right, with a vray material it works better, but not perfect.
Render elements are visible in the VFB but can’t be save on the hard drive automatically (with a path in the save field).
Here is my process:
Inside render setup->render element
click “Add” to add a Vray render element like vrayAlpha…
put a path in “select element parameter”
Then when render, I can see the vray render element in the VFB but they are not save in the hard drive.
To save them, I have to do it manually from the VFB->save
So I just discover that “save separate render channels” must be on to have the render element save to Hard drive. Thanks for the info.