Cumulative Sky View Based

Hi all,

I’d like to request a cumulative sky for the view based recipe.
I couldn’t find it in LBT, and in Legacy the cumulative sky is not working together with the view based simulations.

I’ve seen this solved in radiance before (cant remember how) so it must definitely be possible.

It’s good for PV studies etc where one can render a whole city without setting up analysis grid etc manually.

pinging @mikkel <3 …

To be clear, are you are thinking of this component from HB-Legacy?


Yes exactly. To do a render and false color it to show PV potential.

also that one does not work with view based (in legacy)!

Oh, I thought you meant mixing this component with the new LBT components, which surely should not work. I admittedly have never used that component for renderings in Legacy. But I believe it should be possible to add it so you can render radiation maps with rpict in the new LBT. But I think it is better to hear @chris’s thoughts before I make any promises :slight_smile:

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Hm. I see what you are asking here. We’ll probably need @mostapha 's thoughts here to know the best way to implement this in LBT.

From what I understand, the cumulative radiation sky in Ladybug was something of a hack that relied on a .cal file to represent sky patches among other things. My intuition tells me that, if we were to support something like this in the LBT plugin, it would involve a view/image-based Daylight Coefficient simulation (since this is essentially how we support the HB Cumulative Radiation recipe in the LBT plugin). But I don’t know for sure. Mostapha will know.

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hello @chris @sarith

Would it be technically possible to run an annual image-based simulation that returns cumulative lux?

I’m trying to get the cumulative lux of a museum’s horizontal + vertical surfaces , in order to zone where art pieces should be placed to avoid decaying over time…

Hey @OlivierDambron ,

Why does it need to be an image-based simulation? Why not just run an annual daylight simulation and sum up the illuminance values on your artwork to get cumulative illuminance?

The interest is to test the walls to know where the artwork could be hung.
As soon as the spaces become more complex, testing all the walls poses a visualization problem, unless they all are laid out as elevations. Quite cumbersome.

A fish eye image-based analysis showing the cumulative lux per room would allow to visualize all walls+ floors at once.

Alternatively I could extract all interior surface and run a grid based annual daylight simulation to get the cumulative values.

I think you might be better off with a grid-based simulation for this case if you are mostly concerned about the incident illuminance on each wall.

The issue with doing a view-based analysis for this case is that the result in the image is going to be influenced by the reflectance of the wall that the light is bouncing off of before it gets to the view. It sounds like you don’t really care about this if the art is hanging on the wall. Is that correct?

Quite sure it’s possible through vwviews(?), Rcontrib and genskymtx combo. Or something similar.

Or with a custom Reinhart sky where each sky patch has the cumulative values. Should be possible technically.

Alstan shows it in these slides, perhaps via DAYSIM.

Yea, it’s technically possible with the “HoneybeePlus_DC Image-based Recipe”, which uses rcontrib under the hood. Or you could use the Honeybee Legacy Cumulative Sky with an Image-based simulation.

But these are still NOT the analyses that I would recommend for this situation. An annual daylight or annual irradiance simulation is going to be much more focused on what you care about (not being influenced by the reflection off walls). Plus it will actually model the direct sun correctly, which won’t be the case for those older methods that rely entirely on daylight coefficients.

Great thanks Chris. You are completely right in the flaws of the discretized sky and the lack of precise sun position. I guess reflections could be avoided with -ab 1?

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