This page provides information on the MultiMatte Objects Render Element.
Overview
The MultiMatte Objects Render Element creates red, green, and blue selection masks based on an object's Object ID. This render element uses only three colors for masking: red, green, and blue. It analyzes the scene at render time and automatically creates the necessary number of channels based on the number of unique specified IDs. Each channel holds up to 3 unique IDs. Each channel's name indicates the IDs it represents.
With MultiMatte, a single R, G, or B channel can be used directly as a matte, eliminating the step of selecting the color in the compositing software. This ease of use makes MultiMatte a popular choice for compositors.
The MultiMatte Objects Render Element includes an option for antialiasing.
Besides this render element, V-Ray also supports MultiMatte Materials channel, which uses Material ID numbers.
UI Paths
||V-Ray Asset Editor|| > Render Elements (right-click) > MultiMatte Objects
||V-Ray Asset Editor|| > Create Asset (left-click) > Render Elements > MultiMatte Objects
How to Set Object Ids
Object ID can be set from the context menu (right-click on a selected object) > V-Ray Object ID > Selection > Set.
You can set the same object ID for a group of objects in order to create a mask with the MultiMatte Objects Render Element.
The example here shows setting the same object ID for the three chandeliers. This way, they receive the same color in the MultiMatte Objects channel and can be used as one object in compositing.
See the rendered result below.
Setting Object IDs in the viewport
Result in the MultiMatte Objects channel
Common Uses
The MultiMatte Objects Render Element is useful for isolating geometry in a scene. While other matte render elements perform similar tasks, MultiMatte is often quicker to use in compositing software because it can be made to include only pure red, green, or blue channels to represent objects in the scene. Compositing software often has a feature for easily selecting the red, green, or blue channels in an image for use as mattes.
In this example, we set the ceiling object ID as 1, the the stone curtains object ID as 2, and the floor object ID as 3. Thus, masks are created in compositing to modify the isolated geometries. See the render before and after compositing.
