The Nuke 3D Engine - Nuke 101: Professional Compositing and Visual Effects - page 384

Eventually you will need some kind of geometry or this setup won't mean much,
but there's still time.
6. Select ScanlineRender1 and press the 1 key to view it.
At the moment you don't see much in the Viewer, and you shouldn't. Although
youhaveacameraandaScanlineRendernode,youhavenothingtoshootthrough
thecamera.Youdon'tseeanythingintheresulting2Dimage.However,inthe3D
world, you should be seeing at least a camera. Nuke's Viewer functions as both a
2D and a 3D Viewer. You can easily switch between 2D and 3D viewing modes
by hovering the mouse pointer over the Viewer and pressing the Tab key. Altern-
atively,youcanchoose2Dor3D(orotherviewssuchasTopandFront)fromthe
View Selection drop-down menu at the top right of the Viewer as seen in FIGURE
9.3 .