How validated is Radiance?

A co-worker of mine, who is more familiar with AGi32, has recently asked me if I knew how “validated” Radiance was. He mentioned that there was a series of CIE test cases, and that actually some of the test cases were not quite correct. I replied that to my knowledge, the Radiance community was very committed to validation and photometric correctness, but I didn’t know exactly what the current “state” was, or where I could see what was well established, and where the known shortcomings were.

I thought maybe some of the Radiance folks here could help answer :slight_smile:

The 1995 validation under measured sky luminance patterns is generally considered a benchmark, at least for ordinary glazing. It is described in exhaustive (exhausting?) detail here:

Related papers include:

J. Mardaljevic. Validation of a lighting simulation program under real sky conditions. Lighting Research and Technology, 27(4):181–188, 12 1995.

J. Mardaljevic. The BRE-IDMP dataset: a new benchmark for the validation of illuminance prediction techniques. Lighting Research and Technology, 33(2):117–134, 2001.

This paper describes the confounding factors that often come into play when attempting ‘real world’ validation:

J. Mardaljevic. Verification of program accuracy for illuminance modelling: Assumptions, methodology and an examination of conflicting findings. Lighting Research and Technology, 36(3):217–239, 2004.

And, of course, there have been other validation studies, e.g:

C. F. Reinhart and M. Andersen. Development and validation of a Radiance model for a translucent panel. Energy and Buildings, 38(7):890 – 904, 2006.

I don’t hold much store by the CIE test cases since they are so idealised. The reason Radiance performed poorly in one of them is because the scenario was effectively a highly reflective integrating sphere. Radiance could be tweaked to solve for this, but it would require a recompile with the AVGREFL macro redefined to, say, 0.95 IIRC (not something you’d want for any real-world application). That is in addition to the errors spotted by Ian Ashdown.


John Mardaljevic PhD FSLL FIBPSA
Professor of Building Daylight Modelling
School of Architecture, Building & Civil Engineering
Loughborough University
LE11 3TU, UK

Tel: +44 1509 222630 (Direct)

Aperture-Based Daylight Modelling: a new direction for daylight planning

Personal daylighting website:

1 Like

Hi Dion,

concerning the validation against the CIE cases I did some work during my
PhD. Parts of it were presented at the Radiance Workshop 2008
More details are included in my PhD thesis here
I also mentioned the errors in the CIE publication and re-calculated the
correct analytical references.


1 Like

I can offer an additional 28 studies that have validated Radiance, cited in my thesis: Validated Interactive Daylighting Analysis for Architectural Design. See page 28, section 2.2.3.


1 Like