| Abstract | This article compares daylight simulation results generated with two simulation programs, Autodesk® 3ds Max® Design 2009 (3ds Max Design) and Daysim 3.0 (Daysim), to indoor illuminance measurements in a sidelit space. The sidelit space was in a single location, but was configured with five fenestration and glazing options, and operated under a variety of sky conditions. The measurements form a set of 'daylighting test cases' that were recently developed to evaluate the simulation capabilities and limitations of different daylight simulation programs. Both 3ds Max Design and Daysim were given external direct and diffuse irradiances as simulation input, from which the programs predicted indoor illuminances on a grid of upward facing work plane sensors and downward facing ceiling sensors. 3ds Max Design is based on ExposureTM technology, a lighting analysis module that includes a 'shader' of the Perez sky model and that uses the mental ray® raytracer for the global illumination calculation. Daysim also uses the Perez sky model and is based on the Radiance backward raytracer combined with a daylight coefficient approach. The comparison of both programs with measurements demonstrated that 3ds Max Design simulated indoor illuminances for the daylighting test cases with reliability comparable to Daysim. Most mean bias errors and root mean square errors were in the range of those reported in earlier validation studies: both programs succeeded in reproducing measurements for a sidelit space with and without a lightshelf. While 3ds Max Design consistently underestimated the incoming light flux going through a translucent panel, Daysim results were lower than measurements for the internal venetian blind test case. The results suggest that the accuracy of both programs is sufficient for typical daylighting design investigations of spaces with complexity comparable to the five daylighting test cases. |
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