Composition Quality Checker

composition-quality-checker

Purpose

Run a focused pass/warn/fail check on the camera + framing setup against composition rules (rule of thirds, headroom, lead room, negative space, visual hierarchy) — without expanding into material or lighting concerns.

Quick start

• read camera FOV, position, target, lens
• read framing intent from brief (close-up / medium / wide / hero card)
• check rule of thirds, subject placement, headroom, lead room
• check negative space and visual hierarchy
• emit verdicts + a top-line status

When to use

• before render
• after a camera change request
• as a sub-check during full quality review
• when a render "feels off" but lighting and materials check out

When not to use

• material validation (use material-quality-checker)
• lighting validation (use lighting-quality-checker)
• broad pass/warn/fail readiness (use blender-scene-quality-checker)
• to fix camera (this skill validates, it does not edit)

Trigger phrases

• "is the framing okay"
• "check composition"
• "subject feels off-center"
• "too much negative space"

Prerequisites / readiness

• camera setup known (FOV / focal length / position / target / lens)
• framing intent known (from brief)
• subject identified

Input schema

Required inputs

| Input | Why it is required | |---|---| | Camera setup | Anchors composition checks | | Framing intent | Determines applicable rules (close-up vs hero card vs wide) | | Subject identification | Determines what is "the subject" for placement rules |

Optional inputs

| Input | Use | |---|---| | Aspect ratio | Affects framing rules (16:9 vs 1:1 vs 9:16) | | Reference image | Allows cross-check |

Assumptions to confirm

• Render aspect ratio is known and stable.
• "Subject" is unambiguous in the brief.
• Camera is locked (or animated path is documented).

Output schema

Primary output

A composition verdict table covering: rule of thirds, subject placement, headroom, lead room, negative space balance, visual hierarchy, depth cues, lens / FOV plausibility — each with verdict + notes.

Secondary output

• top-line status (Pass / Warn / Fail)
• worst-offender highlighting
• aspect-ratio match

Evidence / caveat output

Runtime status: Not Run | Attempted | Produced | Verified | Failed | Blocked / Not Run
Artifact status: Not Run | Not Produced | Produced | Verified | Failed
Evidence used: 
Limitations: 

Required laws

• ../../laws/evidence-before-done.md
• ../../laws/non-blender-user-language.md
• ../../laws/no-arbitrary-python-interface.md
• ../../laws/official-runtime-only.md

Official runtime boundary

This skill validates camera plans or measured scene snapshots only. It never moves the camera, runs Blender, or renders. Use measured camera description (plan output, runtime tool snapshot).

Operating procedure

1. Read camera setup and framing intent.
2. Apply rule of thirds checks (see references/composition-rules.md).
3. Apply subject placement rule per intent.
4. Apply headroom / lead room rules.
5. Apply negative space and hierarchy checks.
6. Apply lens / FOV plausibility rules.
7. Cross-check with aspect ratio.
8. Assign per-row verdicts; collect notes.
9. Compute top-line status; highlight worst offenders.
10. Hand off to blender-scene-quality-checker (broader review) or blender-composition-camera-planner (re-plan).

Decision tree

Subject dead-center in 16:9 hero card?
  → Pass for symmetric hero; Warn for documentary/editorial mood
Subject in dead corner?
  → Fail unless intentional asymmetry called out in brief
Headroom > 30% of frame for portrait?
  → Warn (too much empty space above)
Headroom 0% (subject's head touching top)?
  → Fail
Lead room missing for moving subject?
  → Fail (subject "pressed against" frame)
Negative space carrying intentional weight?
  → Pass; verify with brief
FOV 
Framing intent: 

| Check | Verdict | Notes |
|---|---|---|
| Rule of thirds | Pass/Warn/Fail | |
| Subject placement | Pass/Warn/Fail | |
| Headroom | Pass/Warn/Fail | |
| Lead room | Pass/Warn/Fail/N-A | |
| Negative space | Pass/Warn/Fail | |
| Hierarchy | Pass/Warn/Fail | |
| Lens / FOV plausibility | Pass/Warn/Fail | |

Top-line: 
Worst offenders: 
Limitations: 
Next: blender-scene-quality-checker / blender-composition-camera-planner

Anti-patterns

• Editing the camera inside this skill.
• Inventing values.
• Marking Verified without preview.
• Mixing material / lighting checks here.

Cross-skill handoff

• Broad readiness review → ../blender-scene-quality-checker/SKILL.md
• Material validation → ../material-quality-checker/SKILL.md
• Lighting validation → ../lighting-quality-checker/SKILL.md
• Composition re-plan → ../blender-composition-camera-planner/SKILL.md

Non-goals

• Move the camera.
• Generate composition recipes.
• Replace blender-scene-quality-checker.
• Run Blender.

References

• references/composition-rules.md
• references/headroom-leadroom-rules.md
• references/aspect-ratio-rules.md
• ../../laws/evidence-before-done.md
• ../../docs/skill-system.md

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: ThanhNguyxnOrg
• Source: ThanhNguyxnOrg/blendops
• License: MIT
• Homepage: https://github.com/ThanhNguyxnOrg/blendops

Install and usage instructions live in the source repository linked above.