corona 8 not rendering the same reflections when changing resolution

[demec]

Hello,
I'm having a problem with corona 8 not rendering the same image when increasing the resolution. Something looks wrong with the roughness amount.
Thing is I need to send to the client the high resolution image, but corona is not delivering the same result that I show her when rendering a low resolution preview.
Not sure what's going on here. My specs are ryzen 9 5950, 128gb ram. Isn't it enough for something like this? The scene is very inexpensive, almost an empty scene, I'm using a corona 8.
Please, let me know any other information you may need. Of course all maps are available and the scene is totally the same, I'm just changing the resolution. Displacement is off.
Unfortunately I can't share the max file.

Thanks in advance!

[TomG]

In case it helps, don't forget the scene can be shared only with us and only for debugging purposes (support.chaos.com, 'submit a request' and attach the scene), doesn't have to be shared here on the forum with everyone.

If you can't share the whole scene, can you share a cut down version, e.g. replacing any objects you can't share with simple cubes, that shows the same effect? Failing that, can you share the material used on the walls at least in screengrabs? What types of maps are being used, just jpg or png or something else? Which version of Max would be interesting to know too. And also of interest, what happens in between the two resolutions, does it change gradually, or is there sudden change at some resolution?

BTW, can't see this being related to memory or system specs at all.

[maru]

I think this is the result of texture filtering.

I would suggest inspecting the wall material and checking in each texture:
- if using 3ds Max Bitmaps: blur, blur offset, filtering type
- if using Corona Bitmaps: blur and interpolation type

If you have blurring set to a very low value (like 0.01) this can easily lead to such behavior.
Even if you are using the default values (1), this can happen at all.

Generally, how it works is:
- if you render a smaller image - the textures will appear more "blurry" = more smooth, there will be more reflection visible, for example in case of fine texture used as roughness or bump
- if you render a larger image - the textures will appear more "detailed" = less smooth, there will be less reflection visible

One workaround would be to increase the blurring of textures when you are rendering in higher resolution (sadly this would have to be done one by one, or with a script).

You can also try using the Corona Converter to convert between the 3ds Max native Bitmaps and Corona Bitmaps with one click. I would expect Corona Bitmap to be more consistent here.

[demec]

thank you both, I will submit the scene to support.
All maps are already corona bitmap. Also I tried some different blur values, but I didn't see any changes at all.
It doesn't look like gradually changing, I think anything above 2k will trigger this. Maps are jpg and png, all equal or above 4k. Max is 2022.
Thanks again.