PBR for tree barks and leaves

armagon

While i'm getting the hang of PBR in plastics and metals, i'm having a hard time working with them when it comes to environment modeling. Does anyone have any good tutorials or articles on the subject?

ZacD

Leaves rely on having a good SSS or translucency shader, which will depend on what engine you are working with. Bark is like any other PBR material, try to find the correct albedo value from charts and it will be very rough. 

armagon

That explains why my trees were so strange, i didn't realize i would need a separate material for the leaves. Thanks for info.

Koromo

I don´t have any tree barks right now but i have some leaves shading with translucency.




*In greyscale values so all three channels (RGB) are the same:
-For the gloss map: i use around 60,60,60 in the blade and 110,110,110 in the veins
-For the spec: i use 215 in the veins and 80 in the blade, if the leave have some damage/ dirtyness leave it that part completely or almost black of course, you don´t want specularity here.
-For the translucency/sss: Use a lighter yellowish colour/saturated version of the albedo OR change the values directly if your engine can without adding an additional texture

Obscura

This shouldn't be translucency because its not semi see through - only when its hit by the light from the back. You should rather try some subsurface shader.

The 215 spec value sounds insane for me for something dielectric. Thats close to the reflectivity value of the most of the metals. Generally, on the most of the dielectric material, your spec values should be around 2 - 10 ( ~ 4 % reflectivity). 

frmdbl

Leaves can vary quite a lot  in terms of roughness and translucency.

Also, often the backsides are more rough.

In UE4 there's a two sided shader that works quite well for foliage (at least for my purposes),
there's also a node called 'TwoSidedSign' that returs 1 for the front facing side and 0 for the back side.
It's quite useful for setting different values for the 2 sides.

Edit:
@Koromo
i think what you have there seems a bit too rough for the front side, I'd make it so that there's at least a hit of a reflection, keeping the lighting mind.

Koromo

Obscura said:

This shouldn't be translucency because its not semi see through - only when its hit by the light from the back. You should rather try some subsurface shader.

The 215 spec value sounds insane for me for something dielectric. Thats close to the reflectivity value of the most of the metals. Generally, on the most of the dielectric material, your spec values should be around 2 - 10 ( ~ 4 % reflectivity). 

My bad, i was using 0.084 in the spec value in Toolbag. You´re totally right, i was depending too much in the sliders instead of doing PBR correctly. And you´re right too with 

Mark Dygert

Koromo said:

I don't have much to add other than, trim out all of those transparent pixels. A handful of triangles is better than a ton of overdraw.

Koromo

Mark Dygert said:

I don't have much to add other than, trim out all of those transparent pixels. A handful of triangles is better than a ton of overdraw.

I know, i was doing that only for testing purposes of the translucency shader so it´s very rough in terms of alpha size vs actual polygon size ( simple plane). I´ll change that.

frmdbl said:

Leaves can vary quite a lot  in terms of roughness and translucency.

Also, often the backsides are more rough.

In UE4 there's a two sided shader that works quite well for foliage (at least for my purposes),
there's also a node called 'TwoSidedSign' that returs 1 for the front facing side and 0 for the back side.
It's quite useful for setting different values for the 2 sides.

Edit:
@Koromo
i think what you have there seems a bit too rough for the front side, I'd make it so that there's at least a hit of a reflection, keeping the lighting mind.

I was using the twosided shader 1 or 2 years ago in ue4 but now i´m more into Toolbag and well, it´s much more limited than unreal that has a bunch of nodes and blendings.