V-Ray Bump Normals is a render channel 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 points in depth, and Z runs up and down the screen. Bump maps are also represented in this render channel.
This render channel is similar to the Normals Render Channel, which does not include bump maps.
The Bump Normal Render Channel 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 Bump Normals, so the lighting on such objects can be adjusted by using the blue channel in compositing software.
