Juraj, finally took time to plunge a bit deeper in the paper you linked here and damn yeah! That’s really cool!
I wanted to bump, no pun intended, this thread and see if this will ever be possible in a render engine like Corona.
Is it even possible with Vray CPU or GPU?
What I’m talking about is to have a bump map to create brushed effects like in real life, the way Fstorm does it.
To create a brushed metal material, even with extreme close ups, is absolutely possible with Corona (and any modern render engine I believe). It just takes artistic control and depends on how “deep” you want to go. Simple answer will be to use texture with extreme detail, and turn off the texture filtering, so all the detail is taken into account as much as possible (0.01 filter value for Corona). But this can cause heavy flickering of the surface in case of animations. You just have to try it once and see how it “feels”. This is the reason textures are filtered by default to be safe.
I know most Corona users do stills, so you are absolutely fine to just disable filtering for textures if you want (even for all of them).
The technical part here is mostly about texture filtering, which different engines do differently or just have different control over it, in connection with the host app as well.
This has actually been to some degree covered by the new “Roughness modulation” filtering mode for CoronaPhysicalMtl - if you use extremely detailed texture for bump, it will turn out to be anisotrophy (how it works in real life). “Roughness modulation” will understand how much of the texture as bump/normal (much calculation) should be considered, and how much of it can be treated as roughness (less complex calculation), depending on the distance from camera (think of it as condensing 1000 pixels of texture into 10 pixels in render resolution). But as it takes much effort and very detailed textures, that is why renders engine have separate, more convenient control for it, to get perceptually the same effect.
I don’t think that the detail is lost in Corona.
Even if the material setup is virtually the same, render engine may have different calculation algorithms.
I would say this is simply about artistic control - getting the look you want in any render engine.
Since you guys make videos a lot, I’d be interested to see a video dedicated specifically to creating realistic clean metallic surfaces. Not cylinders but flat surfaces. Thanks.
Edit: Specifically how to remove this clear reflection without using roughness. see attached.
EDIT 2: And without using fake anisotrophy
Yeah that area is not looking good, same for the harsh reflection/highlight cutoff on the right box. What would be needed to get rid of these?
At least similar fireflies are there in Fstorm too, these would be my main concern in both renderers, wonder if they’d clean up without clamping highlights.
To be fair with Fstorm I only rendered that for 1000 Fstorm passes (not much), while I rendered the corona version for 250 Corona passes (should be enough).
I’m pretty sure Fstorm would eventually clear the fireflies but I don’t think corona could.