Question How to display wapped grid on the surface of a mesh (terrain)?

Hello,
I want to display grid on the terrain which is a mesh so that the player can place gameobject on a cell of the grid. The mesh is not flat with higher and lower ground, I'm wondering how can I culculate and render this grid over any shape of mesh. Do I need to use shader? Can I do it with script only?

Please see the attached screenshot.
Any clue is appreicated.