Getting Started > Tutorials > Lesson 4: Motion capture  > 
Creating motion tracks
 
 
 

In this section of the lesson, you create a motion track of the actor’s movements.

NoteYou can bypass this section of the lesson by opening Motion_solved.mmf.mmf. This file can be found in the Tutorials/Mocap directory. You can then proceed to Finalizing your motion capture project.

The first step in this process is to create a new point track group that you will use to place the actor's tracks.

To create a new point track group

  1. In the Project window, right-click the Point Tracks folder and select New Group from the pop-up menu.
  2. In the Parameters window, click the Group 01 tab.
  3. In the Label field, select Group 01and type Actor.
  4. In the Options section, select Non-rigid (motion capture) from the Motion list.

    This option specifies that the point track belonging to the new group will be for the motion of non-rigid objects.

Creating point tracks

In this section of the lesson, you place track point on markers that are attached to the actor. There are 18 markers attached to the actor, but for this section of the lesson, you use only six for your tracking points. When creating a motion track, you must place your track points on the same marker in both sequences. For example, if you place Track 01 on the white marker located on the right side of the actor’s head in Sequence01, you must also place Track 01 on the same marker in Sequence02.

Be aware that some tracks may need manual adjustment as can be the case when using supervised tracking. For example, in a few of the frames, MatchMover confuses the motion of the actor's saber with the motion of the markers on the actor's leg and includes the saber’s motion in the track.

The easiest markers to track in both sequences are located on the actor's head and on the legs. In all cases, try to choose the most visible markers in your sequences.

For information about supervised tracking, see Lesson 2: Using supervised tracking.

To create the track points

  1. Go to frame 51 in the Time Line.

    The left viewport now displays the first frame of Sequence 01and the right viewport now displays the first frame of Sequence 02.

  2. Select 2D Tracking > New Track or click the New Track icon.

    When you drag the cursor over the Workspace, it changes to cross-hairs.

  3. In Sequence 01, position the cross-hairs over the white mark located on the right side of the actor's head.

    Use the Magnifier window view below the Project window to help you precisely position the location of the new point.

  4. Click to create Track01 for Sequence 01.
  5. In Sequence 02, position the cross-hairs over the same marker, and click to create Track01 for Sequence 02.

    Use the locations shown in the image below as a guide.

  6. With the track point selected, select 2D Tracking > Track Forward or click the icon to run 2D tracking for your points.
  7. Using steps 2 to 6, create five more track points.

    Your project should look similar to the one in image below.

Performing an initial solve

Before you can perform the camera solve, you must remove the two-frame shift between the two sequences.

The first two frames (0-1 in the Time Line) only appear in Sequence 01, and the last two frames (100-101 in the Time Line) only appear in sequence Sequence 02. Since no 3D information can be derived for these frames, you need to specify that the frames are not solved.

To solve for the camera

  1. In the Track View, Shift-select the time interval of the first two frames (0 and 1) of Sequence 01.

  2. Right-click in the Track View and select Set Frames > Do Not Solve from the pop-up menu.
  3. Repeat steps 1 and 2 for Sequence 02.

    For Sequence 02, select the time interval of the last two frames in the sequence (100-101).

  4. Deselect the time interval by Shift+right-clicking in the Track View.
  5. Solve for the camera by selecting 3D Tracking > Solve For Camera or by clicking the Solve For Camera icon.

    The camera is now calibrated.

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