A nice 3D effect is the ability to have two videos fly
through space parallel to each other. The secret to controlling
multiple tracks in unison is to use Parent Motion. For this to
work in 3D, all three tracks must be in 3D mode. Let’s see how
it’s done.
We start by pressing Ctrl+Q three times to add three
tracks to the Vegas timeline. We’ll name these “3D Parent”,
“Front Plane” and “Back Plane”.
For this tutorial we will add Generated Media but you
can use any video you want. Let’s add a Sony Text Generated
Media on each track. We’ll also
change the background color of the Generated Media Text to make it more easily
identifiable.
Next we want to change the Compositing Mode for all
three tracks to 3D Source Alpha. To do this Press
the Composite Mode button in the track header and
select 3D Source Alpha from the dropdown list.
Your tracks should look like the image below with all
three in 3D Composite Mode
Now that all three tracks have Track Motion set to 3D
Source Alpha, let’s go back to the bottom track (3) which holds
the Back Plane and push it back in 3D space. Press
the Track Motion button on track 3 and in the
Track Motion window, set the Z Position to 240. This
will push the video for that track back.
Now to control the two tracks in unison we do two
things. First make tracks 2 & 3 a child of track 1 using the
Make Compositing Child button for both tracks.
Press the Make Compositing Child button in the
track header for tracks 2 & 3.
Your tracks should now look like this:
Next we need to use Parent Motion to
control the child tracks. Press the Parent Motion
button to bring up the Parent Motion window.
This brings up the Parent Track Motion window.
First place the interface in 3D Source Alpha
mode by pressing the Source Alpha selection dropdown in the
upper left corner of the interface and selecting 3D
Source Alpha.
Now you can spin the cube in the large window in 3D
space and your two tracks will spin about as well always
maintaining 240 units of Z space between them.
Here is the preview window based on these settings
That's all their is to it. You should be
able to use this same technique to build things like a cube of
video and control all sides at the same time using 3D Parent
Motion. Here is a small video I made of this project using some
keyframes on the 3D Parent track.
