V-Ray Bump Normals is a render channel that stores the camera view as a normal map. The normals are generated using screen space (the Screen coordinate system in Houdini) 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 pass. For a diagram that illustrates how normal-style colors are generated, see the Normals (RenderChannelNormals) page.

This render element is similar to the Normals (RenderChannelNormals) Render Channel that does not include bump maps.  

The Bump Normals 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 RenderChannelBumpNormals, so the lighting on such objects can be adjusted by using the blue channel in compositing software.

The parameters for this render channel appear in the Parameters tab under the out Network and within the render elements node.

Name – The text added to the end of the rendered file, when saved as a separate file (e.g. myrender.Bump_Normals.vrimg).

Filtering – Applies the image filter to this channel. Image filter settings are in the AA sub-tab of the Sampler tab of the V-Ray Renderer node.

Deep Output – Specifies whether to include this render element in deep images.

The Bump Normals 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, 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 Normals Render Element provides information about how lights affect each surface; the Point Position element passes the spatial location of each pixel. When used together with the Bump Normals, it allows lights added in composite to react on the pixels as if they were the surface of the model.

See the render before and after compositing:

The Point Position pass