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Standard#

The standard physical material is a multipurpose physical material designed to reproduce most world materials. It is largely inspired from the open source AlSurface shader developed by Anders Langlands.

Standard Material on the sphere with default settings

Standard Material on the sphere with default settings

Tip

It is highly recommended to use the Autodesk Standard Surface material.

Diffuse#

The Diffuse attribute is dedicated to simulate diffuse surfaces as clay , fabric or paper. Diffuse supports backlighting using Diffuse Back Color and Diffuse Roughness to mimic backward scattering in materials such as plastic.

Lambertian suface (Diffuse Roughness to 0%) on the left and Diffuse Roughness to 100% to mimic plaster-like surface

Lambertian suface (Diffuse Roughness to 0%) on the left and Diffuse Roughness to 100% to mimic plaster-like surface

Backlighting#

Backlighting simulates thin translucency such as the one that occurs on a piece of paper or a leaf. When you set Diffuse Back Light Strength above 0% it automatically activates back-lighting. When back-lighting is activated illumination is evaluated on both side of the geometry.

Diffuse Back Light Strength set to 0%

Diffuse Back Light Strength set to 100%

Subsurface Scattering#

Subsurface scattering (SSS) simulates penetration of light trough translucent surfaces and the resulting scattering effect produced by the internal reflection before going out of the material.

The Physical Standard provides 3 layers of subsurface scattering allowing you to simulate easily skin-like materials.

By default SSS is disabled. To enable it use the Diffuse SSS Mix attribute which allows you to blend between a perfectly diffuse material and a completely translucent one.

Pure diffuse material

Pure SSS material. Mix set to 100%. Notice the translucency.

Attribute Description
Diffuse SSS Mix Mix between full SSS and diffuse. A value of 0 disables SSS computation.
Diffuse SSS Mode Sets the diffusion profile used to model subsurface scattering. Gaussian provides softest results. Cubic is sharper and provide more efficient approximation. Empirical is closer to real measurements.
Diffuse SSS Density Scale Global density scale of the material. This value is directly used to divide the subsurface distance of each layer.
Diffuse SSS Color 1 Color of the first layer of SSS
Diffuse SSS Distance 1 Scatter distance of the first layer. Higher values mean the light travels further through the object.
Diffuse SSS Weight 1 Weight of the first layer.
Diffuse SSS Color 2 Color of the second layer of SSS
Diffuse SSS Distance 2 Scatter distance of the second layer. Higher values mean the light travels further through the object.
Diffuse SSS Weight 2 Weight of the second layer.
Diffuse SSS Color 3 Color of the third layer of SSS
Diffuse SSS Distance 3 Scatter distance of the third layer. Higher values mean the light travels further through the object.
Diffuse SSS Weight 3 Weight of the third layer.

Note

SSS is only evaluated during direct diffuse computations. In indirect, the material is considered as pure diffuse.

Emission#

Emission Color simulates the emission or self illumination color of the material such as an incandescent material. Note that you can modify the strength of the emission by using the Emission Strength (defaulting to 0%)

Pure emissive material

Pure emissive material

Specular#

The Standard material provides for convenience two specular layers with fully configurable BRDF lobes and Fresnel. Each layer can override the underlying surface normal using Specular Normal Mode and Specular Normal Input attributes which is very handy when simulating scratches on clear-coat for example.

By default only the first layer of specular is activated providing a glossy specular close to a plastic.

GGX BRDF with default settings

GGX BRDF with default settings

BRDF Description
GGX GGX distribution results are very close to empirical data.
Ward Ward distribution is very close to Beckmann's but behave quite differently with anisotropy
Beckmann Beckmann distribution tends to provide sharper reflections when compared to GGX

Note

Using Specular Exit Color attribute you can set the exit color of the ray when there isn't enough depth to continue along the ray path.

Roughness#

The Roughness sets the roughness of the surface. The rougher surface is, the softer specular reflection. Perfect mirrors should have a roughness of 0% and perfectly rough (diffuse) surface should have a roughness of 100%.

Please note that the aspect of the specular reflection highly depends on the BRDF distribution which can be set using BRDF attribute.

The renders below have a Roughness set to 100%

Super rough surface with GGX BRDF

Super rough surface with Ward BRDF

Super rough surface with Beckmann BRDF

Fresnel#

You can control the Fresnel independently on each specular layer. The Fresnel is automatically computed according to the camera ray incidence angle over the normal and to the Specular Index of Refraction. By default, Specular Fresnel Mode is set to Dielectric which is more suited to non-conductive material such as plastic, organics, glass or water. For metallic materials the dedicated mode Metallic is also available which provides material presets using Specular Fresnel Preset.

Fresnel mode set to Dielectric and IOR varying from 1.4 to 5.6

Fresnel mode set to Dialectric and IOR varying from 1.4 to 5.6

Fresnel mode set to Metallic with Chromium, (rough) Aluminium and Gold presets

Fresnel mode set to Metallic with Chromium, (rough) Aluminium and Gold presets

Fresnel Energy Conservation#

The Standard material can compensate energy for diffuse and specular layering by taking into account microfacets normals. This results into much more photorealistic renders.

However, it is possible to disable this energy conversation (enabled by default) to go back to the previous method (for compatibility purpose) by disabling Fresnel Energy Conservation.

Fresnel Energy Conservation enable on the left sphere, disabled on the right one

Fresnel Energy Conservation enable on the left sphere, disabled on the right one

Fresnel Energy Conservation enable on the left sphere, disabled on the right one

Fresnel Energy Conservation enable on the left sphere, disabled on the right one

Anisotropy#

Anisotropy and Anisotropy Rotation allow you to simulate a microfacet model. Anisotropy control how much the specular highlight is stretched along its axis (50% produces a round highlight, 0% stretches around U axis and 100% around V axis) and Anisotropy Rotation specifies the major direction of microfacets (0% gives no direction, 50% gives 90 degrees rotation and 100% gives 180 rotation).

Anisotropy Rotation can be textured with a special texture map in which its Red and Green channels (X and Y) provide the anisotropy directions.

Anisotropy direction map

Anisotropy direction map

Textured Anisotropy Rotation

Textured Anisotropy Rotation

Note

The axis of the anisotropy is controlled by the first UV of the geometry when available. When no UV is available the anisotropy uses a local axis which doesn't guaranty continuity. For best results it is recommended to use a UV map with as few discontinuities (seams) as possible.

Transmission#

Transmission allows you to simulate refractive materials. By default, Transmission is linked to Specular 1 layer which means that it uses the Index Of Refraction (IOR), Anisotropy, Roughness and normal set to the first layer of specular. This behavior can be changed by changing the Transmission Link To attribute to Specular 2. Alternatively, you can set a specific IOR by disabling Transmission Link to Specular. This way, the Transmission has its own IOR and Roughness.

Standard Transmission Linked to Specular 1

Standard Transmission Linked to Specular 1

Using Transmittance Color allows you to color filter the color of ray the further it travels through the material. The Transmittance Density controls the scale factor of the attenuation of the ray.

The higher the value, the more the color of the ray shifts to the color defined by Transmittance Color.

Transmittance set to blue with a density of 0.5. Note the slight blue tint

Transmittance set to blue with a density of 0.5. Note the slight blue tint

Transmittance set to blue with a density of 4.0 Transmittance set to blue with a density of 4.0

Note

Using Transmission Exit Color attribute you can set the exit color of the ray when there isn't enough depth to continue along the ray path.

Tip

While you can mix Transmission and Diffuse/SSS, it is recommended to set the Diffuse/SSS weight to 0% when using transmission.