Hi All,

I am new to grasshopper interface and stuck at the stage. I am trying to get the hourly illuminance values for a set of grid nodes via grasshopper interface. I have defined the grid nodes at a work plane (+2.5 feet) level and set the simulation type to climate based and with ambient bounce to zero in order to determine times of the year the sensor point is direct sunlight. Under the output settings I have checked the Hourly illuminance.

After running the daylight simulation via grasshopper, when I connect the Hourly illuminance output to a panel, I can only view data for one of the sensor point and not sure which point it is for.


My question is:

1)      How can to map each grid point and it associated illuminance values using grasshopper component?

2)      How to get csv or text format output of the data corresponding to the each sensor point?

I plan to do conditional testing for every hour for each sensor point either via grasshopper or using excel.

Any suggestion or pointers would be very helpful.

Please see the attached zip file containing   Rhino model and Grasshopper file.




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Hi Aditya,

The Hourly Illuminance output should contain the hourly data for each input node.  The trick is that the data is structured into a tree, where each "branch" represents one node.  In fact, if you mouse over the output on the DIVA Daylight component, you will see what the structure of this tree looks like:

There are 36 branches, labeled {0} through {35}, one for each node.  Each branch contains 8760 hourly illuminance values, one for each hr of the year.  If you pass this data tree onto another Grasshopper component, that component will do its operations independently on each branch.  For example, of you pass the output onto Grasshopper's "List Item" component, you will get 36 numbers, representing the 0th item of each of the 36 branches (the default item index, until you specify differently, turns out to be zero).  I'd suggest checking out Andrew Payne and Rajaa Issa's helpful Grasshopper Primer to familiarize yourself with data trees and other GH topics.

In the meantime, if you're more familiar with Excel, you can actually open the illuminance file directly as a space-delimited file:


Using Grasshopper, though, you could visualize your conditional test using a slider to pick the hour of the year, and then a color preview to paint your nodes according to their illuminance value.  See attached.




Thanks for the great! tip for visualizing conditional test and for pointing me to towards the Grasshopper primer document. I finally figured out how to cycle through the tree branch, I did this by using a  tree branch component and number slider to retrieve  the 8760 data for each of the 36 branch or sensor points.

Appreciate your prompt response.


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