filtering, bump and roughness

[zaar]

Hi!

I remember seeing threads about how Corona takes shortcuts with filtering so we can how our nice and quick renderings, and that this usually isn't a problem in most images/scanarios. I just lost my perfectly tweaked highlights in my powder coating when going from testrenders to rendering 11,6K. Test rendering at that size isn't realistic, hardly even with regions.

What should I do to make sure my highlights have the same roughness/bump no matter what render size? And how bad will the penalty be?

[romullus]

You may want to install newest Corona 11 build and give it a try - there is new bump/normal map filtering modes that should help in situations like yours. https://forum.corona-renderer.com/index.php?topic=40442.msg217142#msg217142

[maru]

What should I do to make sure my highlights have the same roughness/bump no matter what render size? And how bad will the penalty be?

This is exactly what the new filtering options are designed for. As to penalty, we need to test this a bit more to get meaningful numbers. And you can help us with that. :)
Just please note that most likely there will be some changes to the way it works. So do not treat the current solution as the final one.

[Aram Avetisyan]

Hi,

For everyone interested, feel free to check this article for some theory and details on "Roughness modulation" mode:
https://support.chaos.com/hc/en-us/articles/19161682524305

Feel free to share your tests and feedback as well.

[TomG]

Also just to add, the filtering is not a "shortcut"; it is a deliberate thing done to reduce flickering and fireflies, especially in animations. Most if not all render engines do some sort of filtering, for the same reasons. Anyway, there is now an easy way to remove it using "None" (previously, lowering the Blur setting in the map to 0.01), this is where you might get flickering and fireflies in animations, but if not then you are free to use it :) And now if you do need some filtering to avoid problems, you can choose the new Roughness Modulation to see if that gives you preferred results compared to the old (still available as an option) Linear.

[pokoy]

Hi!

I remember seeing threads about how Corona takes shortcuts with filtering so we can how our nice and quick renderings, and that this usually isn't a problem in most images/scanarios. I just lost my perfectly tweaked highlights in my powder coating when going from testrenders to rendering 11,6K. Test rendering at that size isn't realistic, hardly even with regions.

What should I do to make sure my highlights have the same roughness/bump no matter what render size? And how bad will the penalty be?

Since you're going from small to big resolutions I doubt you'll see any improvement with the new filtering option. Also note that the new filtering options only work on bitmaps, not procedural maps like noise etc. If you know you're rendering big resolutions it's probably always better doing detail tests at the final resolution.

[zaar]

Thank you all for your replies!

I'm really glad to hear this is being worked on, and I was about to jump on the Corona 11 Build, but I have second thoughts now. I'm behind schedule anyway and I have zero time for unexpected results, and I might even need to use an external renderfarm so that would make using new plugins and stuff impossible.

And thanks, Pokoy, for the additional information. I'm using a plain old stupid noise map. It's nice with procedural textures for things like this so I don't have to retopo and unwrap super complex cad-objects. I'm thinking about trying tri-planar and a good normal map for the powder coat finish, but because of the shape of the most looked-at piece of this product, I think I will end up with smeary blends in critical places. Just think of a chamfered box with large radius chamers that everyone will stare straight at.

[zaar]

Bumping this bump related thread!


Had to make a update to this project and rendered it in a small size due to client request/time constraints, and things were much glossier. I'm just wondering were things stand on this now two years later. For procedural maps the only way to assure consistensy in roughness between different render sizes or object distance is to set the blur to 0.01?

Like as a rule of thumb one can say that when you are making fine procedural bump maps, lower the blur a lot, or things will behave strangely down the line? And for bitmaps, use roughness modulation?

[maru]

Do you have some examples of what you are getting? Without it, it's hard to imagine what exactly is going on.
Generally, the roughness modulation for bump maps, which is on by default, should help with things like rendering the same detailed bump map in high and low resolution.

[zaar]

No time to make isolated examples right now, sorry. But just imagine noise map set to a tiny scale in bump, to get the effect of a powder coated material that has a granularity to it when viewed close-up. When rendering in small resolutions or viewing the object from afar, the bump effect isn't visible and the material looks a lot shinier.

The roughness is set to 0,3 but because of the micro bump, it looks rougher (say 0,4) when rendering large. But the bump effect of the noise map dissapears in small scales and it looks like 0,3 with no bump.

This is a legacy project so all materials were set to linear. And I understand that the new default is roughness modulation, but that wouldn't help with procedural maps anyway?