Corona Renderer for 3ds Max > [Max] Tutorials & Guides

Specular To IOR (OSL)

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Matthew86:
Hi Dubcat! Great work as usual! Can I ask you a clarification about the use of megascans textures? I am a C4d + Corona user and I'm struggling to undesrtand if i have to use the textures with the embedded color profile or if I have to change it to linear.
Usually I use the maps in this order:


* AO (multiply) + Albedo
* Roughness (with the new phisical material of corona 7)
* Specular map: inside the IOR slot, with a value of 1.79, with a corona color correct shader to apply the LUT Specular To Ior v2
* Normal map: inside corona normal shader
All the textures with the embedded color profile. Is it correct? What is the right setup?
Thanks for the help!!


dubcat:

--- Quote from: dfcorona on 2021-02-17, 18:51:57 ---I'm also looking forward to UE 5

--- End quote ---

Me too!


--- Quote from: Jpjapers on 2021-02-23, 16:55:56 ---Ive missed these dubcat posts.

--- End quote ---

<3


--- Quote from: Matthew86 on 2021-03-02, 00:31:57 ---Can I ask you a clarification about the use of megascans textures?

--- End quote ---

Hey!

Just ask yourself, does this texture contain Color Information or Data Information.

Color Information would be Albedo/Diffuse/Translucency
Data Information would be Normal/Displacement/Roughness/Glossiness/Bump/IOR/Specular

Color Information = Load as sRGB / 2.2 Gamma
Data Information = Load as RGB / Linear / 1.0 Gamma

I've never used Cinema 4D, so I have no idea how they handle stuff.
I force gamma settings no matter what engine I use. In Unreal there is an sRGB switch per texture.

There are two kinds of normal maps. OpenGL and DirectX, the only difference is how they handle the Green channel.
In 3dsMax we have to load Megascans Normal Map as linear/1.0 gamma and then check the "Flip green (Y)" box in CoronaNormal.
I would download a material like "MOSSY STONE FLOOR" on Megascan, if I were testing a new engine. This material has indents in the stones, if these indents protrude, you should flip green.

Displacement map is another story. These maps should be 32bit float. But that is not the case with online stores.

If I scan my face, retopo my face, project all the details, export the difference as a 32bit displacement. I can load that linear map and use 1 displacement strength, and I will get correct minus/plus values, just as they were exported. Basically a 1:1 result.

If I exported the same map as 16 or 8 bit, the only difference is how jagged the edges are. I would have to input what the min/max values should be. We have to remap 0/1 to a new value. Because a 16/8 bit map can not go bellow 0 or above 1. Please just export displacement maps as 32bit. Megascans include the min/max values inside the .json file as cm.

But in the end, if you download textures from a site that has no standards, and they have done some inverse gamma on the albedo, and you load the map properly, it will look like shit. sadge

edit:
PS. When are we getting https://en.wikipedia.org/wiki/Double-slit_experiment in Corona peepoWide

romullus:

--- Quote from: dubcat on 2021-05-01, 03:30:06 ---PS. When are we getting https://en.wikipedia.org/wiki/Double-slit_experiment in Corona peepoWide

--- End quote ---

Maybe if you'd visit https://trello.com/b/EfPE4kPx/corona-tentative-road-map-3ds-max frequently enough, probability wave eventually would collapse to the version of reality where it's already implemented? :]

Basshunter:
I'm still trying to understand this IOR thing. I hope you guys can give me hand:

1) Why exactly is this IOR map needed and what is the physical phenomenon this map is trying to simulate?

2) Should we use IOR map for skin only or for all materials?

3) Is this method needed when using V-Ray too?

4) How do I get IOR maps when all I have is a diffuse texture?

dubcat:

--- Quote from: romullus on 2021-05-01, 10:39:40 ---Maybe if you'd visit https://trello.com/b/EfPE4kPx/corona-tentative-road-map-3ds-max frequently enough, probability wave eventually would collapse to the version of reality where it's already implemented? :]

--- End quote ---

;)


--- Quote from: Basshunter on 2021-05-01, 17:25:22 ---I'm still trying to understand this IOR thing. I hope you guys can give me hand:
1) Why exactly is this IOR map needed and what is the physical phenomenon this map is trying to simulate?

--- End quote ---

Specular/IOR map is there to help the engine fake depth. Because engine wise we are not there yet.


--- Quote from: Basshunter on 2021-05-01, 17:25:22 ---2) Should we use IOR map for skin only or for all materials?

--- End quote ---

Everything.


--- Quote from: Basshunter on 2021-05-01, 17:25:22 ---3) Is this method needed when using V-Ray too?
--- End quote ---

Yes. Unreal 5 too


--- Quote from: Basshunter on 2021-05-01, 17:25:22 ---4) How do I get IOR maps when all I have is a diffuse texture?

--- End quote ---

Every studio has its own way of generating specular/ior maps (Pro studios tends to use Artomatix). The most common way is to base them on a cross specular maps, and then invert the map, and do some custom adjustments until everything matches the reference. But if you only have a diffuse map. I would generate a normal map, with the best software you could get your hands on, and use the depth channel of the normal map to generate an IOR map. I believe I have a post on the forum on how to do that?


PS to Basshunter: Jag k├Žnner en bott, hon heter Anna, Anna heter hon, SKAAAAAAL.

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