Difference between Interactive and Final Render Outcomes

[Helldoor]

Hey there folks,

that's my first post here and it kinda is a bit of an urgent one, so here we go:

I'm currently working on a pretty interesting visualization project: a photographer took a photo of the rooftop of a building and my 3D model is gonna replace parts of this photo, while most of it remains as a background. To achieve that, I imported said photo as a Corona Bitmap (Environment mode: Screen), connected it to a CoronaTonemapControl, with the Exposure, Tone Mapping and LUT checkboxes unchecked and then connected it as an instance to the Direct visibility override and Reflections override.
To light up the scene I used a HDRI (Output: 1,75) and a very high Blur (2000), as the day the photo was taken on was kinda cloudy. The HDRI (imported as a Corona Bitmap) is also connected to a CoronaToneMapControl, again with all the checkboxes unchecked and finally instanced to Scene Environment > Single map slot.
(If that may be important, for the parts of the rooftop terrace I won't be changing I have a Shadow Catcher plane, with a CoronaShadowCatcher material applied, where the Backplate slot is connected to the same CoronaTonemapControl, which is also instanced in the Direct visibility and Reflections override.)

Generally it works great and I managed to Photomatch and build my geometry to very neatly fit into the photo surroundings. The Interactive Render preview looks exactly as I want my image to be. But there are some anomalies:

. Tone Mapping in the VFB kinda behaves funny: while Interactive Rendering, every value I change in the Tone Mapping (in the VFB) also applies to the background and the HDRI I use for lighting the scene, even though both have the CoronaTonemapControlTexmaps applied to them, where Exposure, Tone Mapping and LUT are unchecked. To undo that I have to go to one of said TexMaps and check, then uncheck the a random checkbox for the changes to only be applied to the 3d objects only and not to the image background and its light source...
Also, changing the Highlight compress to a higher value than 1,0 first applies to the whole image and after repeating the steps from above to make it apply only to the 3d geometry, the 3d geometry suddenly turns overexposed???

. Final Render and Interactive Render don't deliver the same results: while the image looks exactly as I want it to while Interactive Rendering, it becomes overexposed when I hit the (Final) Render button. What could the reason for that be?

Do you have any idea what the cause of all that may be?
Thank you a lot in advance!

[Helldoor]

Forgot to add some technical info, that may be useful:

it's Corona 5 (Hotfix 2) on Max 2021
Primary solver: Path Tracing
Secondary solver: UHD Cache
Adaptive light solver: checked

[maru]

. Tone Mapping in the VFB kinda behaves funny: while Interactive Rendering, every value I change in the Tone Mapping (in the VFB) also applies to the background and the HDRI I use for lighting the scene, even though both have the CoronaTonemapControlTexmaps applied to them, where Exposure, Tone Mapping and LUT are unchecked. To undo that I have to go to one of said TexMaps and check, then uncheck the a random checkbox for the changes to only be applied to the 3d objects only and not to the image background and its light source...
Also, changing the Highlight compress to a higher value than 1,0 first applies to the whole image and after repeating the steps from above to make it apply only to the 3d geometry, the 3d geometry suddenly turns overexposed???

This is expected. Tonemap Control is not "interactive". If you change some VFB post value, you need to restart IR to see the correct results.

. Final Render and Interactive Render don't deliver the same results: while the image looks exactly as I want it to while Interactive Rendering, it becomes overexposed when I hit the (Final) Render button. What could the reason for that be?

Do you have any idea what the cause of all that may be?
Thank you a lot in advance!

This is weird and definitely shouldn't be happening as IR and regular rendering are pretty much the same thing. So you are getting different overall exposure when using IR and regular render? Can you post an example of that?

[Helldoor]

This is weird and definitely shouldn't be happening as IR and regular rendering are pretty much the same thing. So you are getting different overall exposure when using IR and regular render? Can you post an example of that?

Thanks! You got it right. I also cannot understand it, as - as you said - IR and FR are one and the same, the second only having a defined output size and a render limit applied (in my case - Noise level limit)...
I'll attach the IR and FR outputs, so that you can see the difference. (the project is WIP, so the image material is confidential, please hande with care)

You'll notice the difference on the brightness of the surfaces facing the "sun" in the HDRI - they are way brighter and the differnce between the bright and shadowed sides of the buidling is a lot more unsublte. It's as if the Blurring of the HDRI didn't apply anymore, ot least not that strong...

[maru]

Can you try disabling the Adaptive light solver (Performance tab) and see if it still happens?
What kinds of lights and environment lighting are you using? (what kind of bitmap loader?)
Could you share the scene with us? The uploader is in my signature.

[Helldoor]

Sure, I'll upload the scene.
Btw, while preparing the two images for direct comparison (for my previous answer), I got the feeling, that the issue may be the HDRI. So I tried incresing the image blurring from 2000 to 6000 and I got almost the same result as in the IR. It looks as if the blurring doesn't scale along for a larger image, which sounds kinda absurd and doesn't make sense at all. But it appears to be the workaround so far.
But it still kinda looks "washed out".

As I said, I'll pack and upload the scene - I'm sure you guys will be able to find the problem, I'm too stupid to locate myself.

[Helldoor]

The scene is uploaded as an archive. Or do you need a CXR?

[maru]

The scene is uploaded as an archive. Or do you need a CXR?

Thank you, we don't need a CXR. Can you just confirm what the file name was?
We will look into this as soon as possible.

[Helldoor]

The file's called "200821_TeodorVladov_Scene4CheckUp.zip". Thank you in advance!

[maru]

I hope it's fine to post the images of your scene. Let me know if I should remove them. (I hope it's fine since you posted them already)
For me, both IR and regular render renders the same, and it's very different than your example. I am using V6 RC3 version though.

Please try:
- Disabling the Nvidia AI denoiser for IR - see: https://coronarenderer.freshdesk.com/support/solutions/articles/12000053263
- Lowering the blur value for the HDRI environment - I don't think using a value of 4500 is a good idea in any scenario. You basically end up with a solid color enviro.

[Helldoor]

Thank you very much for taking a look!

Disabling the Nvidia AI Denoiser for IR it didn`t change a thing.
I'll try using another sky - let's see if that helps eventually.
I'll keep you updated.

[romullus]

I didn't read all conversation, so i'm not sure why you need to blur HDRI, but if you do this in native bitmap loader with  blur parameter, i'd suggest to try blur offset instead. Blur is view dependent and may give you unpredictable results, especially when used with enviromental maps. On the other hand blur offset is independent from render and texture size and it's much more predictable