Not sure if I'm missing something. I duplicated the oak material several times so that I see a black outline which represents two doorpanels. If I view it in 3D (F4), the outlines are there, but soon as I render it as a PhotoRender, they disappears.
In the 3D Window, lines (with no thickness) are created. With PhotoRendering, no lines are made, so the panels need to be physically separated with a gap that will create a darker shadowed area.