Radiance colorpict and perforate for frit modeling

I am studying workflows within Radiance to simulate frit patterns for visual comfort assessments and need help with two Raidance commands. With the help of @mostapha, I have found that colorpict with the picture.cal function allows me to map an image onto a surface (the image acting as a frit pattern). Additionally, there is the mixfunc command with the perforate.cal function, which creates a repeating pattern across a surface - good for dot frit patterns. However, I am looking for a little more clarification on these commands Here are my questions:

  • What are the acceptable file types for picture.cal?
  • What other commands exist beside -s that can dimension the perforate.cal pattern? Is it possible to set the distance between objects separately from the object size?
  • What is the relationship between RGB value in the colorpict and picture.cal commands and the transmissivity? It appears that the RGB value that I set in my image file determines the visible transmittance. I performed a simple box study with windows mapped with solid fills at three different RGB values (black, grey, white) and found a somewhat linear relationship between transmittance and RGB value. The RGB values are black (0,0,0), grey (155,155,155), and white (255,255,255) for the image files used with the colorpict + picture.cal function.

Thanks in advance for your help and insight.

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Let’s see what Greg has to share here:

Let me see if I can help later during the week!

I have a feeling that you are conflating shadow patterns created through ETFE type films with the way frits work. Perforate.cal creates physical dots that dont really mimic the behavior of frits. Perhaps have a look at the glaze script? I think its still available online as a c-shell script.

A few addendums:

  1. Have a look at all the posts (and blog posts) by Jack de Valpine regarding Radiance. He is one of the most knowledgeable Radiance experts on this issue.
  2. I am assuming your end goal is not to create polka-dotted shadow patterns through frits (in which case perforate.cal should work). If your intention is to use frits as a means to control the amount of light allowed in through a glazing, then the glaze script would be the right choice.
  3. Finally, if you dont mind a little Python wrangling, you could probably get the script on Pyrad to work (it even has a bare-bones GUI). I have contributed to that project, but I forgot that Georg had actually implemented Glaze as well.

Hi Sarith,

Thanks for the insights. Would you mind clarifying the difference between “shadow patterns created through ETFE type films” and “physical dots” that dont mimic the behavior of frit? Why can frit not be physical dots pasted onto glass? :grin:
What qualities of the perforate.cal function do not mirror the behavior of a frit? I understand frit can be both translucent or opaque - and can be modeled as such using perforate.cal just by using a trans material like below -

void mixfunc perforation_trans
6 ExampleGlass_65tvis GenericTranslucentPanel_20 uv_hole perforate.cal -s 1.0
1 0.4

I sifted through the old Radiance listserv and didnt find anything that directly answered my question. There may be some helpful hints but I believe that I may need to improve my Radiance knowledge to decipher some of the posts.

The glaze script is fairly straight forward but limited in its application since it pulls from the LBNL Optics library, which only consists of a few (two I believe), uniformly applied frit patterns, which is good for early design but limits the ability to test custom frit patterns later in design. I also believe that the results of the Glaze script is solely transmittance and reflectance values, which prevents visual assessment of frit, right? In addition, Glaze can only model glazing systems with a single or double layer of glass - so no triple pane unfortunately.

This …

…somewhat explains this…

Perhaps I havent seen enough frits, but I thought that the idea was to limit radiation and the shadow patterns were a side effect. Of all the fritted glazings that I have seen, the frits seem to obscure/blend after a distance of 10-15 meters. (If you havent seen this already,) Taoning had done an interesting presentation during the Radiance workshop in Philly, which also contains the scripts that he was using. This might give you a few pointers: https://www.radiance-online.org/community/workshops/2015-philadelphia/presentations/day3/Radiance%20Workshop_MexiMuseum_Wang.pdf

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