In this section of the lesson, you will add three tracks that correspond to points in the scene’s static background. This is the minimum number of points required to define a coordinate system. Creating these tracks defines a 3D coordinates with respect to a world coordinate system attached to the background, which is very useful in motion capture. This step might not be necessary if all you need is to compute the 3D trajectories with respect to an unspecified coordinate system

In the last step of the lesson you will create skeleton lines which will better display the motion captured and of the tracked scene.

Since there are 18 markers attached to the actor, each potentially a track point, you can either continue adding tracks to your current project, or you can open Actor_tracked.mmf which has tracks already created for all 18 markers. This file can be found in the Tutorials/Mocap directory.

You can also start this section of the lesson using Motion_solved.mmf. In this file, six markers have been tracked. This file can be found in the Tutorials/Mocap directory.

If you want to add the tracks yourself, do so before continuing the lesson.

To create point tracks in the background

1. In the Project window, select the Point Tracks folder.

   Since the point tracks that you will create for the background are for static, rigid objects, selecting the Point Tracks folder ensures that your new point tracks are not added to the Actor Point Tracks folder.

2. In the first frame of Sequence01, place a track point on the floor of the scene by selecting 2D Tracking > New Track or clicking the New Trackicon.

   You can try to use the square patterns to locate easily recognizable locations on the floor as you will need to place a track point in the same location in Sequence02.

   Note

   You can try to use the square patterns to locate the points on the floor. Once the first track is placed, you do not need to run the Track Forward on it, because the sequence was shot with a fixed camera, and MatchMover detects this through the "fixed" motion constraint.

3. In the first frame of Sequence02, place the same track point in same location as you did in the first frame of Sequence01.

   This point is reconstructed in space right away, based on the existing camera calibration (solve). If the point is in the wrong location in one of the sequences, the cross-hairs will appear in red. This can often happen if your video sequences are low-resolution, compressed footage.

4. Repeat steps 2 and 3 to create the remaining two track points for Sequence01 and Sequence02.

   The goal is to place track points that define a coordinate system on the ground.

   
5. Solve for the camera by selecting 3D Tracking > Solve For Camera or by clicking the Solve For Camera icon.

   The camera is calibrated with the a coordinate system on the scene’s background. You can now finalize you project by building some skeleton lines.

6. Click the 3D space icon that is located in the top left corner of both viewports.

   The view switches to 3D mode. A camera icon and grid is placed in the Workspace.

   You can also switch back to a single viewport by selecting Single Viewport Space from the Toolbar.

7. In the viewport, select the yellow cone that appears at the right side of the actor’s head.

   This cone represents Track01.

8. Shift-select the yellow cone that appears at the left side of the actor’s head.

   This cone represents Track02.

   
9. With both cones still selected, select 3D Tracking > New Relation.
10. In the Parameters window, click the Relation 01 tab.
11. From the Type list, select Line.
    

    A line is displayed between the two cones.

12. Repeat steps 7 to 11 for the remaining track points or until you see satisfied with the line reconstruction of your motion capture.

You can export your project to a file format supported by your favorite animation or composition software by selecting File > Export.