Hello everybody,

I'm trying to simulate, in a climate based calculation, a detailed dynamic shading which activates when the extarnal sensor is hit by ONLY direct sunlught(even very low) and the sun azimuth and zenith angles are in a certain range.

I found that the automated glare control is suitable for that, but the problem is that the threshold I can specify includes the contribution of both direct sunlight and diffuse skylight, while my system works only with the direct sunlight.

Is there a right way I can set this threshold to pursue my goal?

I mean, is there a value for this threshold i can use being sure that above that the sensor is surely hit by sunlight and not instead i'm in presence of a bright cloudy sky?

If not are there any other methods to simulate what I'm looking for?

Thanks in advance for your help



Don't know if it helps, but the location is Abu Dhabi

Tags: detailed, diffuse, direct, dynamic, setting, shading, skylight, sunlight, threshold

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Hi Luigi,

I can't think of a way to separate out the diffuse from the direct component in an easy way just through the GUI. That being said, I wonder how that system would even achieve it in reality- a photosensor wouldn't know either whether the sun is out or not, but probably just illuminance. Just my 2c,


Hi max, 

thanks for your answer. Actually we're not talking about a photosensor, but of a mechanic actuator which reacts only to direct light. It's for this reason that I posted this question.

Anyway, if you  have any suggestions I'd be glad to hear them.



Hi Luigi,

If you just need the resulting shading schedule and not the actual daylight distribution inside (an unlikely thing, I know), you can set the ambient bounces (-ab) value to 0 for your simulation. This will ensure that only direct sunlight reaches the sensor. If you need to pair that with the resulting distribution of light in the space, as I imagine you do, then the only option for the time being is to manually write your own algorithm to piece together the annual illuminance files based on the shading schedule from the 0 ambient bounce simulation.



Hi Alstan,

thanks for your answer. If i understood well the -ab 0 takes in account only direct sunlight while ab > 0 calculates also the amount of diffuse. I should then run three different simulations:one with ab set to 0 (S1), one with the ab set to the value I want and the shading system opened (S2) and one with the shading system closed (S3). Then i create a script that when the illuminance values on the .ILL file of the S1 are 0 takes the same lines from the .ILL file of the S2, otherwise, when the illuminance is higher than 0 takes instead the lines from the .ILL file S3.

Would this be correct? 

Hi Luigi,

This is the way I put it in one of my course slides,

An ab of 0 only sees direct light sources (the sun) but not the diffuse sky. An ab of 1 will see the sun, its first reflection and visible diffuse light sources. An ab of 2 will see the sun, its first two reflections, visible diffuse light sources and their first reflection.

Your idea of the three .ill files would work just fine. The resulting combined ill file considering your shading device can also be used to generate annual metrics such as daylight autonomy and useful daylight illuminance.



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