Camera Projection - Nuke 101: Professional Compositing and Visual Effects - page 487

Notice that the building has a very strong highlight top right. The frame doesn't.
6. Select Constant1 and insert a Ramp node after it from the Draw toolbox.
The Ramp node is a simple two-point gradient producing one color that fades
along the ramp. Use this to create a highlight on the frame.
7. Move Ramp1's p1 on-screen control to top right of the frame and p0 to roughly
the center of the frame ( FIGURE 11.43 ).
Figure 11.43. Adding a highlight to the frame.