[REQ] light level / radiance

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Juju
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[REQ] light level / radiance

Post by Juju » Wed Sep 23, 2015 7:27 pm

I'm hoping this could be done without too much fuss.

Currently Indigo doesn't do light level / radiance readings / output, so this has to be done using some other software (Indigo remains rendering solution of choice).

In the present IES files have to be loaded/linked using skIndigo (or whatever other exporter you use) for rendering and again the same in the other software (eg. LightUp) for lighting level / radiance readings. Will it be possible to set these sources up on a separate layer (linking the IES files with an extension like GOSU) and have skIndigo read the IES files this way?

I suppose the other option is to have lighting level / radiance readings output from Indigo.
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Juju
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Re: [REQ] light level / radiance

Post by Juju » Thu Jan 12, 2017 11:59 pm

Big bump from the grave. Any feedback here? I was considering going to Thea, that has this already built-in (and seems to be a decent enough rendering software), but decided to wait and see what develops with Indigo.

Doing lighting analysis (radiance / illumination) is a real PITA when you need to set it up again in another software, especially when you need to do changes.
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Juju
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Re: [REQ] light level / radiance

Post by Juju » Thu Feb 02, 2017 1:04 am

Ahem *cough cough*
This is what we're talking about...
Anybody from the dev team? No interest in pursuing this at all? Some feedback would be great...
photometric_analysis1.jpg
photometric_analysis2.jpg
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OnoSendai
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Re: [REQ] light level / radiance

Post by OnoSendai » Thu Feb 02, 2017 1:05 am

Hi Juju,
THis would be cool to add, we just have a lot of stuff to do right now.
Maybe after 4.0 is done.

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Juju
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Re: [REQ] light level / radiance

Post by Juju » Thu Feb 02, 2017 1:19 am

OnoSendai wrote:Hi Juju,
THis would be cool to add, we just have a lot of stuff to do right now.
Maybe after 4.0 is done.
Hi Ono, thanks for the reply.

Understandably so, are we talking version 4.2-ish or version 5plus-ish.

I don't suppose Glare has a roadmap of sorts for Indigo?
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Jay-ko
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Re: [REQ] light level / radiance

Post by Jay-ko » Thu Feb 02, 2017 1:32 am

That would be great!
Last edited by Jay-ko on Thu Feb 02, 2017 2:55 am, edited 1 time in total.
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Oscar J
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Re: [REQ] light level / radiance

Post by Oscar J » Thu Feb 02, 2017 2:49 am

Could be integrated as a rendering pass/channel.

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Juju
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Re: [REQ] light level / radiance

Post by Juju » Thu Nov 30, 2017 5:46 pm

* bump *
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Re: [REQ] light level / radiance

Post by Juju » Sun Dec 24, 2017 8:14 am

OnoSendai wrote:
Thu Feb 02, 2017 1:05 am
Hi Juju,
THis would be cool to add, we just have a lot of stuff to do right now.
Maybe after 4.0 is done.
Imagine what my first thought was after I saw the version 4 stable release notice in my e-mail?!

Pretty please?
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Juju
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Re: [REQ] light level / radiance

Post by Juju » Fri May 18, 2018 8:30 am

*BIG BUMP*
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StompinTom
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Re: [REQ] light level / radiance

Post by StompinTom » Wed May 23, 2018 12:00 am

I'm wondering to what extent this could be done using the untonemapped EXR (linear, scene-referred) from Indigo already.

Given that we can define the reflectance of a grey surface, and a specify a light source with a specific power / wattage, wouldn't you be able to turn the linear EXR values into useful radiance values or something?

You could run it through a simple Gain adjustment (mapping the EXR to some radiance scale) and a LUT to get the color gradient.

Or am I missing something painfully obvious.. ?

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Juju
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Re: [REQ] light level / radiance

Post by Juju » Wed May 23, 2018 2:58 am

Getting a colorized image representing illumination level is only part of the requirement of a photometric report / analysis. A scale against which this is measured (accurately relevant to certain lux levels, with some kind of lux colour chart; min / max / average luminance) and a report of sorts. Hopefully some kind of picker to pinpoint / query illumination at specific position (as per picker).

If the computational part of it is easy enough to accomplish already, it would mean that this should be fairly easy to implement, for a start anyhow. (What do I know?)

Take a look at how LightUp and TheaRender approaches this. The idea is to get to the level of what DIALux / RELUX has to offer, except the artistic rendering is much better with Indigo and you don't have to redo any work (in other software) to get an accurate Photometric Analysis (indoor and / or outdoor) from your model.

Ideally I wouldn't have to go fiddle with various render options and settings and and and, just be able to choose a menu item for Photometric Analysis (or report or whatever you want to call it) and start it from there. Probably a few other minor items to input / choose, but essentially fairly easy to use at the end.

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thesquirell
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Re: [REQ] light level / radiance

Post by thesquirell » Fri May 25, 2018 2:26 am

This would be a valuable addition, very precious! GoGo!

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Re: [REQ] light level / radiance

Post by StompinTom » Fri May 25, 2018 10:42 pm

On this topic, how would one get a pixel value of 1.0 from a lightsource emitting 1 lux?
  • I've set the tonemapping to linear - though this surely is bypassed when exporting an untonemapped EXR?
  • turned off vignetting for the camera,
  • set exposure to 1 (second),
  • f-stop to 1.0,
  • the emitter is uniform, with an emittance scale of 1 lux and a diffuse color of (0,0,0).
  • I'm getting a value of about 0.718 in the EXR.
  • I have 3 light sources (planes), each 1x1 metres, each with a double emittance (1 lux, 2 lux, 4 lux). These values seem to scale roughly correctly (0.718, 1.436, 2.88).
Any ideas? Have I got my units wrong or is there some other factor that influences the amount of light the camera is receiving?

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Juju
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Re: [REQ] light level / radiance

Post by Juju » Sat May 26, 2018 12:39 am

Also take into account what reflectance the surface (-s) have, the size of the space. Keep in mind that the calculations use the centre of the light source as origin, thus using a surface of 1x1m may not be accurate.

I assume you're trying to simulate using the point method? Try doing the simulation calculation manually first, then see how the simulation compares.

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