Blender Lighting Analysis

Separate light inference from light creation. Analyze first; mutate Blender only after the lighting hypothesis and gray-model prerequisites are recorded.

Suite Authority

Follow ../blender-production-router/references/production-protocol.md and ../blender-production-router/references/native-component-contract.md. The Router owns route, stage, budgets, rollback, and pauses. This skill owns illumination evidence, gray-light setup, and accountable light roles only; it may not move an accepted camera or restart analysis to hide geometry.

Evidence Order

1. Identify an object-ground contact and the corresponding shadow endpoint.
2. Infer horizontal Sun direction opposite the shadow vector.
3. Estimate Sun elevation from object height and shadow length when the receiving plane and scale are credible.
4. Infer source angular size or atmospheric softness from shadow penumbra.
5. Compare lit and unlit faces to estimate World/sky fill and bounce.
6. Identify visible practical sources, window projections, emissive surfaces, and occluders.
7. Record ambiguity and alternative hypotheses instead of inventing lights.

Read references/lighting-analysis.md before building a reference-matched rig. Validate the plan with scripts/validate_lighting_plan.py.

Gray-Light Gate

The first production-light pass may contain only:

• one Sun for the primary directional source;
• one low-intensity World/sky fill;
• accepted gray geometry;
• the review camera chosen by the user or task.

Match shadow direction, length, softness, lit/backlit relationship, dark-side visibility, and exposure before adding bounce or practical lights. Neutral topology-review lights are separate diagnostic tools and must not be mistaken for the production rig.

Lighting analysis may happen during Production Analysis, but the production gray-light pass may use only an accepted clay Blockout. Final lighting remains locked until formal topology, Structural Forms, Transition Forms, real bevels, and wireframe review pass.

Additional-Light Contract

Every added light records:

• ID and Blender object name;
• physical or photographic source;
• role;
• reference evidence;
• color/temperature and size rationale;
• affected region;
• what visible evidence is lost if the light is removed.

Add an Area, Point, Spot, emissive mesh, HDRI, bounce card, or volume contribution only when the Sun/World model cannot explain evidence. Delete or disable lights with no accountable role.

Hard Rules

• Do not use rim, fill, or colored lights to hide wrong geometry, missing bevels, or failed normals.
• Do not begin final lighting before Transition Forms and topology/wireframe gates pass.
• Do not use an HDRI as an unexplained replacement for source analysis.
• Do not accept a light setup because it makes primitive seams, missing transitions, or faceted curves less visible. Re-run neutral MatCap and reflective geometry review first.
• Do not multiply lights until one-source shadow logic has been tested.
• Do not change accepted geometry or camera merely to make the lighting plan easier.
• Do not treat emission color as proof of emitted intensity or real light transport.

Completion Gate

Require a passed gray-light comparison, documented Sun and World responsibilities, justified extra lights, stable exposure and color management, shadow evidence, dark-side readability, material response review, and a lighting_plan.json with no unresolved blocking source.