User Manual

Using a Matte to Create Transparency
If you’ve been provided with a separate Matte clip for defining clip transparency, you can use
that Matte clip within the node tree of a superimposed clip to create a composite using the
Alpha Output.
To create a composite using an external matte:
1 To associate an external matte with a clip, open the Media page, select the clip you
want to add a matte to in the Media Pool, navigate to the matte file using the Library
browser, and then right-click the matte file and choose Add as Matte. For more
information on importing mattes, see Chapter 126, “Combining Keys and Using Mattes.”
2 Open the Color page and select the foreground clip in the Thumbnail timeline, then
right-click Node 1 in the Node Editor and choose the matte you added from the Add
Matte submenu.
An EXT MATTE node appears underneath Node 1, with the first of its four key outputs
connected to Node 1’s key input. (Working with external mattes is covered in more
detail in a prior section of this chapter.)
3 Now, right-click anywhere within the node graph (other than on a node) and choose
Add Alpha Output from the contextual menu.
An Alpha output appears underneath the Node Tree output.
4 Drag a connection line from the second key output of the EXT MATTE node to the
Alpha output.
Using an external matte in the grade and to the Alpha output
You should now see a successful composite, with the external matte creating a
regionof transparency in the foreground clip through which the background clip
shows through.
Before and after the final composite, created by connecting an
EXT MATTE node to the Alpha output in the node graph
Chapter – 127 Channel Splitting and Image Compositing 2889