Motion blur
The directional smear a moving thing leaves within one frame. Without it, fast motion reads as a stack of crisp stutters.
See it
What it is
A camera frame is not an instant, it's an exposure. Anything that moves during that slice of time smears across the sensor, and your eye reads that smear as speed. The film convention is the 180-degree shutter rule: shutter speed equals one over double the frame rate (1/48s at 24fps), which is why movies look like movies and a 1/2000s action shot looks strobed and hyper-real.
Computers get none of this for free. A CG render or a motion graphic samples one frozen instant per frame, so fast moves arrive as a stack of sharp stills that judder. Turn motion blur on (shutter angle in After Effects, sample count in Blender, per-object velocity blur in 3D) any time something crosses more than a few pixels per frame. It is the single cheapest fix for animation that feels stiff.
Gotcha: it fights readability. Blur a logo or a word as it flies in and the audience gets nothing to read, so ease into a full stop and let the blur resolve. It also costs render time, sometimes a lot. And in a composite the blur has to match: a razor-sharp CG element inside handheld footage that smears on every whip will always separate from the plate.
Ask AI for it
Add motion blur to this animation: enable per-object motion blur with a 180-degree shutter (0.5 frame exposure) and enough samples that fast moves stay smooth rather than banded. Blur should scale with velocity, peak mid-move, and resolve to fully sharp on the final resting frame so text and logos stay readable. Match the blur amount to any live footage in the shot rather than leaving CG elements crisp.