Hi from Greece!
The subject of shadows and their integration might be tricky (or delicate if you prefer) depending on the situation. This is why, especially in your situation with an ‘over’ lit studio shot it would be easier to soften the lighting avoiding any key lights and blending with an HDRI or backdrop with equivalent - overcast lighting - which would ‘explain’ the lack of shadows.
If you wished to add shadows to blend the two anyway you need;
i.to add an equivalent key light to the one assumed by the set (in you jpg this would be from top/back and to the right/ try
ii.to add equivalent green geometry to the shot as that shown by the virtual space so your shadows fall as and where they should (this is especially difficult in your case unless you add a real pavement and railings to the left of your and ‘ingest’ them with photogrametry and place in the right of the shot.
I have not found a detailed resource on the sequence of thought for handling shadows on live shots. If someone has found one please shoot here. Maybe we should look into this
I would separate this problem into two areas;
- The production part (lights/ cameras/ keyers)
2.The Unreal part
There are a number of ways to deal with the issue depending on what you can or cant do in the production part and what you need to do in the Unreal part.
Hope i added a little to your thinking - gotta go.
Unreal1ty Greece