The Attribute Editor

 

Each AOV has a node associated with it. You can use the attribute editor to examine these nodes in more detail.

AOV Attributes

Light Groups

Custom AOV

Arnold Driver Advanced Output

AOV Attributes

Enabled

The AOV will only be written to disk if this attribute is checked (even if the AOV is in the active list).

Name

The name of the AOV - this will form part of the name on disk. Initially, this just takes the name from the standard names displayed in the AOV browser, but you can alter the name as needed (you should probably choose a name that enables you to tell what sort of AOV it is). Note that you can add a prefix to this name using the Prefix attribute.

Data Type

The type of data to be written in the AOV - rgba, float, vector, etc. Arnold will normally specify a default type for each AOV, so you don't have to explicitly set this.

Note that the attributes under the 'Node Behavior' tab are standard Maya attributes common to all the nodes in the scene.

Camera (Batch only)

This can be used to set a specific camera to an AOV. This only works with batch renders.

Light Groups

The contribution of multiple light sources can be written out to separate AOVs when they belong to the same light group. A light group can have multiple lights, but one light can belong to only one group. The group is defined by the AOV light group parameter of the light. 

The available light groups are listed on the right in the dialog, you can select which light groups are rendered by the selected AOVs. The group called default contains those lights which do not belong to any group (the Light Groups List is empty).

Besides the <L.'groupname'> syntax, any built-in or custom LPE can be split into multiple AOVs to output a subset of lights with a specific AOV group assigned in the light.aov parameter. For this, a postfix must be added to the LPE AOV name in options.outputs.

Light Group Example

In this example, a sphere is lit by three lights, a blue, a red and a green light. The blue and red lights have different AOV light groups defined while the green light does not belong to any group.

"default" is the beauty AOV that is lit by lights, not in any AOV light group. "RGBA_default" + "RGBA_red" + "RGBA_blue" give the total RGBA beauty pass.

A maximum of 16 different light AOVs are supported, although a given AOV can contain a bundle of any number of lights.

Global AOV

Outputs a Beauty AOV that contains those lights which do not belong to any group.

All Light Groups

Outputs one AOV per light group in the scene. When the All Light Groups checkbox is enabled then each of the light groups will be rendered. Otherwise only the selected ones will be rendered. With Batch rendering, it will output everything in the same EXR file with different channels, one for each light group.

Custom AOV

Shader

You can write the output of a shader in a via an aov_write shader. 

Light Path Expressions

You can define custom Light Path Expressions to write lighting components into separate AOVs using the following method:

  • Add a custom AOV and ensure that it is selected in the Active AOVs list.
  • You can then set the LPE in the attribute editor.

Diffuse LPE set in Custom AOV in attribute editor

To choose the type of LPE click on the  icon to the right of 'Light Path Expression'. You will see a list of available AOVs (with their associated LPE).

Other Light Path Expressions can be found here.

Arnold Driver Advanced Output

Override Path Prefix

Overrides the Maya File name prefix for the AOV.

Merge AOVs

This option saves multiple AOV layers into one multi-channel exr. It writes all enabled AOV's to one image file, naming the layers in the EXR with the name of the 'RenderPass'.

Output Mode

Choose to view the AOV in the Render View (GUI) in Batch rendering or both.

Color Management

This allows you to set a specific color space to output rendered images. By default, 8-bit images apply the View Transform through this attribute (sRGB by default), and 16/32 bit images apply the Output Transform (which is 'Raw' by default).

 

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