A single Dome light, Everything turned off in Details, but still producing internal reflections... A BUG?

[change-refuse]

Hello.

Metallic material, highly reflective. Hollow object or concave with internal self reflections... camera looking in. During testing I turned EVERYTHING off in Details but the internal reflections persist!?!?!

Am I missing something or could this be a bug?

InternalReflectionsTester.c4d

Thanks!!

[Dr. Sassi]

Hi change-refuse,

Thank you very much for the file.

Please go to the Advanced Tab of the Gold Material.

This is an option that allows to produce of artificial reflections when the amount of rays is reached.

The setting is called End Color, and if set to Environment instead of the default Diffuse, you get an artificial reflection, obviously inside the Torus Segment. That fake reflection makes no sense here, to begin with, but a black path of the end of rays doesn't look good either. I get that.
https://help.maxon.net/c4d/2025/en-us/Default.htm#html/COM_REDSHIFT3D_REDSHIFT4C4D_NODES_CORE_STANDARDMATERIAL-COM_REDSHIFT3D_REDSHIFT4C4D_NODES_CORE_STANDARDMATERIAL_GROUP_13.html#COM_REDSHIFT3D_REDSHIFT4C4D_NODES_CORE_STANDARDMATERIAL_REFL_ENDMODE

If you need that and have a completely dark scene at one point, you need to work with the Light Intensity if the End Color settings can't be changed.

If that feels not OK to you, please check with Tech Support.
https://www.maxon.net/en/support-center

All the best

[change-refuse]

WOW. Never looked in the Advanced tab of the Standard Material Node. Now that adjusting the reflection of the Dome Light is working as expected, it's giving me the same result as adjusting the Intensity. ‍ My thought was that the internal reflections were not behaving correctly as they appear much brighter than the external reflections.

THNK YOU!!! for your help and speedy response!

Can you explain why the internal reflections appear more brighter? or more intense?

[Dr. Sassi]

Thanks for the reply, change-refuse,

One reflection is light-based, and the other one is Image-based, while the image-based (environment) kicks in when it would be otherwise black.

Here is how to explore it. Set up an ACEScg 32-bit float image in Photoshop. Create a portion in 0.17, another 0.5, then 1.0, and the last patch in 1.75 (here, each time, all three channels are the same (RGB), save as Open EXR, load it into the Dome light, and set it to ACESCG. Then, place a sphere above your Torus "slice" with the same material.

Measure the Values with the PIXEL options in the RS Render View. I can't see here a lot of differences.

For quality control, I would avoid any 3rd party HDRI, especially Radiance (".hdr"). At the same time, some OpenEXR hdri holds just Radiance material, which will not help to make a bad source better.

The Test pattern that I described above will give you certainty.

Cheers