Relighting

Relighting is a compositing technique that is used to add extra light information not existing in the received 3D render information. This process facilitates additional creative tweaks in compositing. Though this technique can only provide light without considering shadowing information, additional procedures can provide a convincing approach to this limitation.

The Normal node

Relighting in Blender can be performed using the Normal node. The following screenshot shows the relighting workflow to add a cool light from the right screen. The following illustration uses a Hue Saturation Value node to attain the fake light color. Alternatively, any grading nodes can be used for similar effect. The technique is to use the Dot output of the Normal node as the factor input for any grade node.

The following screenshot shows relighting with a cyan color light from the top using the Normal node:

The light direction can be modified by left-clicking and dragging on the diffused sphere thumbnail...