This page gives information on the Object ID Render Element.
||Render Setup window|| > Render Elements tab > Add button > VRayObjectID
This render element is enabled through the Render Elements tab of the Render Setup window in 3ds Max and displays its parameters in a rollout at the bottom of the window:
vrayVFB – When enabled, the render element appears in the V-Ray frame buffer.
deep output – Specifies whether to include this render element in deep images.
output type – The type of output desired:
Integer (no AA) – Object IDs will be exported within the EXR or V-Ray Image format image as an Integer value, one integer per pixel. Colors shown in the V-Ray Frame Buffer are for visual representation only, and are not saved as part of the render element file itself. Antialiasing around the edges of the object or material is not represented.
Color (with AA) – Each object ID renders as a solid color depending on the Object ID set in the 3ds Max Object Properties dialog. A wide range of preset colors is used (red, green, blue, pink, purple, orange, etc.) to accommodate a potentially large number of Object IDs in the scene. The edges of objects or materials are antialiased where they meet other parts of the scene. The colors red, green, and blue will be used first, followed by additional colors if there are more than three Object IDs in use in the scene.
The Object ID Render Element is useful for isolating geometry in a scene based on the Object ID. This means that items can be isolated by use of a matte created from the solid colors within the Object ID pass. In the example below the sofa has an Object ID of 1, the dangling light has an Object ID of 4 and the sideboard has an Object ID of 2.