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— Radial & Tangential: Model and solve for both radial and tangential distortion. Tangential relates to misaligned elements in a lens.
— Division Quadratic: Provides a more accurate simulation of Quadratic radial lens curvature. This causes the low and high order distortion values to be solved for.
— Division Quartic: Provides a more accurate simulation of Quartic radial lens curvature. This causes the low and high order distortion values to be solved for.
— Lower Order Radial Distortion: This slider is available for all simulations. It determines the quadratic lens curvature.
— Higher Order Radial Distortion: This slider is available only for Quartic simulations. Determines the quartic lens curvature.
— Tangential Distortion X/Y: These sliders are available only for Tangential simulations. Determines skew distortion.
Track Filtering
The Camera Tracker can produce a large number of automatically generated tracks. Rather than spending a lot of time individually examining the quality of each track, it is useful to have some less time-intensive ways to filter out large swaths of potentially bad tracks. The following input sliders are useful for selecting large amounts of tracks based on certain quality metrics, and then a number of different possible operations can be made on them. For example, weaker tracks can selected
and deleted, yielding a stronger set of tracks to solve from. Each filter can be individually enabled or disabled.
Selects tracks that have a duration shorter than the slider’s value. Short tracks usually don’t get a chance to move very far and thus provide less perspective information to the solver than a longer track, yet both short and long tracks are weighted evenly in the solve process, making long tracks more valuable to the solver. Locators corresponding to shorter tracks are also less accurately positioned in 3D space than those corresponding to longer tracks. If the shot has a lot of long tracks, it can be helpful to delete the short tracks. For typical shots, using a value in the range of 5 to 10 is suggested. If there are not a lot of long tracks (e.g., the camera is quickly rotating, causing tracks to start and move off frame quickly), using a value closer to 3 is recommended.
Selects tracks that have an average track error greater than the slider’s value. When tracking, tracks are automatically terminated when their track error exceeds some threshold. This auto termination controls the maximum track error, while this slider controls the average track error. For example, tracks following the foliage in a tree tend to be inaccurate and sometimes may be detected by their high average error.
Selects tracks that have a solve error greater than the slider’s value. One of the easiest ways to increase the accuracy of a camera solve is to select the 20% of the tracks with the highest solve error and simply delete them (although this can sometimes make things worse).
Selects the tracks within the scene that meet the above Track Filtering values. Note that when this button is pressed, the tracks that satisfy the filter values are displayed in the Selected Tracks area of the Solve tab and are colored in the viewer. This button is useful when Auto Select Tracks While Dragging Sliders is turned off or if the selection, for example, was accidentally lost by mis-clicking in the viewer.
When this is ticked on, dragging the above sliders (Minimum Track Length, Maximum Track Error, Maximum Solve Error) will cause the corresponding tracks to be interactively selected in the viewer.
Tracks selected directly in the viewer with the mouse or selected via track filtering can have the following operations applied:
Delete | Will remove the tracks from the set. When there are bad tracks, the simplest and easiest option is to simply delete them. |
Trim Previous | Will cut the tracked frames from the current frame to the start of the track. Sometimes it can be more useful to trim a track than deleting it. For example, high quality long tracks that become inaccurate when the feature they are tracking starts to become occluded or when the tracked feature moves too close to the edge of the image. |
Trim Next | Will cut the tracked frames from the current frame to the end of the track. |
Rename | Will replace the current auto generated name with a new name. |
Set Color | Will allow for user assigned color of the tracking points. |
Export Flag | This controls whether the locators corresponding to the selected tracks will be exported in the point cloud. By default all locators flagged as exportable. |
Solve Weight | By default, all the tracks are used and equally weighted when solving for the camera’s motion path. The most common use of this option is to set a track’s weight to zero so it does not influence the camera’s motion path but is still has a reconstructed 3D locator. Setting a tracks’ weight to values other than 1.0 or 0.0 should only be done by advanced users. Onscreen display of track names and values are controlled by these functions: — None: Will clear/hide the selected tracks. — Toggle: Will swap the selected tracks and unselect sets. — All: Will select all tracks. — Show Names: Will display the track name, by default these are a number. — Show Frame Range: Will display the start and end frame of a track. — Show Solve Error: Will display the amount of solve error each selected track has. |