---
name: "stop_motion_basics"
description: "Plan, shoot, and finish a stop-motion short: frame-rate math, onion-skinning, lighting lockdown, and rig removal. Triggers on stop motion, claymation, brickfilm, puppet animation, or assembling frame sequences into video."
metadata: { "includeInPrompt": true }
---

# Stop Motion Basics

## Purpose
Get an agent from a blank set to a finished stop-motion clip: choose a frame rate, do the frame math, lock lighting so frames do not flicker, use onion-skinning to move puppets in small increments, and remove support rigs in post. Scope is one scene at a time. No character rigging, no CG, no distribution strategy.

## Workflow
1. **Frame-rate math first.** Pick fps (12 or 15 for a first project, 24 for finished work), then compute unique frames needed: `seconds * fps`. Decide ones vs twos (twos halve the posing work). See `references/frame_rate.md`. Run `bin/frame_calc.py` to get the numbers.
2. **Lock the set.** Tripod or locked-down stand, manual camera (ISO, shutter, aperture, white balance all fixed), continuous artificial lighting with windows blocked, lights taped or weighted, plug-in power, remote trigger or interval timer. Full checklist in `references/lighting_lockdown.md`.
3. **Onion-skin and pose.** Enable onion skinning (ghost of previous frame over live view) in the capture app. Move in small increments, review with loop playback, reshoot bad frames instead of tolerating them. See `references/onion_skinning.md`.
4. **Shoot rigs visibly, remove in post.** Suspend puppets on wires or metal rigs, shoot a clean background plate of the empty set, erase rigs against the plate in post. Full procedure in `references/rig_removal.md`.
5. **Assemble.** Compile frames to video:
   `ffmpeg -framerate 24 -i frame_%04d.jpg -c:v libx264 -pix_fmt yuv420p out.mp4`

## Output Contract
- A finished clip at the planned duration +/- 5%, frames matching the plan from `bin/frame_calc.py`.
- No visible flicker between consecutive frames (check by scrubbing the timeline).
- No rig or support visible in the final clip.

## Operating Rules
1. Never shoot auto. One auto-metered frame can poison a whole sequence with a flicker that post cannot fix.
2. One change at a time per frame: move the puppet OR change nothing else. Hands, cables, and props stay out of the live view before every capture.
3. Reshoot the frame if the onion skin shows a jump; do not "fix it in post" unless it is a rig or dust, which are legitimately post problems.
4. The clean background plate must be shot with the exact camera position, focus, and lighting as the scene. Plate first or plate last, never mid-shoot after anything moved.
5. If the animator cannot see the difference between two consecutive frames in onion skin, the increment is too small to matter. Push it until the ghost shows motion, then capture.
6. Test the light for flicker before shooting: run a 60-frame time-lapse of the static set and step through it. If any frame shifts, change the light source before the real shoot.