thanks
I find the reason.
the trees outside the windows can't be recognized by Octane.

Hey guys
yes I have reader the post------ Frequently Asked Questions ------
but,I followed the step,nothing changed.
a0040.jpg
the left is final render result,right is the preview image
as you see,there is big difference between then,especially the shadow detail.
Please,anyone know the reason ...

dose anyone know,if GTX 1070&1080 works for Octane in Cinema 4d?

I need to buy a new card.

thanks~~