problem-diagnosis（问题诊断）

Problem Diagnosis

Think like a doctor examining symptoms. Something feels wrong. Your job is to identify the specific principle being violated and prescribe the cure. Systematic diagnosis beats random fixes.

Core Mental Model

When animation feels off, ask: What principle is being violated, and how?

"It doesn't look right" isn't actionable. The 12 principles are your diagnostic checklist. Every animation problem is a principle problem—find which one, and the solution becomes clear.

Diagnostic Framework

Symptom: "Floaty" or "Weightless"

Likely Causes:

• Missing slow-in/slow-out (objects should accelerate with gravity)
• Insufficient anticipation before jumps
• No squash on landing impacts
• Timing too uniform (everything same speed)
• Missing secondary weight (hair/clothing not responding to gravity)

Fixes:

1. Add ease-in at motion start
2. Add squash frames at impact points
3. Include settling oscillations after stops
4. Vary timing based on mass

Symptom: "Stiff" or "Robotic"

Likely Causes:

• Missing arcs (linear interpolation instead of curves)
• No overlapping action (all parts move together)
• Twinning (left and right doing identical things)
• No secondary action
• Timing too uniform

Fixes:

1. Add arc curves to all motion paths
2. Offset timing of connected body parts
3. Break symmetry in poses
4. Add breathing and weight shifts
5. Include micro-movements

Symptom: "Unclear" or "Hard to Read"

Likely Causes:

• Poor staging (elements overlap confusingly)
• Weak silhouettes
• Insufficient anticipation (action comes from nowhere)
• Not enough exaggeration
• Competing attention points

Fixes:

1. Simplify background during key action
2. Push poses to clear silhouettes
3. Extend anticipation timing
4. Increase exaggeration 20%
5. Reduce secondary action during primary beats

Symptom: "Boring" or "Lifeless"

Likely Causes:

• No appeal in character posing
• Timing lacks contrast (no fast vs. slow)
• Missing anticipation-payoff structure
• Insufficient exaggeration
• No secondary action or texture

Fixes:

1. Push personality in poses
2. Create timing contrast (faster fasts, slower slows)
3. Add clear anticipation beats
4. Increase exaggeration of key poses
5. Layer in secondary movement

Symptom: "Cartoony" (Unintentionally)

Likely Causes:

• Excessive squash and stretch
• Over-exaggerated timing
• Physics violations too extreme
• Follow-through too elastic

Fixes:

1. Reduce squash/stretch to 10-20% range
2. Add more frames to smooth extremes
3. Ground with realistic settling time
4. Pull back follow-through delay

Symptom: "Too Fast" / "Too Slow"

Likely Causes:

• Frame count mismatch with intention
• Missing ease-in or ease-out
• Key poses not held long enough
• Anticipation/payoff imbalance

Fixes:

1. Adjust frame count (add/remove in-betweens)
2. Check easing curves
3. Hold key poses 2-4 more frames
4. Rebalance anticipation vs. action timing

Diagnostic Process

1. Identify the symptom — Name what's wrong in plain terms
2. Isolate the problem — Is it the whole scene or specific moments?
3. Check principles systematically:

- Timing and spacing? - Squash and stretch? - Anticipation and follow-through? - Arcs? - Staging? - Exaggeration level? - Secondary action?

1. Test hypothesis — Make one change, evaluate
2. Iterate — If unfixed, try next most likely principle

The Golden Rule

One fix at a time. Animation problems often have multiple causes, but changing everything at once makes it impossible to learn what worked. Diagnose, treat one principle, evaluate, repeat.