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The Render Settings window present a menu to select which Render Pass to view and edit. All the rendering attributes for the selected Render Pass are displayed right below (grouped by categories), just like they are in the Attribute Editor.
Render Settings window
Here The full functionality of Render Passes is explain in details in Managing Render Passes. Here is a description of the items in the Render Settings window for selecting and creating a Render Pass (the next page Managing Render Passes cover the topics in details):
Current Render Pass
This option menu lists all Render Pass currently in the scene. The All the attributes for the selected Render Pass are displayed right below. The selected one is also used for all renderings launched using Render Current Frame or Batch Render options of Maya’s Render menu. By default there is only one Render Pass and it is named 'renderPass1'.
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