Superimosing shadows on a background image

Support Materials and Textures
1

Is it possible to do the following:

Insert a background image. Then create an invisible stage with polygons roughtly matching the objects in the background image (ie floor, wall, etc). The objects material is black. Then when the stage objects receive shadows, the darker the shadow, it increases its alpha so it gives the impression of shadows on the background image.

How would i do this?

2

add a new material and select ‘only shadow’ in the material buttons. The alpha of the material controls the strength of the shadow. You may have to enable ‘Ztransp’ as well.