Hi Stu - here is a python script that may get you something - it is pretty hacky, but it may get you the curves you need, as well as some you don't - you'll need a plane for the ground plane for now, and it only casts and receives shadows on surfaces, polysurfaces and extrusions, not meshes, but these can be added.
RunPythonScript to run the script, or
-RunPythonScript "Full path to script file in double quotes" to run it. You pick the objects to cast shadows and then the targets, then set two points for the light direction.
Now, it's dumb - it casts the light forward and back along the direction vector and does not know about overlapping objects - i.e. nothing blocks the light...But it may help at least and it can be tuned up more on a rainy day.
Guaranteed somewhat tested.
ShadowCurves.py (2.1 KB)