Looking for a good way to make composite shapes. Say we have a classic tombstone. It's a half-circle on top and a rectangle on the bottom. I have tried doing this by either just burying a disk into a rectangle, or by cutting a disk in half then joining it to a rectangle. It stays 2 different parts, and if I join them together it still kinda sucks.
When I tried to fix the mesh manually it became abundantly clear that there had to be a better way.
Here's the sort of thing I end up with:
There are many ways to make a shape like that, but here's how I would do it.
I would start with a Cylinder with an even number of sides (I used 12). After adding the cylinder, rotate it on the Z-Axis so that the "flat" sides are square with the axis lines (for 12 sides, 15 degrees rotates it perfectly).
Rotate it again on the X or Y Axis, so it's "on its side", then scale along whatever axis to make it more like a coin (like in your image).
Delete the large faces, then make a loop cut around the middle of the side faces. Select all the bottom faces and delete them.
Select the 2 bottom edges and extrude (E) "downward" along the Z-Axis:
Press F to connect the 2 edges. Then, select the side "edge ring" with Alt + Left Click and select Face > Grid Fill from the menu at the top.
Do this on both sides. End result looks like this:
To make it more like a smooth "tombstone", add a bevel modifier and a subdivision surface modifier (in that order). Right click to shade smooth:
