Inbetweens

In animation, inbetweens, also called in-between frames or tweening, are the frames drawn or generated between key poses to create the illusion of continuous motion. They interpolate position, timing, and weight from one keyframe to the next, determining how an action unfolds over time.

In traditional hand-drawn animation, key animators establish the major poses, while assistants or trained technicians called inbetweeners fill in the frames between them. The number of inbetweens between poses shapes the speed of the action and requires careful attention to arcs, easing, and anticipation.

Digital workflows often use onion-skinning tools that let artists see several frames at once, helping them draw in-betweens more accurately. Many software packages also provide automated tweening that interpolates position, rotation, and other properties, though artists frequently refine or replace automated frames for better timing and appeal.

In 3D animation, the computer generates in-between positions along animation curves, with the animator adjusting keyframes and easing curves to control motion. In stop-motion and other traditional media, the inbetweens may be created by photographing additional frames between poses.

Quality inbetweens contribute to fluid motion and coherence of weight, momentum, and anatomy. Poorly crafted inbetweens can produce choppiness or unnatural motion, while well-timed inbetweens support expressive performance without drawing attention to the technique.

Related concepts include keyframes, tweening, onion skinning, and line of action. Inbetweens remain a fundamental aspect of animation across media and eras.