Sheen properties are primarily designed to produce subtle reflection for materials such as cloth.
In this article, we will look at definitions, different use cases, and case studies to understand the concept.
Principled BSDF is one of the most useful nodes in Blender. It is originated from the Disney principled model and is also known as the “PBR” shader because you can make PBR material by connecting PBR textures to it.
Primarily, The sheen and sheen tint are two parameters of principle BSDF which you have to consider only for making materials like fabric.
First of all, let’s see the description of sheen and sheen tint from the Physically-Based Shading at Disney Document.
1. Sheen- an additional grazing component, primarily intended for cloth. 2. sheen Tint- amount to tint sheen towards base color.
Note: Reading Disney Document will be a useful way to improve your knowledge in CG. Because it contains a lot of information about the nature of materials, practical observations and underlying concepts about every component.
Now, let’s see the nature of cloth material made using principled BSDF with different values of sheen and sheen tint.
Here, I have used a UV-sphere and a point light to demonstrate the concept. And some other settings are: Roughness-1, Light Intensity-2000W, UV-sphere color-red(#FF0000) and Background- Sky Texture.
For instance, To enhance the uniform effect, I just placed the point light behind the sphere. And here are the results:
- Sheen 0 & tint 0 – No effect.
- Sheen 1 & tint 0 – It shows Secular tint at a grazing angle and white color reflection (Fresnel like effect).
- Sheen 1 & tint 0.5 – Base color reflection started appearing around the sphere (a mix between white color and base color).
- Sheen 1 & tint 1 – Base color reflection alone.
Now, we want to know why it’s showing white color around the sphere! Is it from the light source (point light) or something else is going on?!
Let’s find out by changing light source color with- Sheen 1 and Sheen tint 0:
So the color is from the light source and now we can say:
1. Sheen - It is the amount of subtle (fresnel like) reflection near edges.
2. Sheen Tint - Mix between Color from the light sources and Base color (as reflection)
Let’s see a practical example to know more about the nature of sheen properties with different values.
Here we have two scenes, one with sheen: 0 and the other one with sheen: 10 (For demonstration purpose only).
The first image is almost flat and no reflection shows curtain swirl shape. On the other hand, the second image clearly shows the shape (reflection is slightly higher than the normal value). Also, I made one more render with Global Illumination (AO) enabled and here is the result:
Here we lost almost all the details in the render. So, if you want to use Global Illumination(AO) then the Principled BSDF shader is not a good choice for making fabric materials. In such cases, you may need to use a node setup that includes velvet shader.
Fabric material can be made either by using Principled BSDF shader or Velvet shader. When creating fabric material with Principled BSDF, consider changing sheen properties and turn off AO to get realistic result Blender.