I was working on a scene and couldn't get the ground (not the default poser ground prop) shadow to render nicely. So I tried poser clothplane in place of the ground to see how the shadow renders and it came out exactly how I wanted it to. So after trying to figure out what could be the difference, only thing that I could find wrong with the ground prop is that the ploygon is rather large compared to the clothplane. So I increased the scale of the clothplane polygon similar to the size of the ground polygon and the shadow rendered poorly just like the ground.

Sorry if I am asking something basic here but is this right? Does shadow render differently according to the size of the polygon? I understand that shadow would cast differently, obviously, if the polygon is shaped, but if it's just a flat surface than how could it have any affect on shadow?