Corona correct Gamma settigns

[sumeetgupta]

Hi all

I am a vray user and planning to shift to Corona. However whenever i render my scene in Corona, I get very washed out image. Probably due to incorrect gamma settings ?
When i save the image, it looks much better. My Gamma settings -



When i render the scene, i get result like this -



When i save the image to hard disk, it looks like this(which i think is correct result). My final output and render settings-



Any suggestions are welcome. Thanks.

[maru]

In Max's preferences set output gamma to 2.2 (set 2.2 everywhere). Don't touch Corona's internal gamma settings. When saving a .jpg check "use system settings", when saving .exr, .hdr or other 32-bit file, check "override gamma" and type 1.0.

Correct me if I'm wrong.

[sumeetgupta]

In Max's preferences set output gamma to 2.2 (set 2.2 everywhere). Don't touch Corona's internal gamma settings. When saving a .jpg check "use system settings", when saving .exr, .hdr or other 32-bit file, check "override gamma" and type 1.0.

Correct me if I'm wrong.

I did set output gamma to 2.2. I still get very washed out render in Corona VFB. Every time i need to check "override gamma" to 1.0 while saving an image. Desperately need a fix.

[Ondra]

this is 3dsmax thing and it was fixed in 2014

[Ludvik Koutny]

If you have not touched gamma in corona's render settings, then what you are seeing in VFB is CORRECT, and what you are saving is WRONG!

If you are not saving to EXR files, then in your 3ds Max gamma settings, set output gamma to 2.2. That will ensure JPG, TIF, PNG, BMP and such formats are saved with correct gamma.

The reason your image is washed out is probably due to the fact you use unrealistically bright superwhite materials (above RGB 220).

Corona renders very large ray depth by default, so rays do not get terminated early, and bounce light around a lot. Superbright materials then reflect almost 100% of incoming light and result in lack of contact shadows. Superbright materials also make rendering extremely slow.

What Keymaster said is true, but most probably unrelated to this case, as he did not bother to read your post thoroughly ;)

Also, if you are opening HDRI images, for your environment for example, make sure to manually override input gamma for all HDRI files to 1.0 in open bitmap dialog. Input Gamma set to 2.2 will work correctly only for non-HDR formats, such as JPG, TIF, PNG, BMP etc...

[sumeetgupta]

If you have not touched gamma in corona's render settings, then what you are seeing in VFB is CORRECT, and what you are saving is WRONG!

If you are not saving to EXR files, then in your 3ds Max gamma settings, set output gamma to 2.2. That will ensure JPG, TIF, PNG, BMP and such formats are saved with correct gamma.

The reason your image is washed out is probably due to the fact you use unrealistically bright superwhite materials (above RGB 220).

Corona renders very large ray depth by default, so rays do not get terminated early, and bounce light around a lot. Superbright materials then reflect almost 100% of incoming light and result in lack of contact shadows. Superbright materials also make rendering extremely slow.

What Keymaster said is true, but most probably unrelated to this case, as he did not bother to read your post thoroughly ;)

Also, if you are opening HDRI images, for your environment for example, make sure to manually override input gamma for all HDRI files to 1.0 in open bitmap dialog. Input Gamma set to 2.2 will work correctly only for non-HDR formats, such as JPG, TIF, PNG, BMP etc...

This answers my question. I did use over bright materials in my scene, hence the washed output. I did a test with Corona default grey material under "Override material" rollout and it was rendering just fine.
Where are Corona gamma settings? I couldn't find it anywhere.
Thanks a lot !

[sumeetgupta]

Sorry to bombard you with questions, So, technically we cant use values above 220 in Corona(Even if we want to render white walls for eg, we need to use slight grey material ?)  and what about textures ? What if i have to render white marble in my scene, every time i need to tone down my texture in Photoshop ? And lastly, how do i know if my texture is below 220 value in RGB ?

RGB in color selector under 3DS MAX is determined with "Value" parameter, correct ?

[maru]

If your bitmap has some very bright spots and you are using it in diffuse slot, you can lower the "diffuse level" value to 0,7 - 0,6 - 0,5 depending on what you want. In reality materials are hardly ever so bright. See:
https://forum.corona-renderer.com/index.php/topic,2359.msg17366.html#msg17366
https://forum.corona-renderer.com/index.php/topic,1012.msg13575.html#msg13575
https://corona-renderer.com/wiki/performance_debugging

You can also use albedo render element to determine if some parts of your scene are too bright.

[Ludvik Koutny]

Sorry to bombard you with questions, So, technically we cant use values above 220 in Corona(Even if we want to render white walls for eg, we need to use slight grey material ?)  and what about textures ? What if i have to render white marble in my scene, every time i need to tone down my texture in Photoshop ? And lastly, how do i know if my texture is below 220 value in RGB ?

RGB in color selector under 3DS MAX is determined with "Value" parameter, correct ?

Yes, and to make sure textures are not overbright, you can set diffuse level in material to around 0.85 to make sure your diffuse won't become overly bright.

Also for reference. RGB 220 is usually a sheet of white paper. RGB 230 is fresh alpine snow. So not many things are brighter than that. For white walls, i usually use RGB 190-200.

[sumeetgupta]

Thanks for your reply, I will try your suggestions and post my results soon.