This page provides information on the MultiMatte Render Element which creates red, green, and blue selection masks based on an object's Object ID or Material ID.
Overview
With the MultiMatte Render Element, only three colors are possible: red, green, and blue. In comparison, other matte render elements can include a multitude of colors to represent each material or object in a scene with a different color. 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 Render Element includes anti-aliasing.
To represent all the objects or materials in a scene with just the available red, green, and blue colors, several MultiMatte Render Elements can be generated for a single rendering, each with different Material ID or Object ID settings.
Attributes
Name – The text added to the end of the rendered file, when saved as a separate file (e.g. myrender.MultiMatte.vrimg).
Red ID – Sets the ID used for the red channel.
Green ID – Sets the ID used for the green channel.
Blue ID – Sets the ID used for the blue channel.
Use Material IDs instead of Object IDs – When disabled, MultiMatte considers the Red object ID, Green object ID, and Blue object ID values to be the Object ID and renders the R, G, and B channels accordingly. When enabled, these values are considered to be the Material ID.
Include Matte Objects – Determines whether to include matte objects when generating the render element. A matte object is an object that has been assigned a Wrapper Material with Matte surface option enabled.
Consider for Anti-Aliasing – When enabled, Anti-Aliasing is used where possible.
Deep Output – Specifies whether to include this render element in deep images.
Common Uses
The MultiMatte Render Element is useful for isolating geometry or material 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 or materials 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 Red ID to match the ceiling's object ID, the Green ID to match the stone fence's object ID, and the Blue ID to match the floor's object ID. Thus, masks are created in compositing to modify the isolated geometries. See the render before and after compositing.
