# Physics and Action

Design action as cause, contact, mass, and consequence.

## Feasibility pass

Before prompting, simulate the shot mentally:

1. Where is every body/object at frame one?
2. What force starts each movement?
3. What path, distance, duration, and contact are required?
4. What carries inertia or delay?
5. What changes state?
6. What is the final stable arrangement?

If the movement cannot happen physically or editorially in the allotted time, simplify or split it.

## Physical vocabulary

Specify only relevant properties:

- gravity, mass, inertia, friction, weight transfer, balance;
- contact point, pressure, collision, follow-through;
- acceleration/deceleration and motion vector;
- cloth/hair/feather delay and wind coupling;
- liquid viscosity, splash origin, wake, residue;
- particle direction, density, accumulation, heat shimmer;
- hinge resistance, suspension, vehicle roll, creature wing loading;
- prop weight, grip, wrist/shoulder response.

Keep subject physics, camera physics, and environment physics mutually compatible.

## States, transitions, and action density

For difficult action, begin on a strong executable state: already mid-swing, already inverted, already running, already in contact. Put the approach in another shot when it competes with the main event.

Use explicit transitions only when the model/mode and duration can carry them. A sequence of clear states with causal bridges is usually more reliable than a long chain of preparatory actions.

## Impossible shots

Change the input before overprompting:

- bake orientation or damage into a new state asset;
- supply start/end frames;
- add a layout or depth reference;
- use motion reference for choreography;
- split approach, impact, and aftermath;
- grant camera freedom while locking physics anchors;
- design several anchored coverage variations and edit the strongest pieces.

## Scale

Protect scale with three signals:

1. real-world measurement or ratio;
2. visible frame occupation;
3. comparison with a known body/object.

Repeat the proof only where scale may reset after a cut.

## Vehicles and creatures

Define:

- mass and support/contact points;
- propulsion and response delay;
- direction and speed class;
- rider/passenger balance and attachment;
- moving environment and camera relationship;
- state of wings, wheels, suspension, harness, doors, or limbs;
- safe/required clearance from surfaces.

For water contact, specify which exact body/object touches, where the rest remains, and the resulting spray/wake origin.

## Transformations and destruction

Name material progression, origin, direction, conservation of mass, debris behavior, and what remains recognizable. Separate a transformation into causal beats rather than adjective escalation.

## Failure threshold

Track attempts. After repeated variants fail for the same reason, stop wording iteration and change the production design. Common rescues:

- one action instead of three;
- one subject instead of a crowd;
- a tighter corner instead of a whole room;
- a new asset state;
- a different camera angle;
- a cut at the hard transition;
- another model or generation mode.

## Audit failures

Flag floating mass, frictionless feet, teleporting props, duplicated objects, impossible reach/contact, wings or wheels in contradictory states, water reacting to the wrong body, action without causal force, camera motion that erases the physical read, and time windows overloaded with incompatible actions.