Building Energy Software Tools
Formerly hosted by US Dept. of Energy    

Radiance

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Radiance uses a light-backwards Monte Carlo ray tracing method with irradiance caching for efficiency. A photon-mapping capability was recently added to handle caustics and difficult daylighting situations.

The primary advantage of Radiance over simpler lighting calculation and rendering tools is that there are few limitations on the geometry or the materials that may be simulated. Radiance is used by architects and engineers to predict illumination, visual quality and appearance of innovative design spaces, and by researchers to evaluate new lighting and daylighting technologies. Advanced annual simulation capabilities are included as well.

Expertise Required: 

High level of computer literacy required. Familiarity with command-line interfaces and Unix toolbox model is assumed.

Audience: 

Daylighting, lighting, and architectural designers.

Input: 

Input files specify the scene geometry, materials, luminaires,time, date and sky conditions (for daylight calculations). A number of third-party developers have created interfaces to produce the needed input for Radiance, including OpenStudio and DIVA for Rhino. Translators may also be found for popular CAD tools such as SketchUp.

Output: 

Calculated values include spectral radiance (ie. luminance + color), irradiance (illuminance + color) and glare indices. Luminance and illuminance values, plots and contours, visual comfort levels, photograph-quality images and video animations.

Strengths: 

Physical accuracy in a graphics rendering package, reliability and source code availability; arbitrary surface geometry and reflectance properties. Ability to calculate and accept arbitrary measured BSDFs (bidirectional scattering distribution functions) and complex fenestration and perform efficient annual simulations.

Country: 
United States
Major Capabilities: 
Parametrics and Optimization
Weather Data and Climate Analysis
Lighting Simulation
Language: 
English
Platform: 
Linux
Windows
Mac OS X
Pricing: 
Free
Help and Support: 
Free Email Support
Last Software Update: 
18 September 2015
Last Entry Update: 
17 November 2015
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