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What this validation covers

Lumen Pro 2, the IES-based photometric lighting add-on for Blender, was validated against the analytical reference values of CIE 171:2006 — “Test cases to assess the accuracy of lighting computer programs” (the CIE standard used worldwide to verify lighting software). Lumen Pro handles the IES photometric data, the point and area light setups and the real-time measurement probes; the lighting calculation itself is performed by the Blender Cycles renderer. Eleven test cases are covered, split into two groups:

Artificial lighting

• 5.2 — simulation of point light sources (direct illuminance under a photometric distribution file):
  • Diffuse (Lambertian) photometry I(θ) = 1000 · cos(θ) cd
  • Batwing photometry (ERCO Quintessence Square, LED 12 W)
• 5.3 — simulation of area light sources (1×1 m Lambertian area light, diffuse photometry)

Daylighting

• 5.9 — daylight factor under a 1×1 m and a 4×4 m roof opening (CIE general sky type 1)
• 5.10 — the same roof openings fitted with glazing (transmission 0.88)
• 5.11 — daylight factor through a 2×1 m and a fully-open 4×3 m vertical facade opening
• 5.12 — the same vertical facade openings fitted with 6 mm glazing (transmission 0.88)

All calculations use CIE general sky type 1 (overcast sky) for daylighting and a 100% white diffuse BSDF (0 roughness) on the internal surfaces. The illuminance / daylight factor is calculated at measurement points and compared with the analytical reference values.

Test overview

Test	Source	Photometry
5.2	IES point light at 3 m	Diffuse (Lambertian) 1000·cos(θ)
5.2	IES point light at 3 m	Batwing (ERCO Quintessence Square)
5.3	1×1 m area light (ceiling center)	Diffuse (Lambertian) 1000 cd
5.9.3.1	1×1 m roof opening	Daylight factor (%)
5.9.3.2	4×4 m roof opening	Daylight factor (%)
5.10.1.1	1×1 m roof opening	glazing (T 0.88)
5.10.1.2	4×4 m roof opening	glazing (T 0.88)
5.11.3.1	2×1 m vertical facade opening	Daylight factor (%)
5.11.3.2	4×3 m vertical facade opening	Daylight factor (%)
5.12.3.1	2×1 m vertical facade opening	6 mm glazing (T 0.88)
5.12.3.2	4×3 m vertical facade opening	6 mm glazing (T 0.88)

CIE 171 validation result

The calculated illuminance and daylight factors closely match the analytical reference values of CIE 171:2006 across all test cases (within a fraction of a percent for the artificial lighting tests). The full report contains the per-point comparison tables, the accuracy indicators (MAE, RMSE, relative deviation) and the reference-versus-Lumen graphs for every test.