You would have to model basic mock ups of the surfaces you want shadows to be cast on and exclude these object from the colour and alpha channels. What renderer are you using?

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[Link to www.3dprevis.com]

Default settings.

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You'll have to use the matte/shadow material on your shadow surfaces then.

1: Create your scene objects and shadow surfaces and try to match the lighting to the real life lighting as much as possible. In the scene below, the teapot is the scene object and the plane and box are objects that I want the shadows to be cast on.

2: Select the 2 shadow objects and apply a matte/shadow material. You shouldn't need to change any settings.

3: Render result

4: Disregard this image, I stuffed up.

5: Result when imported into Fusion or similar compositing program. Note the lack of shadow objects, but shadows are still there.

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[Link to www.3dprevis.com]

Genius! Just what I was looking. Many thanks.

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