Concrete ground shader question

[zrammanVW3LU]

Hello! Im trying to create a ground concrete shader similar to the attached, I have already created the base concrete texture (that has PBR diffuse, spec roughness, displacement and normal maps) that im satisfied with generally, but it's simply too clean, I just want to add a layer of dirt/grime on top of it and i'm not sure on how the best way to do it is?

I've read that I should use a aiMix where I connect both shading groups to 1 overall shader is 1 way to do it, but im not 100% certain. Any other (perhaps easier?) methods about doing this better? Perhaps should I edit the original PBR to include grime and dirty?

Much thanks!

[madsd]

You can move any Photoshop type blending action into Arnold via OSL, including custom blend modes. There are many sites that shows the code to blend 2 layers to get "screen" "lighten" and stuff of that nature, which is what you want. If you don't code, you can use one of the Arnold shader nodes that does different types of blends. Keep it on the shader side, it's genrally not desired to start to mix closures aka materials, if you can avoid it, for the sake of simplicity.

Note that you need to seed the new layer into both roughness, normals and perhaps diffuse etc. if you want a better integration it has to go to multiple slots.

You - must - blend normals on a correct formula, else it will look sub par. Arnold nodes has a blend mode called Normal, in the bottom, use this. Continue to integrate the new layer to the channels you use until you get the exact effect you are looking for.

[zrammanVW3LU]

Thanks for the reply Mads.

Firstly, im not a coder, im simply using Maya 2019 + Arnold 4 (6 core). What I've mainly done is used 2 layers, each with their own set of Diffuse, Normals, Roughness, and Im using a Displacelment node for the SG combo, which is giving me nice results, but im not achieving the grime/dirty layer as much as id like to be.

You said "Arnold nodes has a blend called Normal, in the bottom", where exactly do you mean? Because right now im using a aiMix node to blend both the textures together.

Im fairly sure I can get this right with the correct texture, its just old oil stains buried in the cracks of the ground. Finding that texture is the issue.

[lee_griggs]

Have you tried adding a grime texture to coat_roughness? Otherwise, there are the layer shaders.

[zrammanVW3LU]

Thanks Lee, I have not tried adding grime to the roughness of coat. I will try that. However, what kind of texture map should I be inputting into the coat? Is it just an image file? Also, is it coat_roughness or coat_normal?

[lee_griggs]

> what kind of texture map should I be inputting into the coat?

your dirt/grime texture.

>Also, is it coat_roughness or coat_normal?

Try both. See what works for you.

[zrammanVW3LU]

Will do. Ill give it a shot and let you know how it works out! Thanks.

[zrammanVW3LU]

Tried the coat_roughness and normal, didn't work. Maybe I did something wrong, but I ended up using an aiMixShader and a aiNoise to drive the textures. I'm satisfied with what I have. It's pretty close to the original attached photo.