Shadows on video or image

How do you create a shadow on a video background when compositing 3D models ?
In other words, creating an invisible plane that only casts shadows.

Thank you

Using Fusion's 3D system? I described a way to produce a shadow pass here:
viewtopic.php?f=22&t=58612&p=337608#p337608

If you're rendering from a 3d program, you'll need to figure out your renderer's workflow for producing a shadow pass; they're all a little different.

I used the method that I am familiar with in Hitfilm ie the shadow casting plane is set to blend mode = multiply (with software renderer) and ReplaceMaterial3D is set to shadows only.
It works BUT the shadows are 'reflections' of the material wrapped on the test cube - I have coloured shadows ?

Any ideas please ?

Thank you.

Fixed it: In Spotlight, set 'All materials to None Transmissive' - shadows now working