Bump Problem

[hellyeah]

Hi guys!
I´m about to re-render an older project because of some changes. Last time I rendered it was in may this year. Now I´m getting a slightly different result. I rendered a white plastic bottle and the newly rendered one has some kind of bump.
Is it possible that I´m getting this error because of different software versions?

After trying different things I found out that the bump results from a second, older material on the object. In my opinion it shouldn´t be seen at all. In addition its behavior is really strange. It only pops up whith a strength of 1%. If I change the strength to 100% it´s getting much smoother instead of higher.
If I change the order of the to materials with the bump-mat on top of the other one the bump size even changes. (??????)

I attached a sample scene. Maybe I´m just totally confused because it´s monday morning :-)

edit:
some further infos:
Corona Version: Build timestamp: Jun 17 2019 18:34:35
Version: 4.0 (core 4)
Cinema version: R20.059 CINEMA 4D Studio

System WIN10 and MacOs 10.13.6


expected behavior:



actual behavior:



btw: rendered with corona version 3 everything is fine ;-)
Thanks,
Dominik

[TomG]

May be due to changes in how material stacking works - one thing I am puzzled about, why not just delete the bump material since it "shouldn't be seen"?

[hellyeah]

that´s obviously the solution. Just wondered if it´s an behaviour someone wants to achieve. Feels like a bug.
Is there a documentation how stacking has changed?

[TomG]

The stacking changes were for displacement specifically, but not impossible they may have had (possibly unintended) changes for bump. The info for that is on the blog release post at https://corona-renderer.com/blog/corona-renderer-4-for-cinema-4d-released/ (search for stacking :) ). I guess the big question is, when stacked, would you expect bump to do? Why would you not want the bump from a lower material to show up? How would you expect it to blend with the material on top? And indeed, how does that work with, say, the native render engine and native shaders?

Cheers!

[hellyeah]

thank you for your input. Maybe it´ll be better to give it to the bug section.
Another strange behavior is that changing the bump from 1% to 100% its getting smoother. So I think somethings wrong :-)

[burnin]

Can't take a look at the scene now. But from images I gather it's the texture Sampling. MipMap to be specific. I don't know what they did to it or if it's a bug, but from my experience it just got worse.

See what happens, if you disable it (set Tex. Sampling: from MipMap to None).

[hellyeah]

Can't take a look at the scene now. But from images I gather it's the texture Sampling. MipMap to be specific. I don't know what they did to it or if it's a bug, but from my experience it just got worse.

See what happens, if you disable it (set Tex. Sampling: from MipMap to None).

You´re totally right!