Abstract

Animation turns drawings into movement by placing images in sequence. A major animator draws key-frames, which are the starting and ending poses of an action. Between those key-frames come in-betweens, the drawings or frames that fill the gap and create smooth motion. The process of drawing or generating these in-betweens is known as inbetweening. (Wikipedia) Each in-between matters because spacing (how far things move between frames) and timing (how long each frame lasts) affect how the action feels—fast, slow, heavy or light. This article explains what happens between two key-poses: how breakdowns are used, how spacing and timing are planned, and how digital tools help or change the process. For high-school students considering animation programs, understanding this frame-by-frame phase shows what you will practise in class and helps you build skills early.

Keywords: key-frame, in-between, inbetweening, timing, spacing

In animation you start with major drawings called key-frames. These define the important poses—such as the beginning of a jump and the landing. (StudioBinder) Between those key-frames you insert in-betweens: the drawings that go between the key-poses. The process of creating those is called inbetweening. (morphic.com) What happens between two key-frames is critical: how many frames you use, how far the drawing changes each time (spacing), and how long each frame holds (timing) all affect the feel of the action.

Planning the sequence

Once you have two key-frames, you need to decide how many frames you will use between them. If you use few in-betweens, movement will look fast or snappy. If you use many, motion appears slower or smoother. The spacing between each drawing controls speed: larger shifts between drawings mean faster motion; smaller shifts mean slower motion. Some resources say that in digital animation you often use software to interpolate between key-frames (generate in-betweens automatically) but the animator still controls spacing and timing. (Adobe)

Breakdown poses and arcs

Between two key-frames you often use breakdowns. A breakdown is an intermediate frame that defines how the motion will travel, for example a turning point in movement or a shift in direction. (library.fiveable.me) Arcs are the curved paths objects follow; animators trace motion along arcs so that in-between drawings follow that curve rather than a straight line. That makes movement feel more natural.

Spacing and timing in practice

Suppose a character raises an arm. Key-frame 1: down. Key-frame 2: arm fully up. How many frames between? If you choose five frames, each in-between drawing will show large movement per frame (wide spacing) so the motion looks fast. If you choose twelve frames, each in-between drawing shows smaller movement (narrow spacing) so the motion appears slower and more controlled. Also timing matters: If you hold the final pose for extra frames, the viewer gets time to register it; if you move quickly though few frames, it feels snappier.

In digital tools you might set key-frames and have the software interpolate the in-b-etweens, but the animator still sets key-frames, chooses timing (how many frames), and adjusts spacing by tweaking the interpolation curves. (Pixune)

Digital vs traditional in-betweening

Traditionally, animators drew every in-between drawing on paper or cels. That was labor intensive. (Wikipedia) With digital workflows, software can generate in-betweens automatically, but the animator still must check spacing, timing, and style. (StudioBinder)

What this means for animation students

If you are exploring a university animation program you will be asked to plan sequences, draw key-frames, and fill in the in-betweens or supervise software generated motion. Understanding in-betweening helps you follow instructions such as “create twelve frames between pose A and pose B” or “adjust spacing so the motion accelerates then decelerates”. In assignments you may create exposure sheets listing frame numbers, or timing charts showing how many frames each pose holds. Recognising the terms key-frame, breakdown, in-between, timing and spacing will help you engage with coursework and workshops.

You can practise now: pick a simple action like a character waving or a ball bouncing. Draw the key-frames. Then draw several in-betweens or use software and watch how spacing changes the feel of motion. Try varying the number of in-betweens and observe how the same action becomes fast or slow. Note whether the motion follows an arc or shifts direction, and adjust accordingly.

By working frame by frame you build foundational animation skills. Every in-between drawing matters because sequence and timing produce readable, believable motion.