Is it possible to bake to a texture with animatable alpha gradient? Starting with a scene like:



I want to bake to a transparent image like:



In Gimp a gradient can be added to transparency channel:



Result should be an animatable alpha-gradient (with high transparency but visible ,then the objects should blend in along x-axis):



How can this be achieved in Blender?
Ideally all of this:


initially 20% transparency of objects
a gradient that allows to make the objects opaque from left to right
optinally a white border (no transparency at all).


All I get from the attached .blend is something like:



The transparency is lost after bake.
I had no success with baking, but could achieve the desired effect by rendering the image.


Set the materials alpha channel to initial transparency




Materials properties


Add a plane with an alpha gradient as texxture behing the scene


In Gimp create an image with the required dimensions
From the layer context menu select  Add Layer Mask

Use the Blend Tool to create tha gradient

Export to .PNG

Set camera to orthographic

Render and save the image.