Simplest way to draw a line on a surface mesh?

This noob (me) wants to draw a few lines on the surface of a mesh object.
Is there a SIMPLE way to do this?

I thought of 3 ways do to so:

  1. I added edges corresponding to the lines, put the vertices of these edges in a vertex group, assigned a material to the group, but it does not show on the render, neither with the Blender internal render engine nor with the Cycles render engine, and I haven’t figured out why

  2. Using vertex paint, which seems quite overkill; I could not find a setting where the brush will add a fixed size sharp strip of color around an edge; I could only produce partial smooth coloring on the neighboring faces, kind of the opposite of what I want: a sharp fixed width coloring of the edges (I merely want to draw a line, not graffiti a surface :))
    Besides, using vertex paint with the Cycles engine seems to require using nodes yet another rather intimidating can of worm to open for a beginner

  3. Doubling the number of edges, in effect creating faces on the mesh to where I want the lines to be, which also seems overkill.

It seems strange to this noob that it is so time consuming and complex to just draw a few lines on a surface.
So what’s the right tool to use for such a simple need?

Thanks very much in advance.

are you on UV image or proc texture?

you could paint some lines on it !

if you try to render a simple line it wont show it is only one pixel wide!

happy bl

You could UV unwrap your mesh, create new image in the UV/Image editor (while all UVs are visible and that image gets assigned to them), go to texture paint mode and paint. After that you could save the image, assign a material and add a texture with the newly created image.

Another way to draw is to use the grease pencil, convert grease pencil strokes to curves, then convert that to mesh (quicker than editing curve properties) and then assign a wire material and render.

From left: grease pencil lines, curve (unedited), mesh with a wire material.

The wireframe material trick did the job. Thank you very much.