Glare for External Environment

Hi everyone,

I have a question regarding metrics to measure glare potential, but for an external environment.

I was looking at the Honeybee example file for Glare Analysis and also this page here:…

The range of values in this page for imperceptible, perceptible, disturbing and intolerable glare make sense to me. My question is, however, are these ranges still applicable when you shift to an external environment? When the sun is out, the external environment is much brighter in comparison. And so I am getting DGP values closer to 0.7 or 0.8, which probably does not make sense because now everything is classified as glare. So, what metric would I use to figure out if, for example, a glass tower is actually creating glare for the people on the street? Should I be looking at the contrast among the luminance values in the scene? Or maybe just sunrays reflected directly by the building onto a specific spot?

Any thoughts would be helpful.



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Hi Saurabh,

There is no good answer for this. If you search in Radiance mailing list you should find Jan’s answer to a similar question on Radiance’s mailing list:

“Be aware, that DGP is just a measure for discomfort glare INSIDE a building. It does not include disability glare and is also no measure for discomfort glare OUTSIDE a building, where you have much higher adaptation levels.”

I would say a ray-tracing analysis can give you a good idea of potential issues but then how to calculate DGP values based on an image analysis is something that I can’t really comment on.

Thanks, Mostapha!

Hi Saurabh,

Have a look at this paper It might be of some interest for you


Thank you for the link. Looks like it might be useful.

Hi Saurabh,

Did you have any luck with this? If so would you be able to provide any advice?



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Hi Saurabh and Thomas,

FAA has a research about glare impact to flight pilot, here is one of paper,…

I have used their researches and results for the outdoor annual glare analysis.

You can use raytracing method and equations in that paper to calculate retinal irradiance, by which to determine the potential eye damage (Fig. 2 in the paper).

Hope this helps.


Hi Mingbo,

Did you use the forward raytracing compenent in Ladybug for this purpose? If so, how can you extract a solid angle so you can apply it in the formula?



Dear @MingboPeng,

I came across this theme.
Reading that you have done this type of analysis

I want to ask you, what kind of discomfort range did you use in the final result, since is not possible to use the standard DGP comfort range, for a outdoor potential glare.

Do you have any more information about it, where you can direct me?
Would really be appreciated.


Hello, the link of this paper cannot be opened, could you please send its article name or DOI number? Thank you