Nuke, as does most compositors, includes tools that allow you to relight scenes after they have been rendered from a 3D program. In Nuke, it is all handled by the ReLight node, a normals and a position pass.
How does it all work? VFX Creative Director at “Fire Without Smoke” Hugo Guerra shows us. Most importantly, Hugo start out by mentioning when relighting a scene should be used, and how far you can take it, without looking absurd.
Still, if you can’t re-render new lighting from the 3D source, the Nuke ReLight node will definitely come in handy, letting you add subtleties to your work.
Nuke’s ReLight node allows you to take a 2D image and relight it using 3D lights in the scene. Relight is a quick and interactive way to relight scenes in a 2D environment. It works by applying a 3D shader to a 2D image using the normal and point position passes. This way you can add multiple 3D lights via a scene node.