A Render Var is an arbitrary output computed by the renderer. When rendering with Arnold, the primary use is to define AOVs for the viewport or rendering to file. A Render Var can be set up by creating a Render Var LOP at the stage level (TAB -> Rendering -> Render Var).

More information about Creating and Setting attributes can be found here. More information about Arnold AOVs can be found here.

Common Parameters

These properties are shared across all renderers.

Render Var Common Properties

Data Type

Sets the Data Type of the AOV. Arnold matches the native USD when possible and falls back to RGB AOVs otherwise.

Source Name

The source of the AOV. Its interpretation depends on the Source Type of the Render Var for a detailed explanation, see below.

Source Type

The type of source. Currently, RawPrimvar, and LPE are supported.

  • In the case of Raw Render Vars, the Source Name value is interpreted as the Arnold AOV name, either a built-in AOV (like P or diffuse_direct) or a user-defined one.
  • In the case of Primvar Render Vars, Arnold writes the primvar named Source Name present on Primitives to the AOV, and black if the primvar is not available.
  • In the case of LPE Render Vars, Arnold uses Source Name as a light path expression. More information about using light path expressions in Arnold can be found here.

Name

The name under which the AOV gets stored. For example, when rendering to a file, this equals to the layer name in an EXR file. This also makes it possible to render the same AOV, with different filtering settings, to different layers.

Format

Overwrites the Data Type when rendering to file.

Multi Sampled

This parameter has no effect when using Arnold. Every buffer is multi-sampled, using the anti-aliasing settings from the Render Settings LOP.

Clear Value

This parameter has no effect when using Arnold.

A ticket for supporting this in the Render Delegate can be found here.


Arnold Parameters

These properties can be found under the Arnold tab on a Render Var, and their primary use is to set up a filter for the AOV.

Filter

Sets the type of the Arnold filter used for the AOV. When Filter changes, attributes will be dynamically added and removed, as required for each Arnold filter. Setting these dynamic attributes will set the equivalent attribute on the Arnold filter.


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