Lighting Design Simulation Programs Comparison_

The need for architects and lighting designers to attain optimal lighting solutions is met by using lighting simulation software. However, these types of software do not provide visually compelling outputs when compared to visualization software. Since the scope of this research is based on visual results, it was imperative that we investigate their performance, and decide if visualization software would be appropriate to consider. To this end we compared the results of specific lighting design tasks, in order to determine the accuracy of the output results. While some comparative studies have been made to compare purely lighting design software[1] [2] [3], no research exists that evaluates the results between these kinds of software - such as Relux and Dialux - and visualization programs, such as 3D Studio Max. The later focuses mainly on three-dimensional modeling and rendering, but it also features lighting calculation algorithms as a secondary feature.

The scope of this comparison is 1) to investigate to which extent visualization programs can present accurate lighting calculations and 2) whether their results are close to the verified output of the lighting industry standard software. The software programs used for comparison were Relux, Dialux and 3D Studio Max. For the comparison simulation, a typical vertical surface measuring 5m wide and 10m high was modeled, as well as a part of a horizontal surface (ceiling/balcony) to identify light attenuation on the upper horizontal plane (Fig. 1). The model was simulated on its own with no surrounding objects so as to eliminate any unwanted reflections. A variety of outdoor luminaries was used to uplight the surfaces with the main consideration being that the luminaire manufacturer provided an IES file that could be used in all three software applications. Since this part is an ongoing research, from the luminaires tested we selected the iPro from iGuzzini model number BX15. The main feature, of this selection, lies in the fact that it consists of C.o.B LED technology[4] which allows us to have a uniform diffusion of light as the light source is referred to as a spot. Other important features of the luminaire are shown in the table below.

Source: Data Adapted from www.iguzzini.com.

Preliminary results show differences in illuminance levels and light distribution between the two sets of computer applications. The results vary in both the vertical and horizontal axes as shown in Figures 2 and 3. In general it seems that visualization software calculates on average 20% more illumination levels on the vertical axis, but despite this difference they have a very similar linear distribution. In this case the average correlation coefficient for 30 pairs of data between the two set of programs is 0.90, which indicates a 99.9% correlation.

On the horizontal axis there is an average of 35% more illumination levels on the horizontal axis, but the linear distribution has a similarly high correlation since the average correlation coefficient for 30 pairs of data between the two set of programs is 0.66. Due to the fact that in the present research distribution is the dominant factor to assess a lighting scenario, the distribution correlation of 99.9% means that visualization software can be used to evaluate images concerning lighting calculations. In short, the images from 3D Studio Max are brighter and have a higher contrast than images produced by Relux or Dialux, but the distribution of light is almost the same.Above we examined the potential accuracy from a visualization program that produces photorealistic images, by comparing it to lighting design software whose results we consider to be as accurate as possible. Since the goal of this research is to create a visual toolset which will be represented by photorealistic images, the results of the above study confirm that the 3D Studio Max can yield the visual result, on which the methodology will be based.