Keyframes, curves and the retime graph

The mechanism

A keyframe records the value of a parameter at a point in time. Two keyframes with different values, and the software interpolates between them, computing a value for every frame in between.

That is all animation is inside an editor: position, scale, rotation, opacity, crop, and any effect parameter, each with a value at a moment in time.

Motion, Sound and Music covers the principles of movement — easing, weight, anticipation. This lesson is the mechanics inside a timeline and the places they go wrong.

Where they live

In Resolve's Edit page, every clip has an Inspector with a diamond next to each parameter. Click it to set a keyframe at the playhead. The keyframes appear in a strip under the clip once you expand it.

The important thing to know: Resolve has two separate keyframe systems. Transform, crop and composite keyframes live on the Edit page's Inspector. Colour page keyframes live in the colour page's own keyframe panel, and they are separate — a keyframe on the Edit page will not appear in the colour page's timeline. This confuses everybody once.

Kdenlive puts keyframes in the effects panel with an inline curve editor. Shotcut has keyframe buttons in each filter's panel. Premiere uses the Effect Controls panel.

Linear is the tell

The default interpolation is linear: constant rate of change from the first keyframe to the second.

Nothing physical moves that way. Objects accelerate and decelerate. So a linear move reads as mechanical, and it is the single most reliable sign that a piece was animated by somebody who has not thought about it.

The fix is easing. In Resolve, right-click a keyframe and choose Ease In, Ease Out or Ease In and Out. The keyframe changes shape and the motion gains acceleration.

As a default: ease out of the start and into the end. Fast in the middle, slow at both ends.

The curve editor

For more control, the curve editor shows the interpolation as a graph — time on the horizontal axis, value on the vertical — with bezier handles on each keyframe.

What the shape means:

• A straight line is linear.
• A curve that starts flat and steepens is an ease out of the beginning: slow start, fast finish.
• A curve that steepens then flattens is an ease into the end: fast start, gentle arrival.
• An S is both, which is the natural-looking default.
• A curve that goes past the final value and comes back is an overshoot, which reads as bounce or springiness.

Dragging the handles is more precise than choosing a preset, and it is worth ten minutes to learn because every animation tool everywhere uses the same graph.

The three animations worth mastering

A slow push. Scale from 100% to 105% across a shot's duration, linear or very gently eased. Gives life to a static shot. This is the one you will use most.

A text entrance. Opacity 0 to 100 over 8–12 frames, with a small position move of 10–20 px, eased out. Subtle, professional, and the entire lower-third animation most pieces need.

A masked reveal. Animate a crop or a mask edge across the text so it appears to be wiped on. Free in any editor, and it looks considerably more made than a fade.

The retime curve

Speed changes have their own keyframe graph, and it works differently enough to trip people.

Resolve's Retime Curve offers two views of the same information:

• Retime Frame — a graph of which source frame plays at which timeline moment. A steeper line means faster playback. This is the one where a speed ramp is a curve rather than a corner.
• Retime Speed — a graph of the speed value itself, as a series of steps.

The practical consequence: a speed ramp made with the Speed view alone produces a sudden change at each step, which is visible as a jolt. To ramp smoothly, switch to the Frame view and ease the keyframes, so the rate of change itself changes gradually.

Two traps

Keyframes belong to the clip, not the timeline. Trim the clip and the keyframes move with it, which is usually what you want and occasionally is not — if you trimmed the head, your carefully timed animation now starts at a different point in the shot.

Scaling past 100% costs resolution. A push from 100% to 130% on a 1080p clip in a 1080p timeline is upscaling for most of its duration. On a 4K source at 1080p it is free, which is another reason to shoot larger than you deliver.

Today

Animate a scale from 100% to 110% with linear keyframes, watch it, then ease both ends and watch it again. The difference is the whole lesson.