LuxCoreRender Forums

Hello all,

I have been looking into trying to visually represent lux measurements on a Luxcore render.

I understand from Dade, that one way to do it is with false colour setting, and trying to match each colour to the real-world values using a photometer. I think this could work, but I would need to test it at some point.

For a more reliable approach I though of working with the values for the Irradiance contour lines (see this post: viewtopic.php?f=4&t=2142). Here I found the Irradiance test.blend, but I cannot replicate the same effect.

The main difference is I am using a sun value at 1.0 gain. And there are a number of values in the camera irradiance feature, which I cannot understand mathematically, namely:

• Scale
  Range
  Steps
  Grid size

I have been playing around with these values, but since I don't fully understand them, particularly when applied to a sun I am getting something like this: https://bit.ly/2YoGN39

Would really appreciate any input on this workflow and figuring out the best setup for the Irradiance paths.

The sun is a LOOOOOT more powerful than artificial light sources so you need to increase the range of the contour plugin by a looooot.

With the following parameters:
you obtain this result:


Note: producing the above result takes quite some time due to noise. At the start, the lines are all mixed but the will clean over time.

There also a couple of stuff you should disable because they are not useful for your task (or may introduce artifacts in your results): bloom and denoiser.

You can save the plain rendering in EXR format and than check the pixel values to have an idea of the range of values.

Thanks Dade,

It does work, you are right, it just takes a lot of time.

If I change the steps from 32 to say 128, does it mean I will get more of the contour lines? I mean at a shorter interval on the image?

I am quite curious to understand which function is the one you used to obtain the scale as 179, and range 3,500,000.

JuandeLara wrote: Tue Oct 05, 2021 8:13 am If I change the steps from 32 to say 128, does it mean I will get more of the contour lines? I mean at a shorter interval on the image?

Yes.

JuandeLara wrote: Tue Oct 05, 2021 8:13 am I am quite curious to understand which function is the one you used to obtain the scale as 179, and range 3,500,000.

It is conversion factor to match Radiance results: https://github.com/LuxCoreRender/LuxCor ... es.cpp#L36

// Scale should be set to 179.0: the value of 179 lm/w is the standard luminous
// efficacy of equal energy white light that is defined and used by Radiance. It
// can be used here to produce the same output of Radiance.
//
// More information here: http://www.radiance-online.org/pipermai ... 03616.html

Great thank you Dade!