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Fact File2.12 Tweening and onion-skinning


Tweening is the process of producing intermediate frames "in between" the key frames of an animation to give the impression of continuous movement.

In traditional hand-drawn animation the main artist would produce the key frames and the "in-between" drawings were the responsibility of an assistant. Computer technology now enables designers to specify how a particular character or object should change or evolve without the need for assistants.

The Evian 'We will rock you' animation by soandsau that you viewed in Section 1 is an excellent example of tweening, as the water drops morph continuously into different forms:


Traditional pre-digital animation used light boxes or transparent drawing tables with lit from below to stack drawings above each other. In this way animators could register the placement of elements to ensure that transitions were smooth and consistent.

Computer software employs a labour-saving technique called "onion skinning" to stack semi-transparent frames above each other for the same purpose. Elements can also be placed on separate layers.

Tweening in DrawPlus keyframe animation mode

Keyframe animation offers a powerful and efficient animation technology, as it saves having to draw every frame. Essentially, the technique lets you create key frames through which objects animate. Each keyframe contains key objects that can be assigned a position, rotation and different attributes or actions.

Intermediate steps between key objects are created automatically by the program and produce a smooth professional-looking tweened transition.


The storyboard shows a very simple tween in three steps between the first and last frames: the ball moves from left to right, changing colour and scale. This is achieved by duplicating the first keyframe, selecting the desired number of steps for the transition and affecting changes to the key object in frame 5. Frames 2, 3 and 4 are generated automatically. When the key object is then placed at the bottom of frame 3, frames 2 and 4 adjust automatically.

Tweening in DrawPlus frame-by-frame or stop-frame mode

Although tweening is commonly associated with keyframe or Flash animation, you can also achieve a similar effect when creating animated GIFs in Serif DrawPlus frame-by-frame mode by using the Blend tool. This merges two objects in a user-determined series of steps, as with the dog morphing between the first and last drawings in the illustrations below.


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