Reducing "noise" in rendered image

Hi all,
I am rendering an image of a room with only natural daylight as the light source. (Clear sky condition)

These are my Radiance parameters
-ab 2 -lr 8 -lw 0.1 -ad 4096 -aa 0.5 -ar 8 -dt 0 -ds 0 -as 2048
(Please correct my parameters if they are not optimal)

Just like to know from you guys how can i reduce the noise (Grainy black dots) in the image below?
I rendered it with ClimateStudio for 300 samples per pixel.

Thanks :slight_smile:

To me getting to the best rendering settings is still quite challenging, but maybe the following two things help :slight_smile: Must also say that I mainly do artificial lighting setups, not daylight. Anyway:

  1. check the following site:
    Looking at your settings, the settings for example for -aa and -ar are quite minimal.

  2. Let rad determine the settings for you as a starting point. Not sure how that would work as you work via ClimateStudio, but maybe you can run it outside of ClimateStudio, just to get the settings, then copy the settings to ClimateStudio.


Thanks for the reply!

Just to add on to what you say, as im still quite new to Radiance, i am actually not too sure how to import the model i have done in Rhino 7 and run it in the open source code version of Radiance.

Do you think the resolution affects the quality as well? I am rendering at 2,048 x 1,024. I was thinking if a lower resolution would help to reduce the “noises” in the image

ClimateStudio doesn’t use an ambient cache, so the only thing you can do is to run the image for more ‘passes’ (ray samples). You can edit the raytrace settings to turn the ambient cache back on, but you enter into classical scene-dependent settings issues that are well-defined in John M’s Ambient Crash Course.

In the future, we are looking into applying some of the AI-based denoisers. You could try pasting your output visualizations into such tools – some have a web interface.

Hi Alstan,

Appreciate your replies, how do i go about enabling the ambient cache? Is it through the Radiance parameters?

-aa 0 is now forced in ClimateStudio, and you can’t override it… so all you can do is to run more samples. Sorry for the misinformation as this was possible in older versions.

Hi Alstan,

I’m running at 300 spp but comparing it with a 500 spp, there doesnt seem to be much difference in the quality. Is there any way that i can enable the raytrace setting as what you have mentioned?

Hi Desmond,

No, unfortunately not from our UI. I suggest we move this off the Radiance forum as this is more UI-specific than Radiance-specific at this point.


Thanks Alstan,

I’ll try to contact the support email and see how it goes.

The main thing that jumps out at me from your option list is the -lw parameter, which should equal 1/ad with -aa 0, or “-lw 2.5e-4” in your case. Using -lw 0.1, you will send at most 10 rays per pixel to sample the indirect, which will be very noisy for this environment. I don’t think you really need to send 4096 rays, but certainly more than 10.


Thank you for the explaination Greg! Very insightful :slight_smile: