Tweening

What is Tweening?

Tweening is how animation creates the smooth frames between two key poses: either drawn by hand in traditional animation or calculated automatically by software, so motion looks fluid rather than jumping from one position to another.

At a glance

Also known as
In-betweeningInterpolationMotion tweeningKeyframe interpolation
Used for
Generating intermediate animation frames between defined keyframes automaticallyCreating smooth, fluid motion between start and end states in digital animationControlling how animated elements accelerate and decelerate through easing curvesUnderstanding how AI video models interpolate visual states in transformation shots
Key features
Computes intermediate frames between keyframes using interpolation algorithmsEasing controls ( linear, ease-in, ease-out, ease-in-out ) shape motion characterEase-in-out produces the most organic, physically believable motion qualityConceptually analogous to how AI models generate intermediate transformation frames

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How it compares

How it compares

Compared with related concepts

Tweening is distinguished from cut or frame-by-frame animation by the principle of interpolation: tweening computes intermediate states automatically from defined endpoints, while frame-by-frame animation defines every single frame independently. Frame-by-frame animation allows complete artistic control over every intermediate position: the animator can create the specific poses, timing irregularities, and physical expressiveness of each frame individually: while tweening trades this control for efficiency, computing the path between keyframes algorithmically. High-quality character animation often combines both approaches: key poses and important breakdown frames are defined manually while less critical intermediate motion is handled by the software's tween, with the animator refining the easing curves to correct mechanical-looking motion.

Think of it like…

Imagine a flip book where only the first and last drawings on each sequence are completed, and all the pages in between are blank. Tweening is the process of filling in those blank pages to create the smooth motion from first to last: in traditional animation, junior artists would draw each page by hand; in digital animation, the software calculates what each intermediate page should look like based on the mathematical path between the two complete drawings. The quality of those in-between pages: whether the motion eases naturally or moves at constant speed: determines whether the resulting animation feels alive and physical or mechanical and rigid.

Pro tip

When applying easing to animation tweens, resist the temptation to use the software's default linear interpolation or uniform ease presets for everything. Examine the physical or emotional quality the animated movement should communicate: a heavy object coming to rest needs strong ease-out deceleration; a character springing into action needs ease-in acceleration; a UI element snapping into position may want a brief ease-out overshoot that settles back, communicating responsiveness through subtle follow-through. Taking the time to adjust easing curves individually for each animated element is one of the highest-leverage quality improvements available in digital animation, transforming mechanical motion into physical presence.

Types and variations

  • Tweening takes several forms depending on the properties being interpolated and the software context.
  • Motion tweening interpolates the position of an element through space, creating movement from one location to another.
  • Shape tweening, found in vector animation tools, interpolates the shape of a vector path between two defined forms, morphing one shape smoothly into another.
  • Colour tweening interpolates colour values over time, transitioning an element's fill or stroke colour between keyframes.
  • Scale and rotation tweening interpolate size and orientation respectively.
  • Most animation software allows all of these to be combined and applied simultaneously to the same element, creating compound animated movement where an object moves, rotates, scales, and changes colour concurrently between keyframes.
  • In 3D animation, the same principles extend to the rigged skeleton of a character, with joint positions and rotations interpolated between keyframe poses to produce character motion.
  • Camera animation in 3D also uses tweening for smooth transitions between defined camera positions.

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Common use cases

  • Tweening is the foundational process behind virtually all digital animation production, from motion graphics and UI animations to feature film character animation and game cutscenes.
  • In motion graphics and broadcast design, tweening animates text, logo reveals, and graphical elements with controlled easing that gives the animation weight and polish.
  • In character animation, tweening handles the motion between keyframe poses that animators establish, with the quality of the easing curves determining how naturally the character appears to move.
  • In UI and app design, micro-animation tweening governs how interface elements appear, disappear, and transition in ways that feel responsive and natural.
  • For AI video generation, understanding tweening informs how to prompt transformation shots, morphing effects, and any generation where smooth motion between defined states is the goal: applying the same conceptual vocabulary of start state, end state, and motion quality that governs conventional animation tweening.

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FAQs

What is tweening in animation?
Tweening, short for in-betweening, is the process of generating the frames between two defined keyframes in an animation to create the illusion of smooth motion. In traditional hand-drawn animation it was a manual process performed by junior animators; in digital animation it is calculated automatically by software using interpolation algorithms. The animator defines the starting and ending states of a movement at keyframes, and the tween fills in all the intermediate positions, rotations, scales, and other properties to create fluid motion between the defined points.
What is the difference between linear tweening and eased tweening?
Linear tweening moves an element at constant speed from start to finish with no acceleration or deceleration, which produces technically correct but often mechanical and unnatural-looking motion. Eased tweening applies acceleration and deceleration to the motion: ease-in starts slowly and builds speed, ease-out starts fast and slows into the ending position, and ease-in-out combines both, creating motion that accelerates from rest and decelerates into the final pose. Eased motion is almost always preferable for organic subjects because it replicates the natural physics of objects with mass, producing animation that reads as physically believable rather than robotic.
What is ease-in-out and why is it so commonly used?
Ease-in-out is a tweening interpolation method that starts the animated motion slowly, accelerates to maximum speed through the middle of the transition, then decelerates naturally into the ending keyframe. This pattern replicates the physics of how physical objects with mass actually move: they overcome inertia slowly, reach peak velocity, and decelerate as they approach their destination. Most animated objects that should feel physically real benefit from ease-in-out, which is why it is the most widely used easing method and often the default in professional animation software. It produces the organic, weighted quality that distinguishes professional animation from mechanical motion.
How is tweening used in digital animation software?
In digital animation software, tweening is applied by setting keyframes at the points where you want to define the state of an element: its position, rotation, scale, opacity, or other properties: and the software automatically calculates all the intermediate frames. In most tools, easing is controlled through bezier handles on the animation curve or through named presets like ease-in, ease-out, or ease-in-out. More advanced control is available through the graph editor, where the animator can manually shape the velocity curve of any property over time with precise bezier control points, producing custom motion qualities that standard presets cannot achieve.
How does tweening relate to AI video generation?
In AI video generation, the concept of tweening is relevant when understanding how models generate smooth transitions between defined visual states: transformation shots, morphing effects, and any generation where the clip moves from one state to another. When you prompt a transformation from one scene to another, or a visual style shift within a single clip, the model is performing an automated form of visual tweening: generating intermediate states that plausibly bridge the start and end conditions. Describing the desired quality of this transition ( smooth and gradual, easing naturally, no abrupt changes ) provides expressive guidance about how the intermediate frames should read, in the same way easing curves shape conventional animation tweens.
What is shape tweening?
Shape tweening is a tweening type specific to vector animation tools ( most commonly Adobe Animate ) that interpolates the shape of a vector path between two defined forms, morphing one shape into another over time. Rather than moving an element through space, shape tweening changes its outline: a circle can be tweened into a rectangle, a letter morphed into another letter, or a complex organic shape transformed into a geometric form. The software calculates the intermediate shapes by interpolating the positions of the path's control points between the starting and ending forms. Shape tweening is distinct from motion tweening, which moves an element through space, though both can be applied to the same element simultaneously.
What is the relationship between tweening and the twelve principles of animation?
Tweening directly implements several of the twelve principles of animation developed at Disney, particularly slow-in and slow-out, follow-through, and anticipation. Slow-in and slow-out: the principle that natural motion involves easing at the beginning and end of a movement: is what ease-in-out tweening computes automatically. Follow-through, where parts of an animated character or object continue moving after the main action has stopped, can be achieved through carefully timed tweens that allow secondary elements to lag behind the primary motion. Anticipation, where a character winds up before an action, is set as a keyframe that the tween then moves smoothly through. Understanding these principles provides the expressive reasoning behind tweening choices.
Do I need to understand tweening to use AI video generation tools?
Directly, no: tweening is a technical concept from traditional and digital animation that operates beneath the surface of most AI video generation interfaces. However, understanding tweening is useful context for working with transformation shots and morphing effects in AI generation, where the model is effectively performing automated visual interpolation between defined states. Applying the vocabulary of smooth, gradual, easing motion quality to prompts for these types of shots translates the expressive concerns of good tweening: natural acceleration and deceleration rather than mechanical constant speed: into prompt language that guides the model toward more organic, physically convincing transitions.
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