V-Ray Bump Normals is a render element that stores the camera view as a normal map. The normals are generated using screen space  which uses the XYZ orientation of the camera view. With Screen space, the X axis runs left-right across the view, Y runs up-down, and Z points out of the screen. Bump maps are also represented in this render element.

This render element is similar to the Normals (V-Ray Normals) Render Element that does not include bump maps.

The Bump Normal Render Element is useful for adjusting lighting that comes from a particular direction. For example, faces of objects pointing toward the camera will be predominantly blue in V-Ray Bump Normals, so the lighting on such objects can be adjusted by using the blue channel in compositing software.

Common Uses

The Bump Normal Render Element is useful for changing the appearance of lighting in a scene in a composite without the need for re-rendering. In the example below a lighting workflow is used at a composite level to change the lighting in the scene. Note that it does not create any extra shadowing.  While the Bump Normal Render Element provides information about how lights will affect each surface; the Point Position element passes the spacial location of each pixel.  When used together it allows lights added in composite to react on the pixels as if they were the surface of the model.

Bump Normals Render Element

Original Beauty Composite

The resulting relit composite
(3 point lights of varying intensities and colors were used)