Alpha modifier, or properties, that affect the child of the group "as a single object" I try to transfer my UI design workflow into Blender and I have one major blocker.
In UI design we overuse the ability to group object and modify/animate the properties of this group like scale/position/rotation and alpha (or opacity).
The only way I found to do this is for opacity is to make controller that control the child individually and that really not the result I need. I need to control the opacity of the group as it's a single object.
Is there a way to do that without going into complex, time consuming and not easily iterative process of a compositing phase ?
For Cycles, we can use &quot;Transparent depth&quot; and test if it is 1 or more and use it to drive the alpha value.
The disk below is a non transparent sphere behind the planes.

Less than means 1 if no transparency depth else 0.
Multiply that with your wanted alpha value and plug it to the alpha channel of the shader.

If you're using objects that have several layers (for instance replace the planes by Suzanne(s)), don't forget to tune the light path max bounces for transparency in the rendering settings (as if not, some transparent part may be rendered as solid):