Principled BSDF - Blender 4.1 Manual (2024)

Rendering method to simulate subsurface scattering.

Christensen-Burley:

An approximation to physically-based volume scattering.This method is less accurate than Random Walk however,in some situations this method will resolve noise faster.

Random Walk:

Cycles OnlyProvides accurate results for thin and curved objects.Random Walk uses true volumetric scattering inside the mesh,which means that it works best for closed meshes.Overlapping faces and holes in the mesh can cause problems.

Random Walk (Skin):

Cycles OnlyRandom walk method optimized for skin rendering. The radiusis automatically adjusted based on the color texture, andthe subsurface entry direction uses a mix of diffuse andspecular transmission with custom IOR. This tends to retaingreater surface detail and color and matches measured skinmore closely.

Blend between diffuse surface and subsurface scattering.Typically should be zero or one (either fully diffuse or subsurface)

Average distance that light scatters below the surface.Higher radius gives a softer appearance, as light bleeds into shadows and through the object.The scattering distance is specified separately for the RGB channels,to render materials such as skin where red light scatters deeper.The X, Y and Z values are mapped to the R, G and B values, respectively.

Scale applied to the radius.

Index of refraction used for rays that enter the subsurface component. This may be set toa different value than the global IOR to simulate different layers of skin.

Directionality of volume scattering within the subsurface medium. Zero scatters uniformlyin all directories, with higher values scattering more strongly forward.For example skin has been measured to have an anisotropy of 0.8.

Microfacet distribution to use.

GGX:

A method that is faster than Multiple-scattering GGX but is less physically accurate.

Multiscatter GGX:

Takes multiple scattering events between microfacets into account.This gives more energy conserving results,which would otherwise be visible as excessive darkening.

Adjustment to the IOR to increase or decrease intensity of the specular layer.0.5 means no adjustment, 0 removes all reflections, 1 doubles them at normal incidence.

This input is designed for conveniently texturing the IOR and amount of specularreflection.

Color tint for specular and metallic reflection.

For non-metallic tints provides artistic control over the color specular reflections at normal incidence,while grazing reflections remain white. In reality non-metallic specular reflection is fully white.

For metallic materials tints the edges to simulate complex IOR as found in materials such as gold or copper.

Amount of anisotropy for specular reflection. Higher values give elongated highlights along the tangent direction;negative values give highlights shaped perpendicular to the tangent direction.

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

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

Controls the tangent for the Anisotropic layer.

Mix between fully opaque surface at zero and fully transmissive at one.

Controls the intensity of the coat layer, both the reflection and the tinting.Typically should be zero or one for physically-based materials, but may be texturedto vary the amount of coating across the surface.

Roughness of the coat layer.

Index of refraction of the coat layer. Affects its reflectivity as well as the falloff of coat tinting.

Adds a colored tint to the coat layer by modeling absorption in the layer.Saturation increases at shallower angles, as the light travels fartherthrough the medium, depending on the IOR.

Controls the normals of the Coat layer, for example to add a smooth coating on a rough surface.

Controls in the intensity of the sheen layer.

Roughness of the sheen reflection.

The color of the sheen reflection.

Color of light emission from the surface.

Strength of the emitted light. A value of 1.0 will ensure that the objectin the image has the exact same color as the Emission Color, i.e. make it ‘shadeless’.