[Radiance-general] Asking for informations

[Christopher Rush]

To further expand on the multiplier question… here’s my interpretation to be corrected if anyone understands differently…
-O 0 would give Watts of energy within the visible spectrum in the sky model, and apply the default 179 multiplier to convert to lumens in any outputs.
-O 1 would give Watts of energy across the full solar spectrum in the sky model, and typically would have to set a multiplier of 1 to keep Watts in any outputs.
-O 2 would give lumens of energy in the visible spectrum in the sky model, and you would have to set a multiplier of 1 to keep that in any outputs. I agree I’m not sure why to do this instead of the default 179 multiplier.


From: Germán Molina Larrain [mailto:germolinal at gmail.com]
Sent: Thursday, April 14, 2016 8:36 AM
To: Radiance general discussion
Subject: Re: [Radiance-general] Asking for informations

From my understanding,

  1.  -O0 will give you a Perez Sky... similar to the Gensky output, but using a diferent sky model. This model does not need to be told if the sky is overcast or clear. It will figure that out itself.
  2.  -O1 will give you the Perez Sky but with for the solar spectrum (i.e. solar radiation calculation)
  3.  -O2 is something that I wonder why is there.

If you want your output on Watts (or any energy unit), you should use a multiplier of 1. For Lighting units (lux, cd, lumens) you need a multiplier of 179.....I do not usually make pictures... but I hope the few I have done were correct.

Best.

2016-04-14 8:21 GMT-03:00 Terrance McMinn <t.mcminn at ocpms.com.au<mailto:t.mcminn at ocpms.com.au>>:
Follow up question:

Using gendaylit rather than the gensky sky generator we have additional -O options. -O 1 for W/m^2/sr solar radiation.
From the gendaylit man page:
The output can be set to either the radiance of the visible radiation, the solar radiance (full spectrum) or the luminance. -O[0|1|2] (0=output in W/m^2/sr visible radiation (default), 1=output in W/m^2/sr solar radiation, 2=output in lm/m^2/sr luminance).
Looking at the source code it appears the -O 0 option divides illuminance by 179 whilst the -O 1 and -O 2 don't. I couldn't see how the units are outputted from gensky (in relation to the 179 multiplier) to allow me to compare it to the gendaylit options.

One might assume that the -O 0 option would be set to similar units as the gensky generator.

From this confusion what multiplier should be used with the falsecolor program when using gendaylit options 0, 1 and 2 remembering that falsecolor has the default -m 179?

(I all cases I would be using the rpict -i option and looking for units in W/m^2)
Regards
Terrance McMinn
On 8/04/2016 10:27 am, Terrance McMinn wrote:

Thank you Chris.

From an irradiance image (-i) I didn't realise a multiplier of 1 in falsecolor provided units in W/m2

I accept the reservations. For this project a gross mapping over a large site with block building shapes, the results can only be construed as indicative.
Regards
Terrance McMinn
Yes, there is a -m multiplier option to falsecolor, which defaults to    -m 179    and should equate to lux or cd/m². Luminance in cd/m2 is the default label to display luminance unless you give the   -l lux     option for example for illuminance – both related to the 179 lumen/Watt multiplier.

However for Watts you can use    -m 1    in your options to falsecolor along with    -l W/m2    to change the label to display as W/m2. That is presuming your image is calculated with -i option for irradiance. I don’t think people would normally expect to see a Watts based radiance image in W/sr/m2.

This is also presuming the intent of your image takes into account all the shortcomings that Achim noted.

From: Terrance McMinn [mailto:t.mcminn at ocpms.com.au]
Sent: Thursday, April 07, 2016 9:39 AM
Can you configure falsecolor to map as w/sqm?

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