Hi Michael.

re:
> Yes, check out the properties used in LightingOptions.htm

Thanks :)
DONE!

With this final tip I managed to modify an exixsting script that "render" the viewport into a file or into the clipboard.

Now, I'm able to generate two viewport renderings.

The first, that is the render of the current active viewport.

And the second, that is the "alpha channel" counterpart of the first render: the background if fully BLACK and all the objects are fully WHITE (using a particular lighting style)

In this way I can very very easily import both renderings into Affinity Photo and use the "alpha channel" render to cut-out the background of the rendered viewport.

Both renders are 8000x6000 or 12000x9000 pixels

Thanks for your help.