About key points

Key points are the basic elements of the 2D tracking. Key points can be inserted in any image and anywhere within the image. For each track point the following information is shown in the Track window. See The Track View.

If a point is computed, the shape indicates that MatchMover has generated the point. Computed points appear red if bidirectional tracking is only partially completed. There are five key types and each key type has a different symbol.

Shape	Type of Point
	Automatic - Defines a key point added automatically by the tracker when the quality falls below a defined threshold (if the Automatic Key Insertion option is selected in the Preferences).
	Start - defines the start of a track segment.
	End - Defines the end of a track segment.
	Intermediate - Default key type when you create a new track. Use this type of key to constrain the tracker so that it passes through important positions.
	Single - Defines a key point that you created manually. The data from this key point is ignored by the 2D tracking but used in the 3D tracking process. Use this type of key to correct the results of the 2D tracker at isolated frames without affecting the rest of the tracker, for example, if a track is obscured in a scene but it’s position is known.

In a 2D View, editing an auto-tracked point automatically turns it into a key point. When you create a key point, it has by default an intermediate key point type. You can create begin, end, intermediate, and single key points. If you edit an intermediate key, computation for the track will be lost if the “Auto Clean” option is set and tracking must be re-run. You can have several tracked segments for one track.

Editing a key point type

To edit a key point type, do one of the following:

Select 2D Tracking > Set Key.
Right-click in the 2D View, the Point Tracks folder in the Project window or the Track window to show the pop-up menu and select Set Key.

Choose the desired key type from Begin, Intermediate, End and Single. See About key points for more details on key types.

Notice that the key symbol changes (in the Track window), to show the new status of the key.

Inserting a new key point in a track

Select a track. Click and hold in the 2D View where you want to place the new key. By default MatchMover zooms in on the area using a pop-up magnifier.

NoteYou can replace the pop-up magnifier with the Magnifier Window to help you in placing a key point, see Magnifier window.

MatchMover places the key. The center of the key point is marked with a cross that is surrounded by two boxes. This is the Tracking Tool. See About the Tracking Tool. The key type symbol and its label are also displayed.

TipRepeat the procedure for other tracks in the same frame or for other keys for the same track in different frames. If you want to place other key points for the same track, you can use the Auto Key Match function.

In editing keys while a 2D View is in focus, you can use the arrow keys to move the current key. You set the number of pixels for each hit in the Nudge step box in Edit > Preferences > 2D Tracking. The value can be less than one pixel. See Configuring the tracker.

If the edited point was not a key, it is automatically turned into one.

TipPressing shift with an arrow key will multiply the nudge step by 10.

Moving a key point

Select the key point you want to move. The pointer changes to .
Drag the pointer to the new position and release.
NoteIf Auto Clean is enabled, this action deletes the 2D computed points that have been created from this key. To recompute these points, you have to rerun the tracking process. To enable or disable Auto Clean, select Edit > Preferences > 2D Tracking and click the corresponding box.

Deleting a key

Select a track then a frame if none is selected.
Do one of the following:
- Select 2D Tracking > Clear Keys.
- Right-click in the 2D View or the Point Tracks folder in the Project window or the Track window to show the pop-up menu and select Clear Keys.

If you have not created a time range, MatchMover deletes the key at the current time. If you have created a time range, MatchMover deletes all keys within the time range.

Using the Auto Match Key

The Auto Match Key uses the pattern around the position of the previous key and attempts to find a similar pattern at the current frame. If you do not use the Auto Match Key option, you have to be careful to place a key point exactly in the position so that it matches the position of the previous key in the same track. The area to search is defined by the value in pixels in the First Pass field. The default value is generally sufficient.

For example, place a key point in frame 1. Then move to frame 5 where you place another key point. In Auto Match Key mode, clicking near to the original key point is sufficient for MatchMover to place the new key in the right position.

To toggle the Auto Match Key option for the current key point, press Shift+click.

If you want to enable the Auto Match Key permanently:

Select Edit > Preferences and open the 2D/Auto Tracking page.
Check the Auto Match Key check box.

MatchMover now uses this function when you place a key.