VELUX Daylight Visualizer 2 calculations have been validated against CIE 171:2006,Test Cases to Assess the Accuracy of Lightning Computer Program. The evaluation was performed in collaboration with ENTPE, l'Ecole Nationale des Travaux Publics de l'Etat in France.
VELUX Daylight Visualizer 2 is a software tool dedicated to daylighting design and analysis. It simulates daylight transport in buildings to aid professionals by predicting and documenting daylight levels and appearance of a space prior to realization of the building design. The software permit generation of 3D models in which roof and facade windows are freely inserted. Other settings include the location and orientation of the models, the date and time of the simulation, as well as the sky type (from clear to overcast). In addition to photorealistic rendering, the simulation output includes luminance, illuminance and daylight factor maps.
Like any light transport software, the critical question is whether VELUX Daylight Visualizer 2 produces trustable simulations the user can be confident in. A key point to answer this question is to assess the software capability to simulate the light transport in a physically correct way.
The objective of this report is to present an overview about the results of the assessment VELUX Daylight Visualizer 2 against test cases 5.4 – 5.5 – 5.6 – 5.7 – 5.9 – 5.10 – 5.11 – 5.12 – 5.13 – 5.14 (Test Cases to Assess the Accuracy of Lightning Computer Program). The original CIE document the current study is based on is:
CIE 171:2006 report, 2006, ISBN 978 3 901906 47 3
An abstract of the CIE document is available at: http://www.cie.co.at/publ/abst/171-06.html and the full document can be bought at: http://www.techstreet.com/ciegate.tmpl.
In this report, we present an overview table, depicting the average error observed with respect to the CIE 171:2006 analytical reference, for custom settings of VELUX Daylight Visualizer 2. We indicate whether the different test cases are passed, based on the ENTPE – DGCB / CNRS expertise in lighting design.
VELUX Daylight Visualizer 2 can accurately predict daylight levels and appearance of a space lit with natural light, prior to realization of the building design.
VELUX Daylight Visualizer 2 passed the CIE 171:2006 test cases dedicated to natural lighting. For the custom setting, VELUX Daylight Visualizer 2 simulates the following aspects of natural light transport with a maximal error lower than 5.13 %, and an average error lower than 1.29 %:
• Luminous flux conservation
• Directional transmittance of clear glass
• Light reflection over diffuse surfaces
• Diffuse reflection with internal obstructions
• Sky component for a roof unglazed opening for CIE sky types 1-15
• Sky component under a roof glazed opening for CIE sky types 1-15
• Sky component and external reflected component for a façade unglazed opening for CIE sky types 1-15
• Sky component and external reflected component for a façade glazed opening for CIE sky types 1-15
• Sky component and external reflected component for an unglazed façade opening with a continuous horizontal mask for CIE sky types 1-15
• Sky component and external reflected component for an unglazed façade opening with a continuous vertical mask for CIE sky types 1-15