How do I cut a semicircle into a curved surface?

Question

How can I cut a semi-circle out of a curved surface, such as this:

this object on a rifle

As you can see from the picture, the circled area is one I'm having trouble with. I can't seem to find a way to cut a hole into a curved surface without messing up the topology. Could someone help me with this?

possible duplicate of Cutting a circular hole in a hollow cylinder without distorting the cylinder — Ray Mairlot, May 31 '14 at 14:27
@Ray Mairlot, don't think its a duplicate, see the answers are quite different. — ideasman42, Jun 01 '14 at 02:25
The problem with this question is its not matching the photo (which shows gaps in a cylinder). — ideasman42, Jun 01 '14 at 02:27
@24Duckies - Can you edit your question so its not a duplicate of http://blender.stackexchange.com/questions/5856/cutting-a-circular-hole-in-a-hollow-cylinder-without-distorting-the-cylinder ? — ideasman42, Jun 01 '14 at 03:59
@ideasman42 yes, upon closer inspection of the picture I see the difference, was going by the title too much. — Ray Mairlot, Jun 01 '14 at 12:44

score 5 · Answer 1 · edited Jun 10 '20 at 12:57

Cutting it without messing up the topology (ngons, tris, unwanted distortions, etc.) will be hard.

However, for your specific case I think you might have better luck building the shape by extruding/filling.

For example:

Duplicate a cylinder:
Select some of the edges along the top/bottom of the cylinder and press W>Bridge edge loops:
Repeat for the other side(s), then add a solidify and a subserf modifier:

How do I cut a semicircle into a curved surface?

1 Answers1