SdrShaderNode {#Sdr_ShaderNode}

SdrShaderNode represents a dataflow-connectable computation, intended to be a node in a computational network. It has the following core fields.

Field	Description
identifier	Concise string including what the node does, type specialization, and versioning information
name	Concise string including what the node does, and type specialization
function	Concise string consisting of what the node does
version	SdrVersion that indicates the node's version
shadingSystem	Describes a system that usually has its own standard, language, and/or runtime
properties	Represents computational inputs and outputs (SdrShaderProperty)
definitionURI	Asset providing the definition of the node, determined during \ref Sdr_Registry_Discovery
implementationURI	Asset providing implementation of the node's computation, determined during \ref Sdr_Registry_Parse

SdrShaderNode is uniquely identified by a combination of identifier and shadingSystem. As a consequence of the assigned meanings above, this means a node can alternately be uniquely identified by name, version, and shadingSystem. Convenience API on SdrRegistry allows for identifying nodes using various combinations of these fields.

Note that in some cases, definitionURI and implementationURI may be the same.

Metadata {#Sdr_ShaderNode_Metadata}

SdrShaderNodeMetadata contains named metadata for SdrShaderNode and has support for custom user-defined metadata.

Below is a table of the most frequently used named metadata for easy reference. Descriptions below mirror the documentation on SdrShaderNodeMetadata itself. These named metadata items are <a href="https://github.com/PixarAnimationStudios/OpenUSD/blob/2f88bd53bd2690998c3d7507d24e8d213068deb1/pxr/usd/sdr/shaderNodeMetadata.h#L25-L38"> tokenized here</a>. In code to reference, for example, the "label" metadata key, use SdrNodeMetadata->Label.

Key	Description
label	UI hint for a user-friendly string representation
help	Help message for this node
domain	Defines groups for the broadest system categories, "rendering" by default
subdomain	Defines domain subsystems; e.g. "shading", "filtering", "lighting" in domain "rendering"
context	Describes usage group in a subdomain; e.g. "pattern", "surface", "bxdf" in subdomain "shading"
role	Provides finer granularity for contexts that contain many nodes
targetRenderer	Describes that a node was designed for (but not necessarily limited to) a specific renderer
collections	Provides a way to arbitrarily group nodes in ways that aren't captured by other metadata
implementationName	Implementation source's name for the shader, needed by some runtimes
openPages	Pages that should be opened/expanded by default
pagesShownIf	Per-page shownIf expressions; see SdrShaderProperty::GetShownIf
primvars	Primvars used by this node

Note that the following metadata items and core fields form a hierarchy useful for logically grouping nodes for UI display (see helper function SdrShaderNodeQueryUtils::GroupQueryResults).

• domain
• subdomain
• context
• role
• function
• name
• identifier

In general, metadata can be authored either by shader writers or parser plugin writers. Choice of when to author these items depends on the desired workflow.

Style Guidelines {#Sdr_ShaderNode_StyleGuidelines}

While SdrShaderNode does allow usages that don't match the descriptions above, adherence to these soft standards helps with consistent organization.

Identifier/Name/Function

identifier, name, and function should follow the below format with components separated by underscores.

\code identifier: <function><typeSpecialization><version> name: <function>_<typeSpecialization> function: <function> \endcode

<function> describes what the node does. <version> is either in form <major>_<minor> or <major>. <typeSpecialization> represents the type of the node and has the following recommendations.

• The type specialization representation should attempt to maximize meaning while disambiguating all nodes with the same function. This rule supersedes the below rules. Use your best judgement.
• Prefer a representation of the shader's output type.
• Use lowercase sdr type representations if possible (see \ref Sdr_ShaderProperty_Types).
• If the type is a fixed-size container, use the type representation and concatenate the fixed size e.g. "float3" or "color4".
• If the type is a container whose size is <b>not</b> fixed, use "vector" and concatenate the contained type with camel case. See example 2.
• If multiple type specifications are required to disambiguate a function, concatenate them with underscores. Prefer output types but use input types as necessary.
• If at any point a brief word or phrase can describe one or more type representations while disambiguating this shader from other shaders, consider preferring the brief. See example 3.

Field	Example 1	Example 2	Example 3
identifier	add_float_3	position_vectorFloat_1_9	convert_float4_surfaceShader_1
name	add_float	position_vectorFloat	convert_float4_surfaceShader
function	add	position	convert