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Many Boris Continuum Complete filters include the integrated motion tracker. Version 3.0.2 introduces significant improvements to this feature. Since the Motion Tracker works differently in each host application, filters now include a host-specific motion tracker help file. Press the Help button in the Motion Tracker banner for details. New onscreen tracking marks indicate which frames have been tracked.

In addition to the integrated Motion Tracker, BCC also includes a Witness Protection filter which lets you highlight or obscure an area. For example, track a t-shirt and obscure its logo with a blur. This tutorial uses the Witness Protection filter to obscure an ad on the front of a trolley. This tutorial uses a QuickTime movie as example footage. The clip was provided courtesy of ArtBeats. However, you can use any clip that you like.

Instructions

1. Click to select the clip in the timeline that you want to track.
2. Choose Effects > BCC3 Effects > BCC WitnessProtection.
   The Effect Controls window opens and the BCC Witness Protection filter displays.
3. Choose the appropriate effect from the Effect Method menu. This tutorial uses the Mosaic
   to obscure an advertisement. However, you can use whichever effect you like. You can apply a mosaic, blur, tint or brightness/contrast effect to the specified area.
4. Click the disclosure triangle to open the Mask parameter group. You will use the parameters in the Mask parameter group to set up the region that you want to obscure.
5. Use the onscreen crosshair control or the Offset X and Offset Y parameters to position the mask over the area that you want to obscure. This example will obscure the blue advertisement on the right front on the trolley.
   
6. Adjust the Region Radius to sets the size of the area to obscure. This example uses a value of approximately 6.

In this example you need to animate the size of the Region Radius, because the target region grows larger as the trolley moves closer to the viewer. In your image, the size of the area to obscure may remain constant as it moves across the screen.

6. It may be difficult to see the area that is affected. Setting the View Mask menu to Chosen Pixels or Mask Unchosen Pixels can help you to fine tune the area. View Chosen Pixels displays the matte in black and white. Black regions represent the unfiltered pixels; white regions represent the filtered pixels. Gray areas represent partially filtered pixels. This is useful for adjusting an area that is difficult to see, for example a subtle Blur. Mask Unchosen Pixels displays a 50% red mask over the unfiltered pixels. This is also useful for adjusting an area that is difficult to see.
   
7. Adjust Stretch to fine tune the shape of the masked area. Stretch distorts the oval-shaped region by stretching it either horizontally (positive values) or vertically (negative values). This example doesn't use the Stretch parameter.
8. Return the View Mask menu to Output.
9. Click the disclosure triangle to open the Effect parameter group. You will use the parameters in the Effect parameter group to fine tune your effect.

• When Mosaic is chosen, Amount/Brightness sets the pixelation along the horizontal and vertical axis. Set this value to approximately Contrast/Scramble shuffles the pixels in the image. As Scramble increases, the pixels become increasingly random. Increase this value to approximately 35.
• Seed determines which value is input to the random number generator used to scramble the pixels. If you like, you can adjust this parameter.
• The Color controls have no affect when Mosaic is chosen.

11. Click the disclosure triangle to open the Motion Tracker banner and its parameter group. You will use the parameters in the Motion Tracker parameter group to setup the Target. The Target indicates the area in the media to track. A good target region contains a high-contrast object with good vertical and horizontal edge definition. Ideally, you should find a pattern that is visible in every frame.
12. Move the current-time marker to the first frame of the effect and select the Track On-the-Fly checkbox. A white rectangular outline indicates the target area that will be tracked. When you select this checkbox, the effect no longer displays. Once you finish tracking, deselect this checkbox to play the applied effect.
13. Create a keyframe for the Tracker Center KF. This is important if you need to adjust the tracker later in your effect. BCC only creates Hold keyframes for this parameter within After Effects.
14. Set up the Tracker Center KF at the first keyframe. These controls set the area to track. In general it is easier to use the onscreen point controls. Then use the position controls for fine tuning.
15. Adjust the Target Size. This sets the size of the area to track. Increasing this value increases preview time but can increase the accuracy of the tracking. However, if you make the area too large, a similar pattern might accidentally be tracked.
16. Analyze the motion by clicking Play. The filter generates tracking data.

If the effect loses tracking, see "Correcting Motion Tracking Errors" for details on resetting the Tracker Center KF control to the location of the tracked object.

17. Deselect the Track On-the-Fly checkbox. The effect that you created now uses the motion tracker data to follow the target area.
    
18. Render the effect just as you would render any After Effects effect. Target area to track.

Correcting Motion Tracking Errors

It may be necessary to adjust the tracking during an effect, as the tracking can become inaccurate when the tracked object changes orientation or is obscured by another object. The best way to deal with this is by keyframing the Track Center KF control. The Motion Tracker only creates Hold keyframes for the Track Center KF parameter in After Effects.

• At a frame where the effect loses tracking, create a new Hold keyframe at the location of the object and continue tracking.
• If the object goes behind another object for several frames, you can put a Hold keyframe at each frame where the object is obscured.

The onscreen Tracker Center KF crosshair control does not follow the tracked object, but you can reset it to the location of the tracked object at any point in the effect.

Understanding the Onscreen Tracking Marks

When Track on the Fly is enabled, a line along the bottom of the Composition window indicates the location of tracked frames. The line references the length of the original source clip. It is important to note that this line is actually rendered onto the image when in Track on the Fly mode. Turn off Track on the Fly before you render to disk or export your effect.

• A Red mark along the bottom of the window indicates the current position of the current-time marker.
• Blue marks indicate keyframe locations. A keyframe location is any frame whose position differs from that of the previous frame. A frame where the center position differs from the previous frame is also considered a keyframe.

The blue onscreen marks are internal to the Motion Tracker. While the Motion Tracker considers these frames to be "keyframes", these are different than the After Effects keyframes.

1. Green marks indicate the frames that are currently tracked (i.e. the location of the tracker center has not changed since the tracking data was generated).
2. Magenta marks indicates frames which were tracked, but for which the tracker point has changed. This usually indicates a region that needs retracking (unless you are manually positioning the Tracker Center KF without making keyframes in your timeline).

Track On the Fly marks on the bottom of the Composition window

When you track an effect, marks for each tracked frame draw on the left of the current-time marker because there is tracking data for these frames.

Understanding Error Messages when Tracking on the Fly

The most common error message you will see during tracking is a "Please Move the Current-Time Marker..." error message. Several actions can cause this error message to appear.

• If you move forward in the effect past the end of the tracked region.
• If you play, but don't play every frame (Preview to Ram with Shift-0).
• If you partly track an effect, disabled Track on the Fly, and moved the current-time marker past the tracked region before re-enabling Track on the Fly.
• This message will sometimes appear when you press the space bar to stop playback. When this happens, the tracker render for the current frame is interrupted. Move the current-time marker back one frame and follow the onscreen directions to clear the cache to continue.

When you get this error message, perform the following steps.

1. Move the current-time marker to a previously tracked frame in your effect.
2. Clear the cache that After Effects has created. To clear the cache, press the Reset button then toggle a checkbox off and on, or change an unused parameter in the effect. If you try to retrack without completely clearing the cache, the motion tracker will not work when it reaches the frame that displayed the error message since that frame has already been cached.

Do not choose Edit > Purge > Image Cache to clear the After Effects cache for the Motion Tracker as that would also purge other items that you want to keep (rendered frames in other layers, precompositions, decompressed video).

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