I know this is possible in V-Ray for 3DS Max but wonder if I can do the same in V-Ray for Sketchup.
I want V-ray to render only the shadow from some objects but not the objects them self. Is there a way to do it, I was looking at some material settings but no luck this far.
That is a feature we have not implemented yet. Until it’s added, you might want to try using the shadow VFB channel, it doesn’t do the same thing, but in some cases it can do the trick after a little compositing.
Didn’t have time to respond on my own question but I manage to do it. Maybe I did something wrong but the result is what I want. I just checked ‘Only visible in secondary’ in the material editor. Not a clue what it does but works like a charm 
more info here:
Thanks! Funny that guy also found out by just trying some things. And clear example from you concerning the reflections/refractions.