Radiance colorpict and perforate

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For anyone familiar with the Radiance picture.cal and perforate.cal functions, I have a few 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. I would attach an image file visualizing this study but apparently I need ten points to do that...

Thanks in advance for your help and insight.

EDIT: Now that the diagram is uploaded, 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.

image description

kelsworth

asked 2018-06-25 17:27:17 -0500, updated 2018-06-26 07:51:13 -0500

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You should have enough points to upload now.

bobw (2018-06-25 22:52:37 -0500) edit

I suggest to post this question to radiance forum: https://discourse.radiance-online.org/

Mostapha Roudsari (2018-06-26 13:38:03 -0500) edit

Good point, Mo!

rpg777 (2018-06-26 13:46:14 -0500) edit

Thanks, Mostapha. I am still awaiting approval from the Radiance discourses site so I am exploring answers elsewhere.

kelsworth (2018-06-26 15:58:59 -0500) edit

Let me check that for you. I didn't get any notifications to approve new accounts on Radiance discourse.

Mostapha Roudsari (2018-06-26 18:55:52 -0500) edit

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OK this is like four questions. I can answer one straight off, so I'm going for it.

What are the acceptable file types for picture.cal?

picture.cal requires a Radiance HDR image as input. You can convert LDR image formats to Radiance with the utilities included in the Radiance distribution, such as ra_tiff. The trick is to use the -r option, to go in "reverse". e.g., you have an image your_image.tif that you want to use with picture.cal, so you convert it from tif to hdr like so:

ra_tiff -r your_image.tif your_image.hdr

Now you reference your_image.hdr in your material definition that uses picture.cal, etc.