Hi all,
I made a small aircraft in Sketchup. I render it with Vray, using a hdri map.
However, the hdri map doesn't receive the shadows, as shown below:
When i place a face below it the shadows appear:
Now i want these shadows to appear at the grass of the hdri map. So basically i want the green face to be invisible, but it still has to receive the shadows of the aircraft. How to make that happen? 
Please note i am a beginner in sketchup and vray, like i haven't used it for years.... This is my first little project after a longgg break. 