Image Generation: 
Daylighting and Lighting

Capabilities and Services

We can develop computer-generated images of spaces within and around buildings, especially  images that are not just artistically pleasing but also portray visual reality up to the limits of currently available software technology.

TDG has developed the interactive website www.EcoAdvisor.com which provides guidance on daylighting design for buildings. One objective of this website is to demonstrate how daylighting and lighting design can improve the visual quality of spaces in buildings. To achieve this objective, we use the Radiance and Lightscape (3-D Studio Viz) software program to generate many images of typical office spaces.
 

Radiance:  is quite good at developing reasonably accurate images of spaces that incorporate both daylighting and electric lighting. However, it has been developed via a research effort at a national laboratory and is not a commercial production tool. Indeed, it is quite difficult to use and the documentation for its use is often both incomplete and oblique. Also, the most flexible version of it runs under Linux but not Windows, and we have set up a major Linux-based system capability for Radiance using a number of dual-boot computers.
 

The top picture on the right shows a 2-person office with low reflectance surfaces. The same space in the bottom picture is much brighter as a result of increasing the reflectance of ceiling, walls, partition, desktops, and floor. The lighting system was not changed.

Lightscape has recently become embedded in 3-D Studio Viz.

Parametric 3-D models of typical spaces: We have also developed object-oriented parametric 3-D models of typical spaces. We use scripts to generate images with variations in space features such as:

• Window head height,

• glazing type

• External shading

• Venetian blinds at various angles

• Partition height and opacity

• Electric lighting system options

• Presence of absence of atria or skylights.

To date we have developed such models for typical open office and conference room spaces.

The daytime conference room picture at the right combines daylight with electric lighting from the pendant fixture, two down lights on the far wall and within the credenza enclosure. The night version is the same view of the space but with fewer furniture objects shown and just 2 types of lighting on. 

In general, the scripts control the following sequence activities:

• A set of parametric images is defined with variables set in a text file extracted from an Excel file.

• A Linux script allocates all images to available processors.

• As each processor generates Radiance images, a Linux script “harvests” them by moving the files to a large hard-drive on a single workstation. We typically generate images in high resolution and save the images in those storage-intense resolutions.

• After all processing is completed then the Radiance images undergo appropriate post-processing.

• Then, since most images are destined for web use, the output files are converted and compressed to JPG format.

• Finally, the files are moved to the TDG server until they are uploaded to the appropriate website location.

We have developed file-naming protocols to track the large volume of input and output files that are associated with the generated images.

We also use scripts to generate images that show photometric results, such as illumination levels throughout a  space. Several images on the right of floor plans of a large open office space show increasing usable daylight penetration as window head height increases and finally as an atrium is added. Daylight availability for different purposes is assumed as follows:

• DL for office tasks if footcandles > 50 (lux > 500).

• DL for ambient light if footcandles > 20 (lux > 200).

• Inadequate DL if footcandles < 20 (lux < 500).

You can interactively explore the results of this capability at our www.EcoAdvisor.com website under daylighting > distribution > geometry / or windows / or interiors.

In developing Radiance and Lightscape images for various projects we have also worked with LBNL, Michael Woodcox, and Vincent BriseBois.

In applying daylighting and lighting design concepts we have used Hayden McKay Lighting Design and Nancy Clanton of Clanton Associates.

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Project Experience

Highland Pool is a good example of our project experience developing such images.  

Highland is an existing indoor pool in New Mexico had a dark ceiling, and continuous window-walls on north and south with translucent white plastic garage doors. The windows were not shaded and the glare and contrast were so great that it was difficult for life guards to see into the pool. TDG built a 3-D model in AutoCAD, added material and luminaires using Radiance, and developed incremental parametric versions that included:

• light colored ceiling
• screens for the roof skylights
• external shading to reduce the brightness of the outside concrete on north and south.
• change windows from translucent to clear or tinted to reduce glare.
• explore different electric lighting options, with a preference for indirect systems.

Combinations of the above measures substantially reduced glare from the outside and excess contrast inside. This greatly improved the visual quality within the space.

We developed these Radiance images for the Weidt Group in support of their work for their client

Last edited 28 July 05