I use?
It depends on speed. Two in-betweens can be too many for a quick gesture, while a slow drift may need six or eight. The rule: if the motion looks choppy add frames, if it looks like it's dragging remove them.
Can generated in-betweens be edited afterwards?
It depends on the tool. Some programs compute tweens only during playback and you can't touch them. Tools that generate real frames let you open each one and correct it like any other drawing, which is by far the more flexible arrangement.
The brush draws alive. Kipirti is a sketchbook for animation: draw frame by frame, compare with onion skin, and export a GIF or a video. It opens in the browser — nothing to install.
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