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Using Mattes From the Fusion Page
If you’re grading a composite that’s been created in the Fusion page, you can feed mattes created in different parts of a Fusion composition to the Color page to use in the grade as well. For example, if you’re grading a composite of a foreground actor who’s green screen keyed against a background layer, you might want to use the matte generated for the key to protect the foreground subject from an operation in your grade that you only want to affect the background. Happily, this is easy to set up.
In the following Fusion composition, two DeltaKeyer nodes (one to create an overall matte, and one to create a solid matte protecting the core) and one BSpline node (to create a garbage matte) work together to create a finely-tuned matte. This matte is used by the Merge1 node to preserve the subject’s hair and composite them in front of a gently blurred (using the LensBlur node) planet, with the final result connected to the MediaOut1 node, which feeds this image to the Edit page and Color page for continued adjustment.
A green screen composition in the Fusion page, outputting the RGB in MediaOut1, and the foreground matte in MediaOut2
Because the Merge1 node outputs the entire composition as a single image, a second MediaOut node (highlighted) is added to output the matte, just in case the colorist might want to use it later.
TIP: In this composition, the foreground and background images are different sizes, so outputting the alpha channel of the DeltaKeyer1 node would result in a matte sized to match the foreground image, but that doesn’t fit the composition, which is cropping
the top and bottom of the foreground image based on the frame size of the widescreen background image. To get around this, the foreground and background images are composited a second time using the Merge2 node, which has the Operator parameter set to “In” to output just the foreground image and matte, as resized by the Merge operation. The resulting MediaOut2 node thus outputs a foreground matte that’s properly sized to fit the composition.
TIP: In this composition, the foreground and background images are different sizes, so outputting the alpha channel of the DeltaKeyer1 node would result in a matte sized to match the foreground image, but that doesn’t fit the composition, which is cropping
the top and bottom of the foreground image based on the frame size of the widescreen background image. To get around this, the foreground and background images are composited a second time using the Merge2 node, which has the Operator parameter set to “In” to output just the foreground image and matte, as resized by the Merge operation. The resulting MediaOut2 node thus outputs a foreground matte that’s properly sized to fit the composition.
TIP: In this composition, the foreground and background images are different sizes, so outputting the alpha channel of the DeltaKeyer1 node would result in a matte sized to match the foreground image, but that doesn’t fit the composition, which is cropping
the top and bottom of the foreground image based on the frame size of the widescreen background image. To get around this, the foreground and background images are composited a second time using the Merge2 node, which has the Operator parameter set to “In” to output just the foreground image and matte, as resized by the Merge operation. The resulting MediaOut2 node thus outputs a foreground matte that’s properly sized to fit the composition.
On the Color page, the grade in node 1 is applied to the overall final result, which is a single image. After grading, it’s decided that the woman appears a bit warm relative to the cool blue of the planet behind.
The composition as it appears in the Color page Node Viewer
Right-clicking the background of the Node Editor and choosing Add Source adds a second source at the left of the Node Editor.
Adding a source to bring in the MediaOut2 node’s matte output from the Fusion page composition
This second source corresponds to the second MediaOut node you added to the Fusion page composition, which outputs the Matte as a key in the Color page, usable just like any other key. If you hover your pointer over each source, a tooltip appears letting you know which output corresponds to which node.
