Lighting Modeling

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Building Performance Simulation

Acoustics Modeling Energy Modeling Hygrothermal Modeling Ventilation Modeling Fire Safety Modeling Lighting Modeling

Lighting Modeling

The lighting conditions represent a key-aspect for the indoor environmental quality. The sustainability protocols currently in use promote the daylighting strategies due to eventual energy savings and the high spectral frequency compared with artificial lighting. In order to guarantee optimum lighting conditions. Even during the early design stage, it is important to evaluate the natural and artificial lighting conditions, which assist in identifying possible weak points where light lacks or exceeds. On the other side, lighting simulation allows us to evaluate the efficiency of shading devices and their effects on lighting conditions. Lighting modeling helps to optimize a performance of a system and makes an analysis of the system's visual and non-visual lighting aspects.

Lighting Modeling Methodology

By determination of scene, area of interest, space usage, and sky model, the model is built. Then, daylighting simulation engine starts the calculations by one of the following main methodologies:

Lighting Modeling Applications

Evaluating space lighting levels and compliance with standards,
Designing, comparing, and assessing shading devices,
Evaluating indoor visual comfort,
and designing energy-efficient lighting devices.

Lighting Modeling Tools

DIALux, Climate Studio, ALFA, Radiance, RELux, and DesignBuilder are some of the most popular lighting modeling tools.

BRE Split Flux,
Radiosity,
and Raytracing.

The BRE split flux or protractor method, developed at a research institution that is now called the British Building Research Establishment (BRE), only models diffuse sky conditions for daylight factor calculations, and splits internal daylighting levels into three components: a Sky Component (SC), an Externally Reflected Component (ERC), and an Internally Reflected Component (IRC).
Originally developed to solve problems involving radiative heat transfer between surfaces based on form factors, the radiosity method has also been applied in computer graphics to calculate illuminance levels due to electric lighting or daylight since 1980s. In radiosity, each surface is treated as a perfectly diffuse reflector with a constant luminance so that the radiation exchange between two surfaces can be described by a single number, which depends on the reflective properties of the surfaces as well as the overall scene geometry. To calculate the indoor luminance distribution in a room due to daylight, the incoming luminous flux through all non-opaque parts of the building envelope is set equal to the available flux within the building.

The basic approach of raytracing is to simulate individual, representative light rays in a scene and to extrapolate the overall luminous distribution of the scene from the available lighting information. Forward raytracing (rays traveling from a light source) is generally used to analyze the interaction of light with individual components such as a luminaire or venetian blinds. Whereas, for more complex scenes such as a whole neighborhood, light backward raytracing is generally used. In backward raytracing, rays are emitted from the point of interest and traced backwards until they either hit a light source, such as the sun or celestial hemisphere, or another object.

Due to the superiority of the radiosity and raytracing methods in comparison with the BRE Split Flux method, most lighting simulation tools use the former approaches which are also adopted by artificial lighting simulation tools.