So I found a way to create smooth shadow casting for circle sprites. here is a picture of the event: (But with this was using light radius could be tricky)
(Sprite has Shadow Caster behavior)
and then put a circle sprite on top of the rectangles.
I even tested it with a circle size 1800 and it is still smooth and looks good. you can even add an option so people can decide how accurate they want their shadow to be.
I think what i did do not need an explanation but if you want i can explain more.