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Home icon grey.png   ▶ Development ▶ Add-on development ▶ Skinning ▶ Tweeners

A Tween defines how an animation progresses from its initial value to its final value. The simplest way this can be accomplished is to go straight from start to finish in equal steps. This results in a smooth transition, however it starts and stops abruptly and tends to be a bit unnatural. Unnatural in the sense that, in the real world, you never see a linear transition. In the real world, transitions (movements, deformations, etc) are always accompanied by varying degrees of acceleration and deceleration. Some real world examples that come to mind: the movement of a pendulum, a ball bouncing, our breathing pattern, a bungee jump. Tweens basically try to mathematically recreate some of these transitions and can help add naturalism to animations.

What is Easing?

All tweens (except Linear) support an easing attribute that can be one of "in", "out", or "inout". The Quadratic tweener only supports "in" and "out". The default easing method is "out". Easing is basically the direction of the tween action. Looking at the various graphs below and trying the tweens out will make the concept of easing, easier (hehe, say that ten times in a row) to understand.

Supported Tweens

Currently, Kodi's skin engine supports eight different tweens: "linear", "quadratic", "bounce", "elastic", "cubic", "circle", "sine" and "back". They are set in an animation using the tween attribute. The animations next to each graph shows how that tween renders straight motion between 2 points. Tweens however aren't restricted to only motion effects, they can be used on alpha as well.

Linear Tweener

Linear Tweener
Linear Animation

Quadratic Tweener

Quadratic Tweener Easing Out
Quadratic Easing Out Animation

Quadratic Tweener Easing In
Quadratic Easing In Animation

Bounce Tweener

Bounce Tweener Easing Out
Bounce Easing Out Animation

Bounce Tweener Easing InOut
Bounce Easing InOut Animation

Bounce Tweener Easing In
Bounce Easing In Animation

Back Tweener

Back Tweener Easing Out
Back Easing Out Animation

Back Tweener Easing InOut
Back Easing InOut Animation

Back Tweener Easing In
Back Easing In Animation

Cubic Tweener

Cubic Tweener Easing Out
Cubic Easing Out Animation

Cubic Tweener Easing InOut
Cubic Easing InOut Animation

Cubic Tweener Easing In
Cubic Easing In Animation

Circle Tweener

Circle Tweener Easing Out
Circle Easing Out Animation

Circle Tweener Easing InOut
Circle Easing InOut Animation

Circle Tweener Easing In
Circle Easing In Animation

Sine Tweener

Sine Tweener Easing Out
Sine Easing Out Animation

Sine Tweener Easing InOut
Sine Easing InOut Animation

Sine Tweener Easing In
Sine Easing In Animation

Elastic Tweener

Elastic Tweener Easing Out
Elastic Easing Out Animation (animation needs fixing)

Elastic Tweener Easing InOut
Elastic Easing InOut Animation

Elastic Tweener Easing In
Elastic Easing In Animation

See also