Shadow transitions

Hi, I hope I'm in the right category, first post ever, still trying to figure things out...
I get these polygonal shadows, happens only with Sun/Sky environment, with a HDRI light it's a smooth transition. Also recreated the lighting with a sphere primitive, renders smoothly. Figure is V9 out of the box.
What am I missing?
Sorry if this is a newbie-question, that's what I am...
Thanks, Nimrod


Shadow.jpg
299 x 484 - 55K
Comments
What subD level are you using?
I would try to increase it.