hi.
my render is via VBF and not max frame buffer.
1. How do I define region render in the view port (or there is other way) without render the all scene first?
2. after i upgrade to the new vray, I noticed that if i make render to the all scene and after then i making region render, the render witch out of the region frame is delete and become black.
how can i avoid this?
Thanks
Hi, 
1. To do a region directly in your viewport, click on the “Rendered Setup” button on the Main Toolbar (or just hit F10 on the keyboard) and then in the “Common” tab you’ll find “Area to Render”. Change it from “View” to “Region”. You’ll see a rectangle appearing in your currently active viewport (the one that has a yellow border). Here’s a Youtube video.
Note: If you have a region render in your viewport and in VFB, the region in VFB takes precedence over the one in the viewport.
2. Go to “Rendered Setup” (F10), then go to the “Settings” Tab. You’ll see a green button that says “Default”. Click it to reveal more options. Now you’ll see a setting called “Previous render”. From the list choose “Unchanged”.
Let me know if this helped.
Or this…