boolean error on extruded circle

Hi everyone,
I’m very new to Blender, and trying to make some practice exercises. I’ve got very strange result of boolean operation difference, which is used in the tutorial to make doors and windows of the lighthouse ^_^. I’ve found that I had should use filled circle for extraction, but I had used non-filled. How can this (strange dint over the cube) be fixed?
Thanks in advance :slight_smile:


sculptureblend.blend (450 KB)

Add an edge loop above the doorway so you don’t get the long faces(Ctrl+R)
In the object data settings under the ‘Normals’ panel enable 'Auto Smooth (reduce the smooth angle to say 60) or add an edge split modifier so you get better smooth/hard shading

Thanks, edge loop worked :smiley:

Can I ask, why is this thing caused? I’ve reproduced it in more simple form, when the only difference is that one circle was filled when extruded, and other was not filled. Looks very strange :spin: