User Manual

If you specify the dimensions of the background image in the Reference Size controls,
this changes the way the center control values are displayed so that it shows the actual
pixel positions in its X and Y fields.
Extending the example, set the width and height to 100 each and the center will now be
shown as 50, 50, and we would move it 5 pixels toward the right by entering 55, 50.
Internally, the Merge node still stores this value as a number between 0 to 1 and, if the
center control’s value was to be queried via scripting or the center control was to be
published for use by other nodes, the original normalized value would be retrieved. The
change is only visible in the value shown for merge center in the node control.
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Use Frame Format Settings: Select this to force the merge to use the composition’s
current frame format settings to set the reference width and reference height values.
 Width and Height: Set these sliders to the width and height of the image to change the
way that Fusion displays the values of the Merge node’s center control.
Channels Tab
The Channels tab has controls that let the Merge node use Z-channels embedded within each
image to define what’s in front and what’s behind during a Merge operation. The following
controls let you customize the result.
 Perform Depth Merge: Off by default. When turned on, the Z-channel of both images
will be used to determine the composite order. Alpha channels are still used to define
transparency, but the values of the Z-Depth channels will determine the ordering of
image elements, front to back. If a Z-channel is not available for either image, the
setting of this checkbox will be ignored, and no depth compositing will take place. If
Z-Depth channels are available, turning this checkbox off disables their use within this
operation.
 Foreground Z-Offset: This slider sets an offset applied to the foreground image’s Z
value. Click the Pick button to pick a value from a displayed image’s Z-channel, or enter
a value using the slider or input boxes. Raising the value causes the foreground image’s
Z-channel to be offset further away along the Z-axis, whereas lowering the value
causes the foreground to move closer.
 Subtractive/Additive: When Z-compositing, it is possible for image pixels from the
background to be composited in the foreground of the output because the Z-buffer for
that pixel is closer than the Z of the foreground pixel. This slider controls whether these
pixels are merged in an Additive or a Subtractive mode, in exactly the same way as the
comparable slider in the Merge tab.
When merged over a background of a different color, the original background will still
be visible in the semitransparent areas. An Additive merge will maintain the
transparencies of the image but will add their values to the background.
Chapter – 86 Composite Nodes 1916