Why does my arch not look like an arch when I subtract a solid?

[davidronn]

I've extruded a wall, and am trying to subtract an arch for the doorway. When I draft it wireframe, the arch is circular, as it should be. But when I extrude my arch, and subtract the solid from the door, it's no longer a circular arch, but a three sided arch. I've attached photos as references. 

 

Can anybody tell me what is happening? I know there's a way to make the arch circular, but can't remember what that process might be.

[Marissa Farrell]

What is your 3D Conversion Resolution set to in Preferences > 3D?

[AlanW]

@davidronnHi, just wondering why you dont use a door with an uncased opening or a wall recess? see attached.

Arch.vwx

[Jeff Prince]

2 hours ago, davidronn said:

Can anybody tell me what is happening? I know there's a way to make the arch circular, but can't remember what that process might be.

 

Your arch is circular, it's just rendering in low detail of Shaded mode.

Simply change your Shaded Options detail level to something higher like High or Very High and things will look smooth for you.