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# Q100370: Defining render passes using the RenderOutputDefine node

Warning: This article contains links to external websites

#### SUMMARY

This article explains how to define render passes in Katana and utilise renderer specific options.

#### MORE INFORMATION

To render your Katana project into a final image result you need to define which render passes (also known as AOV passes and LPE passes) you want to output. This can be done using the renderer specific node that defines the passes, together with the RenderOutputDefine node that configures output settings for the final image.

Render passes can range from Light Path Expressions (diffuse, specular, transmissive, subsurface layers, etc.) to more complex AOV layers (deep layers, motion vectors, scripts etc.)

How you set up render passes varies between renderers. However, in most cases you will need to use one OutputChannelDefine node prefixed with the renderer name
(e.g. PrmanOutputChannelDefine) and one RenderOutputDefine node for each render pass.

Here are the current renderer specific nodes:
Renderman = PrmanOutputChannelDefine
Arnold = ArnoldOutputChannelDefine
V-Ray = VrayOutputChannelDefine
3Delight = DlSettings

Setting up AOV & LPE passes

Each rendering system which can be used in Katana has its own unique way for setting up custom AOV and LPE Render passes.

For RenderMan and Arnold, we have an example project, which you can access through Katana. These examples will help you understand how to set up AOVs for your project.
To access them, open Katana and head to:

Help > Example Projects > Katana 205 - Other Technical Examples > Secondary Images (AOVs)

3Delight
3Delight uses a SuperTool to set up AOVs called DlSettings. This SuperTool holds 3Delight's render settings and image layers in one node, making it unique when compared to the other renderer OutputChannelDefine nodes.

RenderMan
RenderMan provide documentation on how to set up their PrmanOutputChannelDefine node options and AOV & LPE expressions at the following links:

PrmanOutputChannelDefine: RenderMan's PrmanOutputChannelDefine
RenderMan AOV expressions: RenderMan Arbitrary Output Variables
RenderMan LPE expressions: RenderMan Light Path Expressions

Arnold
Arnold offer documentation on their ArnoldOutputChannelDefine node at the following link:
Arnold Technical Guide - Arnold Shaders

Another useful community post describing how to set up an ambient occlusion pass is:
Foundry Community Forum - Setting up Arnold Ambient Occlusion pass in Katana

V-Ray
V-Ray provide a couple of examples for setting up their render passes. These can be accessed through the links below:
V-Ray Setup ExtraTex Render Elements
V- Ray Setup Material Select Render Elements

RenderOutputDefine node overview

The parameters of the RenderOutputDefine node are described in our Katana Online Help documentation, accessible under Reference Guide > 3D Nodes > RenderOutputDefine

Setting up a custom render location for your render layers

To set up a custom render location you need to select the 'locationType' parameter in the RenderOutputDefine node, and toggle it to 'f ile'. This will expose the 'renderLocation' parameter and let you define a custom file path.

If 'locationType' is set to 'local', then the render layers will be saved in your machine's temporary directory defined by `$KATANA_TMPDIR`

If you are using an asset management system then the location would be driven by the asset management implementation.

Below is an example screenshot of a RenderOutputDefine node with a custom render location defined:

Setting up render passes through a GroupStack

When you work with a large number of render passes, a great way to organise them is to keep all your RenderOutputDefine nodes compacted into a single GroupStack node.

Here is a screenshot example displaying a list of stacked passes in the GroupStack node:

Nodes can be added from the Node Graph to the GroupStack easily, by holding the Shift key while middle mouse dragging your node into the stack.

If you would like to know more about the GroupStack node's parameters and uses, please have a look at our Katana Online Help documentation under Reference Guide > Miscellaneous Nodes > GroupStack