Add a background grid

[vailly]

Hi everybody,

I need to do an animation of a product assembly and render it into Vray. That part, I'm fine.
But I need to add a blue and white grid in the background. I tought I could put a grid texture in the environment background and in the texture placement choose 2D (UV channel) but it just greyed out my backgound in the render. It works when I choose Type->Environement and Mapping->Screen but the grid is in the foreground, which is not good.

If someone can help me, it'll be very appreciated.
Thanks,
François