Nothing stops all at once. When a character halts, their hair keeps moving. When a car brakes, passengers lurch forward. Follow through and overlapping action capture how different parts of a system respond to forces at different rates—the principle that makes animation feel physically grounded.
Follow Through: When the main body stops, appendages continue moving due to momentum, then settle. The termination behavior of motion.
Overlapping Action: Different parts move at different rates throughout motion, not just at stops. Hair doesn't start moving when the head starts—it drags behind, then catches up. The continuous offset of timing.
Excessive follow through: Elements feel disconnected, floaty
No hierarchy: All parts moving with same delay
Linear settling: Follow through should ease out, not stop abruptly
所有元素同时停止：会产生机器人般的机械感
跟随动作过度：元素会看起来脱节、轻飘飘
无层级差异：所有部件的延迟都相同
线性沉降：跟随动作应该缓出，而不是突然停止
The Stagger Formula
交错公式
For believable overlapping action, offset secondary elements by 2-4 frames (at 24fps) per level of hierarchy. Root moves on frame 1, primary on frame 2-3, secondary on frame 4-6, tertiary on frame 6-10.
Follow through should never snap to rest. Use ease-out curves with slight overshoot:
Quick initial movement past rest position
Slower return toward rest
Possible micro-overshoot in opposite direction
Final ease to stillness
跟随动作绝对不能直接跳到静止状态。使用带轻微超调的缓出曲线：
初始快速运动超过静止位置
缓慢向静止位置回落
可能会向反方向产生微小超调
最终缓动到完全静止
Implementation Heuristic
实现指引
Identify all elements that could move independently. Assign each a drag value based on mass, flexibility, and distance from root. Apply timing offsets proportional to drag. Add settling oscillation to termination. When motion feels stiff, you probably need more overlapping action.