What is keyframe animation?
Keyframe animation is a method in which the animator sets a value — a position, a rotation, a color, a light's brightness — only at chosen moments called keyframes, and the software calculates every frame in between. Those calculated frames are the in-betweens, and how they are calculated, the interpolation, decides whether the motion reads as mechanical or natural.
The short answer
A keyframe is a value recorded at a point in time on one property. Two keys on the same property define a change, and interpolation fills in the frames between them. Nearly all 3D animation — in Blender, Maya, Cinema 4D, After Effects, game engines and Mixos Studio — is keyframes on per-property tracks, plus curves that control how each value travels from one key to the next.
Where the term comes from
The word predates computers. In hand-drawn animation, lead animators drew the key poses of a scene — the extremes that define an action — and assistants called in-betweeners drew the frames that connect them. The key poses carried the performance; the in-betweens carried it smoothly from one pose to the next.
Computer animation kept the division of labor and handed the in-betweening to the software. That is where the word tweening comes from, and it is why the skill in keyframe animation is still choosing the keys well rather than producing frames.
What a keyframe actually stores
A keyframe is a pair: a time and a value, on one property. A property that has keys is called a track, a channel or an F-curve depending on the application. Position is usually three tracks — X, Y and Z — so a ball can travel steadily on X while its Y is keyed separately to bounce.
Anything numeric can be keyed, not just movement. Light intensity, a camera's focal length, a material's roughness, a shape key's weight and a modifier's parameters are all ordinary tracks. That is how a lamp fades up, a lens pulls focus, or a face blinks, with the same tools used to move an object.
Interpolation: the frames you did not set
Between two keys the software has to invent values, and interpolation is the rule it uses. Linear moves the value at a constant rate. Constant — also called stepped or hold — keeps the value until the next key and then jumps. Bezier, or spline, interpolation passes a smooth curve through the keys, with handles on each key that control how the value accelerates away and slows in.
The choice matters more than beginners expect. The same two keys can produce a robotic slide, a snap, or a move that eases out and settles, depending only on the interpolation — which is why animators spend as much time on curves as on keys.
Rotation needs particular care. Rotations keyed as three angles (Euler) can flip or wobble when the angles wrap past 360° or when two axes line up, a problem called gimbal lock. Quaternion interpolation avoids it, which is why engines and file formats such as glTF store rotations as quaternions.
Keyframes and the other ways to make motion
Motion capture records a performer and produces a key on every frame — dense data rather than a handful of chosen poses. It can be edited like keyframes, but thinning or layering over it is usually easier than retiming every key by hand.
Procedural motion comes from a rule instead of keys: a wave, noise, a spring, or an expression linking one value to another. Simulation computes motion from physics. Both are commonly baked — sampled into keyframes — when the result has to be edited, retimed or exported, because keyframes are what every tool and format understands.
Keyframes in Mixos Studio
Studio's timeline keys position, rotation and scale per axis — Set key records all three at the playhead — and material, light and camera values from the key dot beside them in the inspector. Auto keeps recording as you work: every change becomes a key at the current frame until you turn it off.
Between keys it offers Linear, Hold, Ease in, Ease out and Ease presets, a library of standard easing curves, and bezier handles you drag in Curves mode. Procedural motion sits beside the keys as drivers — a wave, noise, a spring or a bounce added on top of what the keys pose — and a rigid-body simulation can be baked to keyframes, so every source of motion ends up in tracks you can edit.
Frequently asked questions
What is a keyframe?
A keyframe is a value recorded at a specific time on one property — for example, an object's height at frame 12. Animation software interpolates between keyframes to produce the frames in between.
What is the difference between keyframes and in-betweens?
Keyframes are the frames the animator defines; in-betweens are the frames between them. In hand-drawn animation assistants drew the in-betweens; in 3D animation the software calculates them by interpolation.
What is tweening?
Tweening, short for in-betweening, is generating the frames between two keyframes. In 3D and motion-graphics software it is done automatically by interpolation, and the easing curve controls how the value speeds up and slows down along the way.
Is motion capture keyframe animation?
Not in the usual sense. Motion capture records a performance as a key on every frame, rather than a few poses chosen by an animator. The data lives in the same tracks and can be edited with the same tools, but it is dense, so it is usually adjusted or layered over rather than retimed key by key.
What is auto-key?
Auto-key records a keyframe automatically whenever you change an animatable value, at the current frame. It is fast for posing, and easy to leave on by accident — a stray adjustment becomes a key. In Mixos Studio it is the Auto toggle in the timeline header.
Set two keys on anything in a scene and scrub between them — that is the whole idea, in a browser tab.