How to block light from reaching certain objects

Hello,
I’m using a light object in Rhino. When I render, some areas that I don’t want illuminated are also receiving light.

What I would like to do is place a thin wall between the light and the objects I don’t want illuminated, so the wall blocks the light. However, I don’t want this thin wall to be visible in the render itself.

In other words, I want the wall to stop the light from going beyond a certain point, but at the same time I don’t want the wall to be visible in the final render.

I hope I explained my issue clearly. I would really appreciate any help or suggestions!


There is currently no way to do that with Rhino Render nor with Raytraced.

Thank you for your quick response.