I was wondering how noise "adds up" from the different light passes into the main pass.
Lets imagine the following: A simple interior scene, a living room if you will, with only 1 window.
There are 2 light sources. One is an HDRI environment-light coming in from the outside through the window.
The other is a big light plane under the ceiling.
Lets assume the HDRI light pass is really noisy (because the window is really small).
But the light pass from the light-plane is perfectly clean and noise free. Now, my understanding is that the main pass simply adds all the passes together. Does this mean the noise from all passes are also added? What I mean is will the noise from the HDRI be visible in the main pass even though the other light cleans the scene perfectly in its light pass?