tweenauksen

Tweening, also known as in-betweening, is the process of generating intermediate frames between two keyframes to create the appearance of motion or transformation in animation. In Finnish, the term is tweenauksen. The technique is used in 2D and 3D animation, computer graphics, and UI transitions.

In practice, tweening involves interpolating values for properties such as position (x, y, z), rotation, scale, opacity, color, or morph targets between the start and end keyframes. It can include motion tweening (transform properties) and shape tweening (morphing between shapes). Some workflows combine manual frame-by-frame keyframes with automated in-betweens.

Common interpolation methods include linear interpolation, easing curves (ease-in, ease-out, ease-in-out), and cubic or spline curves. For rotations, quaternion interpolation or slerp avoids issues like gimbal lock and spinning artifacts. Advanced shape tweening computes vertex-level transitions to morph one shape into another.

Historically, in traditional animation, in-between drawings were created by assistants to smooth out motion. With the rise of digital animation in the late 20th century, software began automatically generating in-betweens; Flash (Macromedia/Adobe) made tweening a central feature for web animation, influencing industry practice. Modern 3D pipelines use keyframes and interpolation to drive rigs and morph targets.

Applications include feature films, television, video games, web content, and user interface motion design. Limitations arise when in-betweens cannot capture complex timing or deformation, leading to unnatural motion or artifacts; artists may adjust tangents, hold frames, or switch to frame-by-frame animation when necessary.