A matte object will not be directly visible in the scene; instead, the background color will be shown in its place. It will still appear normally in reflections and refractions and generate indirect illumination based on its actual material. Matte objects are useful for integrating rendered images into real footage.

Step-by-step guide

The setup involves 3 components - the environment, a dome light and the matte object itself.

  1. Create a simple scene with 2 PrimitiveCreate nodes and one CameraCreate node
  2. Name the two PrimitiveCreate nodes pc_plane and pc_sphere
  3. Merge the three nodes together
  4. Change the name of the Merge node to merge_geometry
  5. Set the name of the pc_plane node to '/root/world/geo/plane'
  6. Set the type to 'poly plane' and scale the plane
  7. Set the name of the pc_sphere node to '/root/world/geo/sphere'
  8. Set the type to 'poly sphere'
  9. Move the pc_sphere above the plane
  10. Move the camera to make sure that both the plane and the sphere are visible in the render
  11. Follow the DomeLight HOWTO to setup IBL for this scene
  12. Merge the merge_geometry and the MaterialAssign node for the dome light
  13. Change the name of this merge node to merge_all
  14. Create NetworkMaterial node and name it nm_env
  15. Add environment terminal to the nm_env node
  16. Create VrayShadingNode and name it env_settings
  17. Set nodeType to SettingsEnvironment
  18. Connect env_settings.out to the environment terminal of nm_env node
  19. Connect the nm_env node to the merge_all node
  20. Create MaterialAssign node and assign the nm_env to the CameraCreate node
  21. Connect the bitmap.out to the env_settings.bg_tex
  22. Create a VrayObjectSettings node and assign it to the pc_plane node
  23. Set the matte_properties.matte_surface parameter to Yes
  24. Set the matte_properties.alpha_contribution to -1
  25. Render

After you execute these steps you should get something that looks like the image below: