Sy = sqrt(1 + Y 2) = 1.1180 Vertical Points (E – F) Table 19 of CIE 171:2006 is incorrect, likely because incorrect geometry was used for the calculations.
We can again use form factor algebra to determine: We can then use form factor algebra to determine:įor the vertical surface S 1‑v measurements, the geometric relationships are: For the horizontal surface S 1‑hz measurements, the geometric relationships are:Īnd the configuration factor C is given by: To validate the values presented in Table 19, it is necessary to calculate the configuration factors between the measurement point and the unobstructed portion of S 2. This is equal to the configuration factor between the measurement point and the unobstructed portion of S 2. 1.1 Analytical ReferenceĪs noted in Section 5.7.3, “To enable comparison between the simulation results and the analytical reference independently from the illuminance value over S 2 or from its surface reflectance, the reference values are presented under the form of E / E v The following independent analysis indicates that the values presented in Table 19 are incorrect. The derivation of Table 19 is not explained in CIE 171, but it was presumably determined using form factor analysis. The objective of Test Case 5.7, “Diffuse reflections with internal obstructions,” is to “verify the capability of a program to simulate the influence of an obstruction to diffuse illumination.” Hopefully, this information will ease the pain and suffering of anyone undertaking the work of validating a lighting design and analysis program against this document. Unfortunately, the CIE has yet to publish errata for CIE 171:2006, and there are currently no plans to do so.Īs a service to the lighting industry, then, the following is a complete list of known errors in CIE 171:2006. (The correct terminology is “validated.”) The CIE Central Bureau has confirmed (Paul 2013) that it has requested these companies not to use the phrases “certified by” or “certified against” CIE 171:2006. NOTE: Some companies have stated that their products have been “certified” by the Ecole Nationale des Travaux Publics de l’Etat (ENTPE). To date, there have been at least fifteen lighting design and analysis programs that have been validated against some or all of the CIE 171:2006 test cases, including: Manufacturer Understanding and documenting these errors is important. Further errors became evident during the preparation of a graduate thesis (Osborne 2012), and more during a recent validation study (Dau 2016). The first and most important of these errors became apparent a year later when one of the first validations of a commercial lighting design and analysis program was conducted (Dau 2007). It is therefore understandable that there were at least a few errors in the final report. The second type is obtained through experimental measurements, where the scenario and the protocol are defined in a manner that minimizes the uncertainties associated with the measurements.Īs one of the 24 members of CIE Technical 3-33 that wrote the report (mostly as a technical editor and reviewer), and also as a member of the IES Computer Committee that spent a decade attempting to write a similar document, I can attest that it was a monumental task. The first is associated with theoretical scenarios that avoid uncertainties in the reference values. Two types of reference data are used: data based on analytical calculation and data based on experimental measurements. To apply this approach, a suite of test cases has been designed where each test case highlights a given aspect of the lighting simulation domain and is associated with the related reference data. A validation approach is therefore presented based on the concept of separately testing the different aspects of light propagation. The objective of this report is to help lighting program users and developers assess the accuracy of lighting computer programs and to identify their weaknesses. In 2006, the Commission International de l’Eclairage (CIE) published CIE 171:2006, Test Cases to Assess the Accuracy of Lighting Computer Programs.
Relux 2008 software#
[Please send all comments to 16/07/08 – Added Optis SPEOS to list of validated (not “certified”) software products and Test Case 5.11 analysis. Eng., FIES Senior Scientist, Lighting Analysts Inc.
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