The Graph Editor

The Graph Editor displays a graphical representation of computed camera parameters as well as providing options to edit the results. Depending on the type of camera motion (hand-held, stabilized, motion-controlled) and the quality of the 2D tracks, it may be useful to smooth some or all of the computed camera parameters. Smoothing can be done by hand, or by using a post filter.

Switch to the Graph Editor by clicking on the Graph Editor tab at the bottom of the Track window.

In the Parameter Tree, you can select the parameter you want display. The corresponding curve is then shown in the graph display.

The available parameters are:

The Graph Display shows the curve representing the selected parameter value over time. The X-axis always represents the time in frames, and the Y-axis represents the parameter value.

For example, rotation is expressed in degrees, translation is in the units defined in the coordinate system, and the focal length is in millimeters.

Each curve is shown as a continuous line joining the points calculated for each frame. The color of a curve is determined by the parameter it represents. One or more parameters can be selected and displayed at a time by using Shift or Ctrl+right-click.

The points used to extrapolate a curve are displayed in the Graph Display and can be edited.

Click to close the Graph Editor.

To restore the view, select Window > Track Window.

To fit the graph to the viewport, select Graph > Fit or right-click in the Graph Editor and select Fit from the pop-up menu.

The Graph Editor Toolbox

The Graph Editor Toolbox is displayed when you open the Graph Editor.

This toolbox provides access to the MatchMover post-filtering options. As you move the pointer over the graph, the Graph Editor Toolbox displays information on the position of the cursor (time and position) and the key number and its value in read-only fields.

If you select a key, or multiple keys using a rubber band selector or pressing Shift while selecting more keys, the keys are listed and you can set their value by entering a number in the Value field and clicking on Set Value.

The filter options are displayed in the Graph Editor Toolbox. After you have edited a camera parameter, use the recompute function to recalculate the effects of editing on the other parameters. See Smoothing a curve using post filters.

Toggle the Graph Editor Toolbox display by selecting Graph > Graph Editor > Editor Toolbox or use the pop-up menu.

Toggling the display grid

To toggle the grid display in the Graph Editor:

1. Click in the Graph Display to select it.
2. Do one of the following:
   • Select Graph > Show Grid to display the grid.
   • Right-click in the Graph Editor or the Track Status View and select Show Grid from the pop-up menu.

A check mark appears beside the option indicating that the option is activated.

Locking the grid axes

To lock the X- or Y-axis of the grid, either:

• Select Graph > X Locked or Y-Locked.
• Right-click in the Graph Editor or the Track Status View and click X Locked or Y-Locked in the pop-up menu.

A check mark appears beside the option indicating that the option is activated.

Smoothing a curve using post filters

The Graph Editor allows you to modify curves and point values using post filters. MatchMover has four types of post filter.

• Spline - Replaces frame parameters with the values obtained from spline interpolation of the neighboring values. This is useful when one frame looks “jumpy” and neighboring frames are not. In this mode, you can change the tangent of the curve at a given point to create a smoother curve.
• Linear - Replaces frame parameters with the values obtained by creating a linear curve between the first and last selected frame.
• Smooth - Applies a smoothing filter to the computed values. This is useful to remove the small vibrations that can appear in the computed camera path even when the actual camera motion is smooth.

For example, if the original camera path computed by MatchMover is too jagged, as shown below, we will use the smoothing function to improve it.

A low-strength smoothing operation polishes the curve while keeping the general motion.

However, if the smoothing is too strong, it will erase details and flatten the curve. Smoothing has worsened the result and the smoothed path is further from the solution than the originally computed one was.

Each time you modify a curve, its name in the Project window and the Track window changes to italic font and its corresponding icon changes to yellow.

This indicates that the value has been modified and some recomputation may be needed.

To smooth a curve using a post filter:

1. Click the Graph Editor tab.
2. Select the parameters to edit it in the left pane of the Graph Editor. Its curve will then be displayed in the Graph Editor.
   • To select more than one parameter use Shift+click to add new items to a current selection.
   • Use Ctrl+click to remove parameters from a selection.
   TipIf you select more than one parameter in the left pane of the Graph Editor, several curves will be displayed in the graph area.
3. Do one of the following:
   • Select a frame range. A frame range is a set of frames. In some situations, you may find that you only need to edit a limited part of your sequence. In the graph area, press Shift+click and drag the mouse horizontally to include the frames you want to select.
   • Select a curve point by clicking on it. This will turn the point into a small red circle. If you are in the Spline mode, it will also activate the display of the curve tangents at this point.
   NoteIf a time range exists, the filter is applied only to the frames within the time range. Frames outside the time range are unaffected. If no time range exists, the whole of the current sequence is filtered.
4. Select the relevant filter from the Graph Editor Toolbox.
   • to convert a time range to spline.
   • to convert a time range to inear.l
   • to smooth a time range. Edit the number in the corresponding text field to define the strength of the smoothing.
   • You can also set this value in the Smoothing Strength text field by selecting Edit > Preferences > 3D Tracking.
   • Right-click in the Graph Editor and select Filter and then a post filter from the pop-up menu.

MatchMover applies the post filter to the selection.

Modifying a curve manually

For more controllable editing of a curve, you can edit points manually.

1. Place the pointer over the curve point you wish to edit. The pointer changes to .
2. Click the point. The point changes to a red label with a pencil indicating that it is selected.

   

3. Drag and drop the point to its new position.
   TipYou can do exactly the same using multiple points selection.
   NoteYou can show or hide the original curve by toggling the option Graph > Graph Editor > Show Ghost or right-clicking in the Graph Editor and click Show Ghost in the pop-up menu. A check mark appears beside the option indicating that the option is activated.

Editing tangents

You can also edit the tangents. By default, the two vectors are aligned and synchronized. If desired, you can desynchronize the two tangents and set them independently.

1. Run a Spline filter on a curve.
2. Select a point.
3. Place the pointer over a tangent of the point to edit.

   

4. Move the pointer up or down to set the tangent.

   

To edit tangents freely:

1. Do one of the following:
   • Select Graph > Free Tangents.
   • Right-click in the Graph Editor and click Free Tangents in the pop-up menu.

   A check mark appears beside the option indicating that the option is activated.

2. Run a spline filter on a curve.

   See Smoothing a curve using post filters.

3. Select a point.
4. Place the pointer over a tangent of the point to edit.
5. Move the pointer up or down to set the tangent.

   

   NoteThe Free Tangent mode causes discontinuities in the smoothness of a curve and should be used by advanced users only.

Adding keys to and deleting keys from the curve

To add a key to the curve, do one of the following:

• Select Graph > Graph Editor > Add Key.
• Right-click in the Graph Editor and select Add Key from the pop-up menu.

To delete a key from the curve, select it and do one of the following:

• Select Graph > Graph Editor > Delete Key.
• Right-click in the Graph Editor and select Delete Key from the pop-up menu.

Resetting the curve

To restore the curve to its initial state, do one of the following:

• Select Graph > Graph Editor > Reset Curve.
• Right-click in the Graph Editor and select Reset Curve from the pop-up menu.