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	Point from the list, and clicking the new location, or by changing the X and Y values.
	Click the Modify Camera button after moving the Camera Point’s position to realign the
	camera.
Caution	If you get an error, the camera is not created. The most likely error is that you have assigned
	a position to the wrong Camera Point. Check the positions of each Camera Point, and try
	again.

5.With the camera positioned to match the background, you can position the car so that it is correctly aligned with the other cars in the image. Select the Porsche model, scale it down, and position it in the Camera viewport on the road. Turn off the construction grid by pressing the G key on the keyboard.

Figure 25-2 shows our current scene from the matched camera perspective.

Figure 25-2: The matched camera view with a car inserted into the scene

Using the Camera Tracker Utility

The Camera Tracker utility recreates the movements of a camera that was used to create an animated background. As with the Camera Match utility, you access the Camera Tracker utility from the Utilities panel. Click the More button to open the Utilities dialog box, and select the Camera Tracker from the list of additional utilities.

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Loading a movie file

One of the first tasks is to load a movie file to track. You can do so using the Movie File button (initially labeled “none”) found in the Movie rollout, shown in Figure 25-3. This button opens the Browse Image for Input dialog box, where you can select a movie file to load. Usable formats include .AVI, .MOV, .FLC, and .IFL. After you select a movie file, the button’s label changes to the name of the movie file. The Movie rollout also includes a Display Movie button to view a single frame of the movie. The Show Frame value lets you display a specific frame of the movie.

You can set the Deinterlace option to Off, Odd, or Even and, if enabled, it de-interlaces a video file using odd or even lines. This feature enables you to view interlaced video segments whose individual frames include only odd or even lines. The Fade Display option fades the movie by 50 percent so you can clearly see the tracker gizmos. (See the next section for more about tracker gizmos.)

Figure 25-3: The Movie rollout lets you load and view a movie file.

The Movie rollout also includes buttons to Save, Save As, and Load camera tracker setting files, which are saved with the .MOT extension. The Auto Load/Save Setting option automatically saves these files in the same directory as the movie file; they are automatically updated when any of the settings change.

Working with trackers

The Camera Tracker utility uses Camera Points, just as the Camera Match utility does. Camera Points can be set up in the same manner discussed in the previous section. The Camera Tracker utility requires a minimum of six Camera Points and at least two that are in separate planes.

These Camera Points become the motion trackers for the utility. Motion trackers are points that are followed throughout the animation. These points are used to compute the camera’s path. You display and control these trackers using the Motion Trackers rollout, shown in Figure 25-4. To add a tracker to the list, click the New Tracker button. This places the tracker gizmo in the list. You can change the parameters for the gizmo and move the gizmo as needed.

The Scene Object button lets you select a Camera Point or some other object as the object to track. You can also specify values for Match Weights and Max Move per Frame. The higher the Match Weights value, the more consistent the track points in the scene are.

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The Set Start and Set Stop buttons let you set the frames at which the tracking starts and stops. If a tracking object moves out of the scene, click the Set Stop button at the frame where it disappears.

Figure 25-4: The Motion Trackers rollout lets you add trackers to the scene.

Using the tracker gizmo

The tracker gizmo looks like a box within a box. The crosshairs mark the center of the tracking object, the inner box (called the Feature Selection box) marks the edges of the tracking object, and the outer box (called the Motion Search box) determines the search area in which the tracker gizmo looks for the object in each frame. Figure 25-5 shows the tracker gizmo.

Feature Selection box

Motion Search box

Center of gizmo

Figure 25-5: You use the tracker gizmo to track objects through several frames.

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Stepping through frames

You use the Movie Stepper rollout, shown in Figure 25-6, to step through the animation frames. This feature is useful for ensuring that the tracking objects are visible throughout the entire animation. You can also use this rollout to manually set the tracking.

Figure 25-6: The Movie Stepper rollout lets you step through the movie frames.

The Movie Frame spinner displays the current frame. The buttons under the frame number let you move forward or backward through the frames. These buttons can move to the beginning frame, back ten frames, back one frame, forward one frame, forward ten frames, or to the last frame.

The Feature tracking button, when enabled, computes the tracking locations; the tracker gizmos move to their tracked positions if the positions have already been tracked. The Step Keyframes option lets you move between keyframes instead of frames using the stepping buttons. The Show Track option displays the path traveled by each tracker as a line.

Note Red track lines indicate that the tracker has been tracked. White track lines are trackers that haven’t been tracked.

The Live Camera Match option moves the camera as you reposition the tracker gizmos. The Sync Animation option causes the Time slider and the viewports to update along with the Movie Stepper buttons.

Caution	Be aware that updating the viewports with the Sync Animation option can slow down the
	system substantially.

The Error Threshold rollout, shown in Figure 25-7, lets you set the maximum allowable error values for Match Error, Variance Delta, and Jump Delta. Match Error measures the differences in the current frame to the best match. The Variance Delta is a measure of the difference in color between the target and the match, and the Jump Delta looks at the distance the tracker has moved in the current frame compared to the last five frames. If the tracking exceeds these values, an error appears in the Tracking Error Review list in the Batch Track rollout.

Automating the tracking process

After the parameters have been set up, you can use the Complete Tracking button in the Batch Track rollout, also shown in Figure 25-7, to start the tracking process. As tracking proceeds, any errors are captured and displayed in the Tracking Error Review list. After reviewing the errors, go to the Movie Stepper rollout to correct them, and run the tracking process again. This iterative process produces the best results.

672 Part V Cameras

Figure 25-7: The Error Threshold rollout lets you specify which errors to flag, and the Batch Track rollout lets you initialize tracking.

The Complete Tracking button initiates the tracking process. This process tracks only those frames that haven’t been tracked yet. The Check Status button checks for errors and for any frames that haven’t been tracked. Any errors are displayed in the Tracking Error Review list, and the tracks that haven’t been completed are displayed next to the Incomplete label.

Note Each error listed displays the tracker number, the frame number, an error code, and the threshold value. Possible error codes include “me” for match error, “vd” for color variance error, and “jd” for jump error.

The Next button moves to the next error in the list, and the Clear button removes an error from the list.

The Position Data rollout lets you clear, show, or export the tracking data for the selected tracker, the enabled trackers, or all trackers. The Show Data button opens the data in a text window, shown in Figure 25-8. You can save exported data as an Excel spreadsheet in the .CSV format or as text with the .DAT extension.

Figure 25-8: The Show Data button in the Position Data rollout displays the tracking data in a text window.

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Matching the camera

After all the tracking positions have been established, you need to select a camera to match the tracking data. In the Match Move rollout, shown in Figure 25-9, is a Camera button (initially labeled “none”). Click this button to select the camera to use.

Note	The camera specified in the Match Move rollout must be a Free camera.

While matching the camera, you can specify which camera parameters to include in the process. Options include FOV, Pan, Truck H (horizontal), Dolly, Roll, Tilt, and Truck V (vertical). You can also specify the Movie Start and Animation Start frames, as well as the Frame Count. The Reset Ranges button resets the Movie Start, Animation Start, and Frame Count values to their defaults.

Figure 25-9: The Match Move and Move Smoothing rollouts let you select a camera to match to the tracking data and smooth the camera’s motion.

The Animate Displays option updates the viewport frame by frame with the camera match. The Generate Keyframes option creates keys for each frame of the match. When you’re all ready, the Match Move button starts the Match Move process. The Maximum Pixel Error displays the tracking error for each frame. To view all the error values in a text window, click the Show Errors button.

Smoothing the camera motion

After the camera is matched to the tracking data, its motion might be a little erratic and bumpy. You can smooth its motion using the Move Smoothing rollout, also shown in Figure 25-9. This rollout lets you select which options to include in the smoothing calculations: Rotation, Roll, Pan, Tilt, FOV, Position, Truck H (horizontal), Truck V (vertical), or Dolly.

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The two smooth types that you can choose from are Straight Line Average and Low Pass Filter with a Smooth Amount. You can also smooth just the Match Move Range or All Frames. With the options set, click the Smooth button to initiate the smoothing calculations.

Pinning objects

After the tracked data is captured, you can select an object to follow the path that is positioned in front of the camera. This technique is called pinning. In the Object Pinning rollout, shown in Figure 25-10, select a tracker from the drop-down list and click the Object to Pin button. Then select the object to pin in the viewport. You can also set a Pin Range, the Pin Space (Screen or Grid), and Pin Mode (Absolute or Relative). To complete the pinning, click the Pin button.

Figure 25-10: Use the Object Pinning rollout to position an object in front of the camera path.

Tutorial: Tracking a camera zooming past traffic cones

For this example, I’ve animated a camera that zooms over and past a series of orange traffic cones. The scene includes some trees that will be useful in establishing tracking points.

To track a camera that is zooming past some traffic cones, follow these steps.

1.Open the Tracking past cones.max file from the Chap 25 directory on the CD-ROM. This file includes the same objects used to create the animation, but the camera and its path have been deleted.

2.Open the Utilities panel and click the More button. Then select the Camera Tracker utility and click OK.

3.In the Movie rollout, click the Movie file button and select the Camera past cones.avi file from the Chap 25 directory on the CD-ROM. The movie file appears.

4.Move the movie display out of the way and select Create Helpers Camera Point. Name the camera point object cone 01 and position it at the top-left corner of the cone in the Front viewport. Create, name, and position similar camera points for all six cones and the three trees.

5.Select the Utilities panel and, in the Motion Trackers rollout, click the New Tracker button. A Tracker gizmo appears in the movie display labeled 1. Click the Scene Object button, press the H key to open the Select Objects dialog box, and select the matching camera point for cone 01. Drag the gizmo and center it on the top-left corner of the first

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cone. Move through the movie’s frames in the Movie Stepper rollout and for each frame drag the tracker gizmo to the cone’s new location. When the cone leaves the scene at frame 3, click the Set Stop button in the Motion Trackers rollout.

6.Repeat step 4 to create additional trackers for the remaining cones and the trees. If the point you’re tracking is obscured or goes off the screen, skip that frame.

7.Once the gizmos have been positioned for all relevant frames, click the Complete Tracking button in the Batch Track rollout. When the tracking process completes, press the Check Status button and note the listed Incompletes. Return to the trackers for the frames marked incomplete and add some tracking points. Continue this step until the Check Status button returns a None for the Incompletes.

8.Select Create Cameras Free Camera and click in the Top viewport to create a camera. In the Match Move rollout in the Utilities panel, click the Camera button and select the scene camera in the Top viewport. Then click the Match Move button. If any errors appear, note the frame number and click Ok to continue. After Match Move is complete, you can go back and fix the frames that gave you errors.

9.Select the Perspective viewport and press the C key to change it to the camera view. Then, press the Play button (/) to see the final camera tracking.

Figure 25-11 shows scene after camera tracking has been completed. Notice that the keys are positioned along the Track Bar except for the end of the animation, where tracking produced some errors.

Figure 25-11: Be sure the scene includes several unique trackable objects before trying to track a camera.