How to draw edges on a sphere to make parts that fit into each other I am trying to make sphere shaped designs with moving parts like spaceship doors &amp; windows for 3d printing. However, the doors/windows don't always follow the edges on the UV sphere.
Is there a way to &quot;draw&quot; edges on the surface of the sphere that I can use to cut certain shapes out of it? The best example I can think of are the classic flying saucer spaceships with the lowering door in older movies.
Below are my two objects: the sphere (orange) &amp; the shape I want to trace about the surface of the sphere to eventually cut them into two separate meshes that can fit into each other.
NOTE : I have tried using the knife projection approach and the shape does not follow the curve of the sphere. (2nd image). The third animation is the closest example I can think of for my goal.
You work with too many polygons and you should think another way. If we try something like your last picture:

Create a UV sphere, stretch it on the Z axis, keep only 1/32 that you mirror on the X and Z axis:



Cut the hole with a knife:



Extrude inwards:



Use an Array in Object Offset mode to make the mesh rotate around an empty, work on the mesh as long as necessary before applying the Mirror and Array modifiers: