How do you draw a path on a surface?

Question

What is a good way to draw a path on a surface in Blender?

Could you please define what you mean by 'path'? What is it for? What's the context? What are you trying to achieve and why? — Martynas Žiemys, Oct 21 '22 at 19:15
Just for illustration purposes, I want to show that you could walk along any of those "paths"/lines and end up in the same spot as where you started. — Steve, Oct 21 '22 at 19:20
https://blender.stackexchange.com/questions/159028/scientific-illustration-non-photorealistic-rendering-of-sparse-wireframe-with-d — Duarte Farrajota Ramos, Oct 22 '22 at 22:35

score 5 · Accepted Answer · answered Oct 21 '22 at 19:41

In Edit Mode, ⎇ Alt LMB an edge to select its loop, hit ShiftD LMB to duplicate it without moving it, and separate it into a different object by pressing P > Separate by Selection.

Do this for both loops separately, so that you end up with two loops in two different objects:

Back in object mode, select one of the loop object, hit ⇧ ShiftA > Grease Pencil > Object Line Art:

Set the color you want in the Line Art Object's material:

Repeat for the other loop object:

As you can see, the red one is only partially visible. To fix this, go in its modifier settings, Occlusion panel, enable Range and play with the End value:

How do you draw a path on a surface?

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