Reflection slot of CoronaRaySwitch material affects GI

[dsolod]

Hello,

The subject and the attached image should be self-explanatory
Is there any way to avoid it?

Thanks,
Dmitry

[romullus]

Are you sure that's GI and not reflection? Did you try to disable reflection on the sphere's material (set IOR to 1,0 for physical, or reflection to 0 for legacy)?

[dsolod]

The image was showing CESSENTIAL_Indirect RE

Disabling the reflection is definitely not the right solution for me. But even with disabled reflection of sphere the CESSENTIAL_Indirect RE looks wrong. Please have the updated render with IOR=1.0 and test scene attached

[romullus]

Sorry, i didn't notice that it's indirect RE. Maybe Corona counts secondary reflection as GI, i don't know. I did similar setup as yours and find that you also need to set roughness to 0 in Corona physical material and then you should get indirect component without reflection influence, or simply use legacy material, which lets you turn off reflection completely. If losing reflection is not an option for you, then maybe consider render twice and compose the final image from render elements? In any case, it would be helpful if you could tell what are you trying to achieve, maybe there are alternative approaches.

[dsolod]

I have the living room with the heavy red colour carpet in it. Obviously, I can't have the ceiling and the walls without reflection
I don't mind to see the red colour in CESSENTIAL_Reflect RE but please not in Indirect one.

If it's not a bug, how can I overcome it keeping the reflection and not rendering twice?
Or is it a bug? Because V-Ray behaves the predicted way

[romullus]

If you have bright red carpet that you don't want to affect rest of the scene, then you can plug red material into rayswitcher's direct override slot and neutral grey material into all the other slots. Would that solve your issue?

[dsolod]

Unfortunately, I have the wall mirrors and glass cabinets reflecting the carpet.

Anyway, for now I will use the suggested solution from you with double rendering. Thank you!

But my main question, is it a bug or intended behaviour? In my opinion, Reflection slot shouldn't affect the GI, similar to VRayOverrideMtl

Hope it will be fixed

[romullus]

Sorry, i can't tell if it's a bug (i suspect it's not), you will have to wait for response of someone from the Corona team.

[maru]

Our team will look into this. I think it may be expected (something like what Romullus said: treating reflections as GI).

[dsolod]

Thank you maru!

Looking forward for fix or feasible workaround of my problem with explanation of this behaviour

Cheers

[Avi]

Hi,

As I have checked the file. The plane seems to be reflecting red color, and the sphere seems to be catching the red reflection from the plane. You can either zero the reflection in your object or make the plane not visible to reflection and refraction so that the red reflection will go away from the object.

Here is a video: https://bit.ly/3BfDsUu

[dsolod]

Hi Avi,
Thank you for your reply and the video
Similar ways were already discussed in this topic before with romullus and that was not the solution for me. So I had to render the interior twice with following post work

And that brought me to the question that I am addressing to Corona Team.
Is it the correct behaviour of the CoronaRaySwitch material?

Again, VRayOverrideMtl works as predicted without interfering the elements

Looking forward for your explanation

[Avi]

Hi,

Thank you for being so patient.

After discussing this issue with our devs, this is confirmed that reflections are considered indirect lighting GI after the ray has been through some glossy/diffuse reflections. I am afraid there is no workaround for this but feel free to let me know how this is blocking you in your project. Maybe we can find some other solutions.

[dsolod]

Hi Avi,

Thank you for your reply.

Do you consider this behaviour as a bug and should we wait for fix?

[maru]

Hi, I would not consider this a bug. It's just the way Corona works, and I don't think we can expect changes to this any time soon. That would be a huge change to the fundaments of Corona.

Can you explain why exactly this is an issue to you? Is it about composing an image out of render elements?