Choosing good points

Always play back your shot and plan which points you should track. This step is critical in order to provide track points useful to the solver. You can use the Playblast or Time Slider to play the shot. For more information about playback tools, see Live playback tools.

What helps the solver:

Choose features that are stationary or fixed on an object.
To solve for camera movement, the track points must be stationary. To solve for object movement, the track points must be fixed relative to the moving object. For example, if you are tracking the movement of a car, a feature on a headlight would help, but not a feature on an antenna waving in the wind.
Choose features that you can later constrain to a survey measurement.
When you solve, you can get improved results using survey constraints, so choose features with constraints in mind. The survey constraints are: Plane (such as a floor, table, or wall), Point (a 3D coordinate, such as a point corresponding to a position on reference geometry), Distance (measurement between points), and Depth (distance from a point to the camera). For more information, see Constraint strategies.
Choose features with long duration of visibility.
The more frames the feature is visible, the better. For example, in a 100 frame shot, it should be visible for at least ten to twenty frames. Also, avoid features that come in and out of view too much.
Choose features spread throughout the width, height, and depth of the scene.
The solver needs a “balanced diet” of features from various areas, not just features grouped in one region.
Choose features in the area where the 3D model will be in the scene.
In addition to tracking a variety of areas, you may want to track additional features around the intended 3D object location. If you intend to import the 3D model into the scene, look for points that clearly correspond to points on the model.
Choose features that cover a range of motion.
For example, if the shot is a slow pan from left to right, choose features in the center that overlap the start and end of the shot.

What helps the tracker

Choose features with distinct shape or high contrast.
To establish a lock on the target, the tracker uses both the object’s shape and contrast with the background. Tracking artificial markers is helpful, but natural features work as well, such as tree branches, rocks, and windows. An object that has a definable tip can be easier to track.
Choose larger objects if possible.
In general, tracking larger objects gives more accurate results than tracking small objects. However, a larger target means the tracker may fail sooner due to pattern changes.
Avoid features that change shape radically.
Avoid shifting backgrounds and highlights within the target area (inner box).

Example track points

The following illustration shows some of these principles. The points are stationary and spread throughout the breadth and depth of the scene. There is an emphasis on the fence because it is where the CG fence will be placed and because the flat geometry allows you to use a plane constraint.