Lighting & Look-dev

The execution model is in blender-core. Render settings are in blender-rendering. Full time-of-day, night and fog environments are in blender-time-of-day.

One call: presentation scene

scripts/turntable.py -- --objects Hero --rig studio --backdrop --frames 120 --lens 85
scripts/turntable.py -- --objects Hero --rig both --hdri //hdri/studio_small_09_2k.exr --hdri-strength 0.8

This builds a camera framed to the bounding sphere (on the narrower frame axis), a key/fill/rim area-light rig scaled to the asset, an optional 18%-grey cyclorama, and a pivot that orbits camera + lights + backdrop in a seamless loop. The asset itself isn't modified. Everything lives in the LD_Lookdev collection, and re-running replaces it. Set the render resolution before running, because framing depends on the aspect ratio.

Lighting recipes

• HDRI: Poly Haven (CC0) via the blender-mcp search_assets/import_asset, or ShaderNodeTexEnvironment + Mapping (Z rotation aligns the sun). Strength 0.5–1.5. Clamp sun hotspots if they cause fireflies.
• Light linking (4.0+, Cycles + EEVEE): set light_obj.light_linking.receiver_collection / blocker_collection (on the light object) to light only what you choose, like a hero rim that doesn't touch the backdrop. Portals: light.cycles.is_portal = True on area lights in window openings.
• Units: point/spot/area in Watts (a 60 W bulb ≈ point light 40–60 W in Blender), sun in W/m² (irradiance; 1000 ≈ physical midday, but use 3–10 with AgX for natural results), emission strength ≈ W/m². Keep lights physically plausible and control the overall image with exposure.
• Shadows: light size controls softness. A bigger, closer light is softer. Contact shadows should exist where objects touch, so check that nothing floats (blender-asset-qa ground_z).

Camera rules

• Focal length: 24–35 mm environments/interiors (keep verticals straight: camera level, or shift instead of tilting), 50 mm natural, 85–135 mm products and portraits (no distortion), 200 mm+ compressed telephoto.
• Composition: rule of thirds / centered symmetric for products, horizon off-center, leading lines, headroom. Show the silhouette (3/4 view at slight elevation 10–25°).
• DOF (cam.data.dof.use_dof, focus_object, aperture_fstop): f/2.8–5.6 for products at real scale. DOF depends on scale, so a wrong scene scale ruins it.
• Clip start/end tight around the subject (the script does this), which avoids precision artifacts.
• Sensor fit AUTO uses the larger axis. Portrait renders need framing on the width.

Look-dev procedure (material approval)

1. Neutral setup: --rig studio or a neutral HDRI, grey backdrop, Khronos PBR Neutral or AgX (pick one and keep it).
2. Add a calibration chart object if needed (a grey 18% sphere, a chrome sphere, a Macbeth chart) next to the asset.
3. Turntable at 24–30 fps, 120–240 frames, 85 mm. Render previews with render_batch.py --preset preview --format MP4.
4. Check the materials under 2–3 different HDRIs. A good PBR material holds up in all of them (blender-pbr-materials sanity checks).

Gotchas

• World lighting is invisible if world.node_tree has no Background → World Output link (the script ensures one).
• EEVEE needs use_raytracing for good reflections. Light probes (Volume/Sphere/Plane) still help static GI in interiors.
• Area lights that are too small and bright make fireflies in Cycles. Increase the size, decrease the power.
• A turntable that rotates the asset changes its transforms and animation data, which is why this rig orbits the camera instead.