This page gives information on the Object ID Render Element.
The Object ID Render Element isolates individual objects with colors or integer values for compositing purposes.
In 3ds Max, each object can be assigned an Object ID in the Object Properties dialog's G-Buffer section. This value is also sometimes called the G-Buffer value. Two or more objects in the scene can share the same Object ID.
The Object ID Render Element creates selection masks based on Object ID. This render element either shows each object (by Object ID) in a solid unshaded color, or stores the Object IDs as integer values within the EXR format or V-Ray Image Format file.
The Color (with AA) method supports antialiasing at the edges of objects. The Integer (no AA) method, which assigns an Object ID to each pixel in the render element, does not support antialiasing as each pixel either has an integer assigned to it, or it does not.
More than one VRayObjectID pass can be generated for a single rendering if desired; for example, if you wish to have both solid-shaded color and integer-based render elements for maximum flexibility during compositing.
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 are 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 are 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. This method is used to isolate and color correct the ottoman in the example. The ottoman has an Object ID of 1, the floor has an Object ID of 4 and the walls have an Object ID of 2. See how the render looks before and after compositing.
If antialiasing is needed for a scene, setting Output type to Color (with AA) gives the best results.
Setting the Output type to Integer (no AA) renders slightly faster, although with no antialiasing.
The name of the Object ID render element must consist of the name of the Object ID itself, a dot and then any other string to be properly read in Nuke. For example, VRayObjectID.example . Do not include numbers in the name.