Highlighting a portion of a 3D model

hi im currently trying to make a highlighter tool that’ll highlight wherever the user draws on over the 3D object. right now, i’m creating a MeshLine using the points where the mouse hovers over. the problem with this is that the “highlight” looks like it sticks out of the object.

is there a way to make the MeshLine look like it’s a flat object rather than just have it extruding out?