I have been experimenting with Honeybee & Ladybug. When analysing weather data, there are options to display the sky radiation using either the Tregenza sky with 145 patches or the Reinhart sky with 580 patches. Can you tell me how many sky patches are used in point in time and annual DGP calculations in DIVA?



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Hello Ian,

For point-in-time calculations, there is no sky patch methodology. DIVA is using either one of the CIE standard skies or the Perez sky, which are derived from continuous functions.

For the annual DGP calculations, these happen in two phases:

  1. The annual vertical illuminance is calculated using Daysim's daylight coefficient method (145 diffuse patches and ~65 direct solar positions).
  2. Images are rendered using the Perez sky, but only for the direct lighting component (ab 0).

The results of 1 and 2 are then combine for the glare analysis.



Thanks for clarifying Alstan.

Could you also confirm with reference to sky patches the methodology for the climate based daylight simulations please?



Hi Ian,

I'm not sure precisely what you are looking for, so here are some references:

A presentation on Daysim from the 2012 Radiance Workshop

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

Papers on the Daysim methodology

Dynamic daylight performance metrics for sustainable building design

Validation of dynamic RADIANCE-based daylight simulations for a tes...

The simulation of annual daylight illuminance distributions—a state...

Paper on the annual DGP calculations

Dynamic daylight glare evaluation



Thanks again Alstan,

Apologies for being a bit vague - I am just trying to get my facts straight before sharing the capabilities of the software with others. The material you have linked to is ideal and much appreciated.



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