How to balance exposure and light intensity

[Sasan]

Hello everyone

I have started doing interiors, and I'm facing this problem when I use curtains to cover windows, I'm not sure how to balance HDRI, Sun , Exposure and Highlight compress. i want some light to come from the windows and lit up my interior, but when i achieve the desired lighting by increasing sun intensity which in fact is low 0.005 , the curtain material gets burned out even if highlight compress is on 999. I try increasing expsure but still it burns out the curtain material. when curtain is ok the scene is too dark. i'm trying to compare it to real life in my living room when curtrains cover up the window the space looks decently lit and a little bit of burn outs in windows. but in my render it's just way to much burn out comparing to amout of light inside? any suggestions on which takes priority exposure,light intensity?

[Bormax]

Hello Sasan

I always have about the same problem with overburned curtains. For me the best way I found is to use Corona Ray Switcher material for a curtains. Here is my example:

On the rendered results pictures marked as 1 rendered with curtain material 1 - Corona material with applied opacity and diffuse maps, translucency fraction set to 0.5.
 
Pictures marked as 2 rendered with curtain material 2 - Corona Ray Switcher material were in Direct/Reflect/Refract override slot I used material similar to material 1, but with translucency fraction set to 0.0.

How it works -  Corona material with translucency fraction set to 0.5 transmits more light and lets me fill this room with Corona's sun+sky light, and material 2 in Direct/Reflect/Refract override slot looks not burned out on renders.
In this example Sun intensity set to 0.2. On attached screenshot with material setting you can also see my Tone mapping setup - I use these settings as a starting point for interior visualization now a days.

So I believe, playing with settings of materials 1 and 2 you can find the desired result about lighting the room and direct visibility of curtains.

I would also recommend you to read this thread https://forum.corona-renderer.com/index.php?topic=28156.0 - there you can find a lot of interesting information concerning Tone mapping - I found it veeery useful.

[GeorgeK]

I would also like to add that using falloff map for your translucency fraction can assist with highlights of curtains in certain lighting scenarios, a quick example here: https://corona-renderer.com/comparer/J4V06f

The material structure was taken from Corona Material Library just add the falloff map and adjust the falloff curve.