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Desktop Radiance

To make decisions on the use of lighting and daylighting strategies and technologies, designers need to simulate their performance with respect to several quantitative and qualitative criteria related to comfort, energy, aesthetics, economics, etc. Radiance allows designers to accurately predict lighting and daylighting performance in spaces of arbitrary geometric complexity, as well as generate photometrically accurate renderings for qualitative assessment. Studies show that the Radiance is the most accurate daylighting simulation software available today.

The Radiance software was originally developed by researchers for research purposes. It was developed for use under the UNIX operating system and it lacks a user-friendly interface. It expects the description of building geometry, surface material properties, glazings properties, electric lighting luminaires geometry, position and photometric characteristics, etc., in an input file, using specific keywords and syntax. The input file is then processed by Radiance through a variety of UNIX commands, depending on the type of simulation desired. The requirement of a UNIX workstation and the complexity of using Radiance are the two major barriers in realizing a more widespread use of Radiance by building designers.

Screen shot of the Radiance lighting simulation and rendering software

Users can control the Radiance algorithms through a graphical user interface accessible from within AutoCAD.

Desktop Radiance is a Windows 95/98/NT software application, which facilitates the use of the Radiance lighting simulation and rendering software on personal computers. Desktop Radiance includes links to AutoCAD®, a popular commercial CAD software package, and electronic libraries of materials, glazings, electric lighting luminaires and furniture. Desktop Radiance users specify the geometry of the building surfaces using the AutoCAD software. They can then access all of Desktop Radiance functionality through a single "Radiance" menu in AutoCAD's menu bar. Through a graphical user interface, Desktop Radiance allows users to select materials from a library and attach them to the AutoCAD surfaces. They can also select and place glazings, as well as electric lighting luminaires and furniture items. Finally, they can place "cameras" and "light sensors" into the AutoCAD scene and request Radiance computations, specifying location, time of the year, sky condition, desired accuracy, etc.

Screen shot of multiple simulations

These two simulations show a comparison between two alternative lighting designs for the same space.

The Desktop Radiance software automatically prepares the Radiance input file and activates the Radiance algorithms for the computation of the desired output, which is also controlled through a graphical user interface. Through a "simulation manager," it supports easy management of multiple simulations, storing all input specifications and results into a project database. The Radiance output can be further manipulated to display quantitative and qualitative information in different ways, such as by superimposed illuminance/luminance iso-contours, false color displays and adjustment of images to account for the sensitivity and adaptation of the human eye.

The Desktop Radiance software is targeted to building designers that want to consider daylighting strategies and technologies for the design of commercial buildings. Its use is intended to contribute to the general market transformation efforts of the California Utilities. Beta versions of Desktop Radiance have been distributed to a large number of reviewers for comments and suggestions. It is available to the general public at Desktop Radiance web site. The initial version of the software is scheduled for release at the end of 1999.

— Konstantinos Papamichael

For more information, contact:

  • Konstantinos Papamichael
  • (510) 486-6854; fax (510) 486-4089

This research is supported by Pacific Gas & Electric Company (PG&E) through the California Institute for Energy Efficiency (CIEE).

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