# Principled Node¶

Principled Node.

The Principled BSDF that combines multiple layers into a single easy to use node. It is based on the Disney principled model also known as the „PBR“ shader, making it compatible with other software such as Pixar’s Renderman® and Unreal Engine®. Image textures painted or baked from software like Substance Painter® may be directly linked to the corresponding parameters in this shader.

This „Uber“ shader includes multiple layers to create a wide variety of materials. The base layer is a user controlled mix between diffuse, metal, subsurface scattering and transmission. On top of that there is a specular layer, sheen layer and clearcoat layer.

Bemerkung

The emphasis on compatibility with other software means that it interprets certain input parameters differently from older Blender nodes.

## Inputs¶

Base Color
Diffuse or metal surface color.
Subsurface
Mix between diffuse and subsurface scattering.
Average scattering distance for RGB channels.
Subsurface Color
Subsurface scattering base color.
Metallic
Mix between dielectric (diffuse and specular with possible transparency) and metallic (fully specular with complex Fresnel).
Specular

Amount of dielectric specular reflection. Specifies facing (along normal) reflectivity in the most common 0 - 8% range.

Hinweis

To compute this value for a realistic material with a known index of refraction, you may use this special case of the Fresnel formula: $$specular = sqr((ior - 1)/(ior + 1)) / 0.08$$

For example:
• water: ior = 1.33, specular = 0.25
• glass: ior = 1.5, specular = 0.5
• diamond: ior = 2.417, specular = 2.15

Since materials with reflectivity above 8% do exist, the field allows values above 1.

Specular Tint

Tints the facing specular reflection using the base color, while glancing reflection remains white.

Normal dielectrics have colorless reflection, so this parameter is not technically physically correct and is provided for faking the appearance of materials with complex surface structure.

Roughness

Specifies microfacet roughness of the surface for diffuse and specular reflection.

Hinweis

When converting from the older Glossy BSDF node, use the square root of the original value.

Anisotropic
Amount of anisotropy for specular reflection.
Anisotropic Rotation

Rotates the direction of anisotropy, with 1.0 going full circle.

Hinweis

Compared to the Anisotropic BSDF node, the direction of highlight elongation is rotated by 90°. Add 0.25 to the value to correct.

Sheen
Amount of soft velvet like reflection near edges, for simulating materials such as cloth.
Sheen Tint
Mix between white and using base color for sheen reflection.
Clearcoat
Extra white specular layer on top of others. This is useful for materials like car paint and the like.
Clearcoat Roughness:
Roughness of clear coat specular.
IOR
Index of refraction for transmission.
Transmission
Mix between fully opaque surface at zero and fully glass like transmission at one.
Transmission Roughness
With GGX distribution controls roughness used for transmitted light.
Normal
Controls the normals of the base layers.
Clearcoat Normal
Controls the normals of the Clearcoat layer.
Tangent
Controls the tangent for the Anisotropic layer.

## Properties¶

Distribution

Microfacet distribution to use.

GGX
A method that is faster than Multiple-scattering GGX but is less physically accurate. Selecting it enables the Transmission Roughness input.
Multiple-scattering GGX
Takes multiple bounce (scattering) events between microfacets into account. This gives a more energy conserving results, which would otherwise be visible as excessive darkening.

BSDF