Creating realistic material for glossy veneers

[Twibbz]

Hi all,
I’m an trying to create some realistic woods/veneers that have a top coat of glossy lacquer on them.
I don’t know if I am approaching this in the correct way. The gloss is uniform - so I was just upping the gloss value in the main wood material. This looks ok but this restricts me from providing gloss maps and bump maps to the veneer underneath the lacquer top coat. So I thought layered materials would maybe be the answer but I have been unable to create what I am looking for. Lacquered acrylic is transparent so this doesn’t mix well with the layered material.
So I tried duplicating the mesh and scaling it slightly over the other and applied the lacquer to that instead. But is that a silly way of doing things, it’s a lot of extra work for larger scenes.

Also Veneers typically reflect differently and uniquely (maybe inverted) depending on your grazing angles how could this be implemented
What’s the correct or best approach to this?

Could anyone provide some tips or examples to help?

Many thanks in advance

[pokoy]

You could play with anisotropy and/or falloff map to simulate viewing angle dependency. When applying lacquer to wood, it will soak in deeper in some structures, producing an alternating IOR and offseting the reflection angle based on grain direction and depth. Since there's no concept of this in Corona's shader you'll have to work around that gap. I saw a presentation once where a custom mental ray shader would do exactly that and change reflection direction based on a grain depth map. It was a similar trick but I have no recollection on any of the shader details, unfortunately. I *guess* it was using anisotropy and changing IOR based on a greyscale bitmap.

[Juraj]

Regarding your second issue, there is no sufficient solution to this right now, wood absolutely has unique anisotropic behavior that can't be replicated with generic shader (which can't even simulate much simpler multi-directional anisotrophy of fabrics, but wood is different league altogether from that).
I've seen some fantastic research into this, but nothing that materialized anywhere.

First time I hear there was MentalRay shader for this somewhere, will look into that. OSL in 2019 can't access BRDF, but maybe there is some clever trick for smart minds ?

[pokoy]

I don't think the shader was officially released anywhere, it was either a test or an internal production shader.

[pokoy]

With a little help from someone who knows, here's a link to a paper dealing with what you're probably after, and as Juraj suggested we lack the particular controls in the standard shading models to simulate this properly:
https://www.cs.cornell.edu/~srm/publications/SG05-wood.pdf

[Twibbz]

Thanks
So I guess we have to make do without that feature being implemented for the time being and work around it.
For the more general 1st section of the question however - what is a good setup with what we have available?

Thanks in advanced

[Twibbz]

Any ideas/help with the first part?

Thanks

[pokoy]

I played around a bit, a scene is attached - max 2016 + Corona v2 - but you'll need BerconMaps. I didn't want to mess around with any of the built in maps.

Have a look at this gif: http://www.mswee.net/xchange/Wood_Lacquer_Fiber_Reflection.gif
It's an IR recording with moving camera and light. Halfway through you'll see some sampling noise, that's when I enable bump in the Wood Fibers material, it'll add some shimmering to the reflection which looks better but needs longer to render. I haven't really taken care of making it high res proof so you'll have to add details.

In general the setup is:
• LayerMtl with
  + Diffuse Wood material
  + Wood Fibers material, using a map in Anisotropy Amount and Anisotropy Rotation (both at 15/100), mixed over the Diffuse Wood Mtl with a mix of Fresnel and the Wood Diffuse texture to make it appear on parts of the wood only. Play around with the mix values to change the effect. To control the spread of the effect, change reflection glossiness in this material.
  + Clearcoat material to add clearcoat reflection

I hope this will give you an idea of how this can be achieved. Of course, something simulating real life will look better, this solution may not work in all cases and look totally wrong, it's a cheat after all. Let me know if you have any questions.

[pokoy]

I now understand that when you referred to the first part of the question you were after different reflection amount of different wood fibers, not the viewing angle modulation.
Luckily, this quite easy: you take your original wood map and put it into the reflection and glossiness slots. Now both will modulate based on greyscale values from the original map. If you need more control, use a color correction node on these maps, contrast, brightness, gamma etc. Same goes for bump. It's pretty straight forward.

[Beanzvision]

Here's my quick test so far, I'll keep working at it.

[RenoJ]

Resurrecting an old thread rather than starting a new one.

I was wondering of anyone had any luck getting a realistic effect for veneers?

I've been trying to get some high gloss veneers to pop particularly the ripple variety which look amazing in real life but not having much luck.

[Juraj]

If you have really high-detailed, high resolution normal map, it will create certain level of natural anisotropy by itself.

Anisotropy is the crucial factor of wood look, it can't be simulated with reflection or gloss maps (they can help faking it though, so it's best to use everything).

[RenoJ]

Thanks Juraj. Good to know what to focus on.