I recently stumbled upon the word tween but neither in the meaning as a contraction of between nor as little child. It seems to be similar to to tweak.

I found it in the context of programming like in UIButtonTween of the NGUI library or in the GoKit library saying

Lightweight tween library for Unity aimed at making tweening objects dead simple and completely flexible.

Any explanations or links are appreciated.

1 Answer 1


Tweening is also called inbetweening and is the process of producing frames between keyframes, to result in a smooth animation with the illusion of movement (due to the phi phenomenon).

Traditionally, animators would define set positions of characters and other elements at points along the movie, and then add in the appropriate number of frames in between after that. So e.g. Snow White is drawn in one position, then she's drawn in another position she will be in one and a half seconds later. There would be 34 frames between those if drawn "on the ones" but if a slow movement then repeating each frame ("on the twos") would require only 17 to be drawn, and very slow movement would be fine with maybe nine. Just jumping though would mean there was no animation effect. So there's maybe 34 frames, maybe less, that have to be drawn to be shot in-between the two key frames. Doing that is inbetweening or tweening.

These days, a lot of the work can be computerised even in movie-quality animations, and generally the majority of it in simpler computer animations. (E.g. with CSS transitions on web pages, we need only define a starting appearance, ending appearance, and a duration, to have the web browser tween the whole animation, though we have finer control if we want it). The class and library you found are for doing exactly that, in the context of the animation used in computer games.

The etymology should be obvious.


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