From the generated bat file....

I see that it runs gen_dc, ds_illumn, and gen_directsunlight

Does this mean it runs an rtrace at everytime in the schedule (for example every hour from 8-6) and build the standard octtree similar to point in time lumiance first or are these 2 entirely different processes under the hood.

I did not see an oct file for the climate-based analysis.

Or is it randomly sampling some times throughout the weather file and year and not running an rtrace every hour....?

I was wondering when I was tweaking the -ab for ambient bounce parameter in the Radiance Parameters if that was have an affect in Climate-Based, since I see it makes a direct impact in Point-in-time...

Tags: daylighting, daysim, radiance

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Hi Renna,

The climate-based simulations run a modified version of rtrace, rtrace_dc (which is operated by gen_dc). The DC stands for daylight coefficient. It basically calculates the contribution of 145 diffuse sky patches and ~65 direct solar positions relative to each sensor node in your simulation. Once these daylight coefficients are calculated, its easy for the software (ds_illum) to go back through and compute the illuminance at each point based on the hourly climate file data (sky models) and the daylight coefficients. There is some accuracy lost by interpolating between "only" 65-ish solar positions however. These annual illuminance profiles are used to calculate the climate-based metrics DIVA reports.

I gave a talk explaining how it works at the Radiance Workshop some years ago:

J. Alstan Jakubiec- Introduction to Daysim and overview of latest developments
Slides (pdf) | Audio (mp3)

Rendering parameters that effect the point-in-time simulations will do the same with regards to climate-based simulations.




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