Author Topic: Global Volume (Fog) reduces & removes Hdri Reflecions  (Read 2811 times)

2021-11-26, 17:58:48

Anthe.cr3

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Hi there

Not quite sure if my settings are incorrect, if this is a limitation to Corona, or if Light really works like this (which i don't think)

Long story short, when I add global Volume for a Distance Fog effect, the Hdri Reflections on the ground (see attachment) dissappear, but are still visible on the car though.


I tried "Single bounce only" in the Volume shader settings checked & unchecked.


There are no funky "general" render settings, Overrides or compositing tags added to any objects.


On my screenshot, the left half of IR is with the Global Volume turned on, the right half of IR is with Global Volume turned off --> see the difference on the ground reflections of the Hdri

( P.S: i could solve this by adding a huge Box object in the back of the scene and add the volume shader to it instead of a Global Volume, but i don't know how to get a gradient "density" effect -> the "edge" of where the volume starts is visible on the ground)

Any help would be appreciated!

Thanks!





2021-11-27, 11:43:22
Reply #1

Anthe.cr3

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Another thing i noticed is the Windshield and Front lights are behaving funnyily, no reflections either, too dark

2021-11-29, 20:40:51
Reply #2

Anthe.cr3

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2021-11-29, 21:59:06
Reply #3

burnin

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More info needed...
 Along your sys. specs, best is to provide an exemplary/test scene file exposing issue.

2021-11-30, 12:38:59
Reply #4

Anthe.cr3

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Hi burnin

Thanks for the reply!


Yeah, I forgot to mention that i am currently using the "Corona Renderer 8 for Cinema 4D (Daily Build 2021-11-10)"

Running a Intel i9 9900 KF
32GB Ram
EDIT: nvidia RTX2070Super
Windows 10


Example file is in the attachment ( also with the same HDRI used in the original post attachment- it's from Polyhaven.com and 100% free, so no problems with sharing it )

In my example file, global volumetrics are turned on, no reflections visible

Turn off global volumetrics in the scene environment settings -> completely different result, visible reflections

I also attached one more screenshot of that showcased here in the Example file
« Last Edit: 2021-11-30, 13:10:45 by Anthe.cr3 »

2021-11-30, 13:29:44
Reply #5

mmarcotic

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Hi,

thanks for reporting. I confirm this a bug and will report it internally (Internal ID=802619014)

Jan
Learn how to report bugs for Corona in C4D here.

2021-12-01, 11:53:58
Reply #6

Anthe.cr3

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Okay, thank you Jan!

Greetings
Andrej

2021-12-03, 10:02:15
Reply #7

mmarcotic

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Upon further inspection, it is possible that this is incorrectly set up - The volume is rather highly set-up and it makes sense that the reflective material reflects the "fog" that is present.
If you increase the IOR in the material reflection tab to imitate more mirror-like surface, the hdri becomes visible again, as expected.

Thanks,
Jan
Learn how to report bugs for Corona in C4D here.

2022-02-07, 16:32:10
Reply #8

Anthe.cr3

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Hi Jan,

It does make sense that light travelling through fog becomes "weaker" by an amount, depending on the distance of the light source and the density of the fog, and thus the reflections get weaker-

But no matter how i set both the Absorption and Scattering settings, all the reflections from materials with an IOR of ~ 1.5 and less are eaten up to the fullest. Can Changing the settings of Absorption and Scattering make that stop? Because you mentioned that my previous test file might be incorrectly set up-

I know i could make the IOR value of the Materials higher, but it would be rather tedious when working with multiple materials on for example a car, to get a fog shot, just to change it back when going back to a "fogless" environment.

Down below i attached two reference screenshots of a Car in a Studio environment, that showcases the issue side by side.

The Glass, Tires, Plastic loose pretty much all, if not all of their reflections.



Thanks!
Andrej

2022-02-07, 18:14:15
Reply #9

TomG

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Reflections would take a double hit from volumetrics, as light would be absorbed both between viewer and object doing the reflecting, but then also from the object doing the reflecting to the object being reflected. Out of curiosity, what happens if the object being reflected is moved super close (just for test purposes)?
Tom Grimes | chaos-corona.com
Product Manager | contact us

2022-02-07, 21:15:57
Reply #10

Anthe.cr3

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Okay i believe I understand-

I attached Screenshots where i placed the lights (since in this Renault studio scene the lights are the only "reflecting thing") really close to the car ( especially Front tire and Door Plastic Trim)

Both the Tire and Plastic Trim Material have IOR of 1.52

I also made a screenshot with Volumetrics and the reflectance on both materials turned off- The effect seems very similar to "volumetrics on & activated reflectance on both materials."
As if only the Diffuse channel catches the light, and no light affects the reflectance.


And one Viewport Screenshot showing the placement of the lights


Is this behaviour really to be expected?

Thanks
Andrej

2023-05-23, 18:23:28
Reply #11

Anthe.cr3

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Hello- is there any Updates to this issue?

Been a long time now since i posted this, but something is clearly wrong with how the reflections react when Volume is in play

Thanks!

2023-05-24, 08:06:20
Reply #12

Beanzvision

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Hi there,

It might be an idea to keep track of our releases. ;) This was resolved and can be found in our V10 daily build. You can test it here: https://drive.google.com/drive/folders/1cMHzUt4QXW_KvapPe6Ar1k5e0SUKE8Ei

Please check this article covering the risks of using daily builds: Daily Builds FAQ
Use daily builds at your own risk and always make backups of important projects before opening them with a daily build installed.
Bengamin Jerrems l chaos-corona.com
3D Support Specialist - Corona l contact us
Corona Uploader l Upload
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2023-05-24, 16:00:53
Reply #13

Anthe.cr3

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Hi

Oh thank you, haven't used Corona in a while as my PC setup wasn't sufficient enough to render with CPU

Will check it out!


Greetings

2023-05-25, 10:06:10
Reply #14

Beanzvision

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Hi, no problem at all. There are many new goodies waiting for you in the newer versions ;)
Bengamin Jerrems l chaos-corona.com
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