Opacity Node: Allows user to Define a node through which the objects in the group would be visible. The specified object serves as a window to see the group objects.

To better Understand the Functionality of Opacity node Follow the given example,

-Creating a Group Node and adding scene objects

-Select the Sphere tool Sphere Tool and create a sphere.

-Then select the Cube tool Cube Tool and create a cube.

-Now click the Group button Group Node button

-Press F9 from the keyboard to view the Hierarchy window. Here, you can see the objects created so far namely - Sphere 1, Cube 1, and Group 1.

-Within the Hierarchy window, drag Sphere 1 and drop it under Group 1.

-Following the same procedure, drag Cube 1 and drop it under Group 1.

-Now you can see that these nodes have been added in Group 1.

Hope this resolves your query.