Under what circumstances , will a shadow emerge in TGE1.52 ?

#1 Statics don't cast shadows, I don't believe. And DIF objects have their shadows baked into the terrain as part of the lightmap (so if you put new ones in or move them, you have to relight). Players/Vehicles cast shadows because of being ShapeBase objects. There are probably other conditions, but that's off the top of my head- you can always test it in scripts and verify all of this.