This page provides information on the ExtraTex rollout in the Render Elements.
The Extra Texture Render Element renders the entire scene with one texture mapped onto all objects in the scene. The texture applied to the scene can be a bitmap or a procedural texture such as Dirt or Curvature.
A common use for the ExtraTex is to use Dirt as the texture, which creates an ambient occlusion element for use in the composite. In this way, ambient occlusion can be controlled separately during the compositing process.
While you can obtain a result similar to the ExtraTex render element by applying the same texture to all objects in the scene and rendering as usual, such an approach requires additional time spent on reverting to actual materials, saving different versions of the scene, etc. The ExtraTex render element provides you with a quick and easy way to render the scene with a single texture without the extra work
UI Path: ||V-Ray Asset Editor|| > Render Settings > Render Elements > ExtraTex (when ExtraTex is added as a Render Element)
Texture – Specifies the texture to apply to the scene.
Affect Matte Objects – Specifies whether to include matte objects when generating the render element. A matte object is an object that has been assigned a Wrapper Material with the Matte option enabled.