Q100370: Defining render passes using the RenderOutputDefine node

Bradley Webster

Updated : July 14, 2021 20:37

Created : November 29, 2017 07:03

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. 

More information on setting up a render pass can also be found in our Katana Online Help. 

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:

• 3Delight = DlSettings
• Arnold = ArnoldOutputChannelDefine
• Redshift = RedshiftOutputChannelDefine
• Renderman = PrmanOutputChannelDefine
• V-Ray = VrayOutputChannelDefine

Setting up AOV & LPE passes

Each rendering system used in Katana has a unique way for setting up custom AOV and LPE Render passes.

For 3Delight and RenderMan, 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 inside one node, making it unique when compared to the other renderer OutputChannelDefine nodes.

For more information on 3Delight's DlSettings SuperTool, please find their documentation below:
3Delight DlSettings Super Tool

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

RenderMan's PrmanOutputChannelDefine
RenderMan Arbitrary Output Variables
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

Information on how to create a new render output or override the settings for an existing one can be found under the Defining and Overriding a Color Output Katana Online Help chapter. 

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 'file'. 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 organize 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.