Layering
Clips
The layering
of clips is the essence of compositing. In Houdini , you can use
the Layer COP to bring together several operations. Using the Viewer
pane, you can create several clips then interactively select and
layer them. This results is a network of composite operations that
feed into a Layer COP.
1.
Setup
Select Settings
> Composite Project. Set the Resolution
to 512, 512.
Click Accept.
These Project settings will
affect how new clips are created.
Select Network
> Compositing (COP) from the Viewer pane
menu. This takes you to the top level of the img folder. Press i
to go into img1. You can set up several composites
within one scene file. Each one would need to be set up as a separate
Image Network.
2.
Import a Ramp
Background
In the Viewer
pane, press tab > Generator >
Ramp. This creates a Ramp COP that has a resolution
of 512, 512.
In the Viewer
pane, click in the middle of the screen to add a third ramp point.
Alt-click
on the Points icon and change its color. Repeat
for all the points. In the Parameter pane, click on the Ramp
tab and set Rotation
to 30.

3.
Create a File Image
In the Viewer
pane, press tab > Generator >
File. MMB-click
to accept this and add it to the Viewer pane. Now you can see both
COPs. Use the MMB
to zoom out. Use the Link Scrolling
button to zoom them together. This File COP
is referencing the default butterfly image which you will use in
this lesson.

4.
Create some Text
In the Viewer
pane, press tab > Generator >
Font. MMB-click
to accept this and add it to the Viewer pane. Again the node is
created at 512x512 to match the Project defaults. Now you can see
all three COPs in the Viewer pane.
In the Parameter
pane, change the entry in the Text
field then choose a Font
that you like.

5.
Layer the Three clips
In the Viewer
pane, press tab > Generator >
Layer. LMB-click
on ramp1 to choose this as the background then click
on font1 and default_pic as the
foreground layers. Text will show up on the clips to indicate they
have been chosen for layering.

MMB-click
to accept. The layer1 clip is placed into the Viewer pane alongside
the original operators.

6.
Reorder the clips
In the Parameter
pane, you can reorder the clips by clicking on the up arrow found
on the left of each layer's listing in the Input Operator list.
The top operator is the background. The other operators on the list
have arrows and are designated as Layer 1, Layer 2... If you click
on the Transform tab, there are sub-tabs for each
of these layers.

Press the t
key in the Viewer pane to focus on the layer1 clip.
The other clips are shown as tabs along the bottom of the pane.

7.
Render out the Results
In the Network
pane, select Network > Outputs.
Press tab > Generators > Composite.
In the Parameter pane, set the COP name to layer1
then click the Render
button to render to an mplay window. You can also set up the
Output Picture to render out a sequence of images.

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