Is this the expected behavior??
Specular highlight vary wildly depending on the size of the render/distance from camera, seems also related to MIP mapping. It happens on both preview and real scene.
I think this one would be the same in 3ds Max. It’s just how things work.
Em, its just how things work in Corona or in real life as well? 
Thanks for reporting, sirio76!
In Corona/Max/C4D/other, anywhere where there is texture filtering involved. But of course a dev’s opinion would be more relevant here.
Not in real life 
I’m building all my shaders using physical samples of material inside a real calibrated setup and a 3D equivalent scene, also calibrated using correct exposure and light intensity. Results are mostly close to real life(below just a couple examples) but when I use a material with strong bump, results are inconsistent. Simply take several shots of a leather at different distance, the highlights is consistent no matter how you look at it, in Corona is just wrong and it’s worrisome that you do not consider this a critical issue. It needs to be investigated and fixed. Sorry for the rant but I’m investing time and resources in Corona and I want things to work properly
@maru or any other developers, have you seen that?
Wouldn’t bump to roughness solve those sampling issues?
I don’t know about this feature, can you elaborate?
Here is a reply from our dev team:
This issue is present in all renderers which perform texture filtering / mip-mapping and it needs special handling - here is a paper from Pixar which explains this well: TECHNOLOGY LIBRARIES — Pixar Animation Studios
We may, however, look into this - so stay tuned!
Also, please note: I am not a developer.
Thank a lot for looking into this, I really appreciate your support:)
Posted in ‘I need help’ but I guess it is the same bug as Sirio pointed out:
[https://forum.corona-renderer.com/ Bump Issue ](https://forum.corona-renderer.com/ Bump Issue )
Great, I’m so happy to hear that you’re considering to solve this!
I’d just like to point out that this report could potentially be about the same bug that I’m seeing here - https://forum.corona-renderer.com/ (Daily Build 2020-02-27 & v5) - Bump Map textures unreliable at different res.
Please anyone with similar issues report it to developers, the more we are the more likely it will be fixed.
Max Corona user here and I can confirm (along with others) that there’s a big issue with bump mapping being view/resolution dependant. The issue becomes more apparent when using micro fine bump maps (fine plastic pitting, fine stainless steel brushing e.t.c).
I’ve posted this before but if you want an example of rock solid bump/filtering implementation, at least as far as needed for our purposes take a look at this video:
The anistropy of the stainless steel is purely derived from the fine bump map (no dedicated anistropy slot) and being a dual user of Corona and Fstorm I can guarantee that if you try this in Corona using bump maps, it will break. You might get a semi decent result for one particular view but as soon as you increase the render resolution or change the view all hell breaks loose and you’ll have to re-tweak the material.
This is quite a large problem imo, as it impacts pretty much all common materials - wood, concrete and wall paint for example. The natural anistropy from the video example will be lost on common materials unless explicitly mapping it (and even then you won’t be able to get as fine a result unless rendering larger and downsampling).
This isn’t a knock on Corona - I still use it for 95% of commercial projects, I’m just trying to aid in key areas that could use some improvement.
+1
I can’t see how such an important feature has been neglected until now. An implementation like Fstorm would be ideal but I would be more than happy even if they simply solve the bug reported here. This is not a fancy new feature needed by a very few users, it is really a basic needs for all of us and it’s crucial to get consistent shaders.
Also immediately noticeable: nice tone mapping, color grading & natural looking light dynamics in FStorm…
I’m sure Corona devs are working on getting there.
+1 about the bump mapping. (I’m a Max user though)