UsdPreviewSurface

Note

In order to be compliant with Pixar’s UsdPreviewSurface Specification, we have refactored the native Omniverse representation. Workflows can now include a multi-node approach to define a surface. We now support the relevant nodes from the specification.

Overview

The UsdPreviewSurface shading model aims to provide a simple and intuitive set of parameters for defining a surface appearance. It is part of the larger USD ecosystem and provides a standard way to describe surface appearances in USD files. It facilitates interoperability and asset exchange between different software tools and rendering engines, making it easier to share and collaborate on 3D scenes and assets, and as such does not require MDL.

The USD Preview Surface shading model supports various features listed below. These parameters can be defined and adjusted within a USD file, allowing for consistent material representation across different applications and renderers that support USD.

Parameters

Parameters	Description
diffuseColor	The color of the material
emissiveColor	The emissive color of the material
useSpecularWorkflow	Uses Specular workflow instead of Physical workflow
specularColor	Tint color for specular reflections
metallic	A range from 0-1 describing whether the surface is Dielectric or Conductive
	0 is Dielectric (non metal)
	1 is Conductive (metallic)
roughness	The amount of reflectivity a surface has. Range is 0-1
	0 = perfectly reflective surface
	1 = no reflectivity
clearcoat	Adjusts how “thick” the clearcoat is.
clearcoatRoughness	The amount of reflectivity a surface has. Range is 0-1
	0 = perfectly reflective surface
	1 = no reflectivity
opacity	The opacity of the surface in a range from 0-1
	0 = No Opacity or “See Through”
	1 = Fully Opaque
opacityThreshold	The opacity threshold is a clamp that cuts opacity to 0 if opacity is below the threshold amount
ior	Incidence of Refraction controls how much the light is “bent” when passing through a surface
normal	Sets the normal of the surface
displacement	Shifts the rendered surface by the displacement amount
occlusion	Artificially adds shading to the surface

UsdPreviewSurface Nodes

The material graph now allows you to author a shading graph composed of multiple nodes to represent a UsdPreviewSurface. You will need supply a simple graph for compliance with USD standards that must include a UsdPrimvarReader_float2(1) set to “st” to look up UV coordinates, that plugs into the “st” port on a UsdUVTexture(2) node which then plugs into the corresponding texture port on the UsdPreviewSurface(3) node per the following example.

Note

Older scenes containing UsdPreviewSurfaces may not display correctly. If this is the case then you will need to add a UsdPrimvar_float2(1) and UsdUVTexture(2).

Nodes

Node	Description
UsdPreviewSurface	Base Definition of UsdPreviewSurface
UsdUVTexture	Node that can be used to read UV textures, including tiled textures such as Mari UDIM’s
UsdTransform2d	Node that takes a 2d input and applies an affine transformation to it
UsdPrimvarReader_float	Node that provides the ability for shading networks to consume surface-varying data defined on geometry of type float
UsdPrimvarReader_float2	Node that provides the ability for shading networks to consume surface-varying data defined on geometry of type float 2
UsdPrimvarReader_float3	Node that provides the ability for shading networks to consume surface-varying data defined on geometry of type float 3
UsdPrimvarReader_float4	Node that provides the ability for shading networks to consume surface-varying data defined on geometry of type float 4
UsdPrimvarReader_int	Node that provides the ability for shading networks to consume surface-varying data defined on geometry of type integer
UsdPrimvarReader_normal	Node that provides the ability for shading networks to consume surface-varying data defined on geometry of vector type normal
UsdPrimvarReader_point	Node that provides the ability for shading networks to consume surface-varying data defined on geometry of type point
UsdPrimvarReader_vector	Node that provides the ability for shading networks to consume surface-varying data defined on geometry of type vector

Note

Unsupported Nodes The following nodes are provided as null objects until they are fully supported.

• UsdPrimvarReader_string

• UsdPrimvarReader_matrix