This is the link from Nuke's 3D environment to its 2D one. It translates 3D information within the Camera's view to 2D information.
The most important parameter in its properties is 'sample' in the 'MultiSample' tab. This improves the quality of the render, particularly its edges. Should motion blur be required, then the 'shutter' value should be increased to a value above 1 (as well as upping the sample 'value').