The Material Select Render Element isolates and renders only objects in the scene to which a specific material is applied. All objects in the scene with the specified material will render normally with proper lighting, reflections and refractions, and all other objects will simply render black.

While you may only have one material at a time specified in a single Material Select element, you may have as many Material Select elements as needed in your scene.

Step-by-step guide

  1. Create a PrimitiveCreate node and name it pc_plane

  2. Create a NetworkMaterial node

  3. Merge the pc_plane and NetworkMaterial nodes

  4. Connect a MaterialAssign node to the Merge node

  5. Assign the NetworkMaterial node to the pc_plane

  6. Add a V-Ray surface terminal to the NetworkMaterial node

  7. Create two VrayShadingNode nodes and name them mtl_plane and mtl_select_plane

  8. Set the nodeType of mtl_plane to VRayMtl

  9. Adjust the parameters to make the material red and reflective for example

  10. Set the nodeType of mtl_select_plane to VRayMtlSelect

  11. Connect mtl_plane.out to mtl_select_plane.material

  12. Create a CameraCreate node

  13. Merge the CameraCreate and the MaterialAssign node

  14. Create a GafferThree node, add a light to it (a LightDome was used in the example below) and connect it to the Merge node

  15. Create a VrayOutputChannelDefine node and name it vocd_mtl_select_plane, connect it to the GafferThree node

  16. Set its name parameter to pass_select_plane. Then set  the type parameter to material_select.

  17. Create a RenderOutputDefine node and name it rod_mtl_select_plane

  18. Connect it to the vocd_mtl_select_plane node

  19. Set the outputName parameter to mtl_select_plane

  20. Set the parameter to pass_select_plane

  21. Create a RenderSettings node and connect it to rod_mtl_select_plane

  22. Set the interactiveOutput parameter to all. This allows seeing all render elements in the Monitor for interactive renders

  23. Render

The image below shows the result of the setup above (I've added another poly sphere object to make the scene a bit more complex)