Using the BCC Matchmove Filter in Final Cut Pro

Media Used in this Exercise:

We're going to use the BCC Match Move filter to match the camera pan movement of one clip to that of a clip which was shot with a locked down camera and generate a seamless composite of the two clips making them appear as though they were shot with the same camera - all right within the Match Move filter. We'll start the project by importing the two clips that we need into a new project in FCP. Let's take a look at the two clips that we are using - one is a crane shot of a street scene of a clock taken on Fisherman's Wharf in San Francisco while the other is an underwater scene of a fish swimming near some coral along the California coast. In the crane scene, there is a clock on a post and we are going to comp the fish scene into the clock face. The fish clip has a circular alpha cut-out shape so that only the pixels within the circle are opaque.

To start, we drag the background clip with the clock into the timeline on video 1 track, we don't need to pull the fish clip into the timeline as we can use the filter wells to pull the clip directly from the project window. Let's review the movement of the clip in the scene - there is a slow camera crane up that we will capture with the BCC Match Move filter. We'll set the current frame indicator to the start of the clip. Then we add the BCC MatchMove filter by selecting it from the effects tab and dragging it onto the clock clip in the timeline. We then select double-click the clock clip in the timeline to bring it into the source monitor window, and click the filters tab to access the filter parameters.

Now let's track the background clip. Click on the Hide Motion Tracker button in the filter UI to reveal the motion tracker parameters. By default the filter will set itself to track the clip to which it was applied and in this case that it what we want to do, however it is possible to track and recover the motion from one clip, then apply that tracking data to composite two entirely different clips together. For this exercise, we will drag the clock clip from the project window onto the Tracking Source Layer input well. Next we'll enable the Track On The Fly option by clicking on the button with the same name in the filter UI. Set the tracker target to look at the bottom of the letter F on the clock face by setting the following values in the Tracker Center KF numeric entry boxes: +236, -165. Set the Target Width parameter to a value of 15 and leave the Search Width at it's default value of 40.

Using the right arrow key on the keyboard, step through the timeline frame by frame until you reach the end of the clip. This process tracks the target as it moves across the record monitor and feeds the recovered motion to the filter. There are indicators at the bottom of the composite window that provide information regarding the integrity of the tracking process - a solid green bar indicates that all frames were tracked, while the color purple is used to indicate a non-tracked frame. A red bar is displayed to indicate the current time. When tracking has completed, you may want to monitor the tracker running through the frames to make sure that the tracker did not drift or move off target. Once satisfied with the tracking data, you can disable the track-on-the-fly feature.

So ... now that we have recovered the camera motion, we need to instruct the filter to use this motion to control the movement of the foreground clip in the composite, which in this case is the fish clip. Click on the Hide Motion Tracker to hide the motion tracker parameters and click on the Hide Match Move Controls to reveal the match move parameters. Drag the fish clip from the project window onto the MM foreground image well to set the MM foreground to the shot of the fish. The fish will move correctly now to match the camera movement from the background clip, but it is not in the correct position over the clock face that we wanted to comp it onto.

Move the CTI to the middle of the clip. We'll reposition the fish so that it is positioned over the clock face. The fish will move correctly now to match the camera movement from the background clip, but again it is not in the correct position over the clock face. We'll reposition the fish so that it is more closely aligned with the clock in the background. By using the offset parameters from the motion tracker group, we can change the relative position offset of the foreground clip to the recovered tracker data. Remember that we tracked the letter at the bottom of the clock and now the center of the fish precomp is locked to the letters so we just want to offset the tracker data as a group. We'll set the offset x to 0.050 and the offset y value to -0.330. This places the fish with alpha directly over the clock face. But there is perspective distortion in the background shot that we need to apply to the foreground to make a convincing composite. To fix this, we let the filter do the work by using the built-in DVE controls to match the perspective in the background shot.

Hide the controls for both the Motion Tracker Group and also the Match Move group. Then reveal the parameters from the Transform control group by clicking on the Hide Transform Controls button. This is where we apply transform operations to the foreground clip. First unlock the scale and set the scale x to 74 percent and the scale y to 84 percent. Observe now that we're getting close to a match. Set the Tumble parameter to -11 and the Spin parameter to + 33 degrees. Bingo - the foreground clip now sits right on top of the background clip with matching perspective distortion.

Now we'll just go in and blend the edges of the foreground clip so that it looks like the two clips are one shot. The controls for this function are located in the Composite group. Hide the Transform Controls and reveal the parameters in the Composite group by clicking on the Hide Composite controls and then reveal the Light Wrap controls and set the Wrap Softness to 10 and the Wrap Width to 3. Play back the result and observe that the foreground clip is locked to the background clip in a seamless composite.

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