weird, at first, i downloaded the file from 3d tutorial site, i rendered it, and i got a nice output like below. so, i wanna see what if i added a new cube into it and use a phong (material? or call shader??) like the cynlinder. but then, i got a total black output?? why? any idea? btw, you can download the .mb file from here. https://www.jozvex.com/tutorials/fg2.html scroll down and here https://www.jozvex.com/files/fg2/SkylightRoom.zip