Camera Tracking in After Effects

For the next part of my compositing I wanted to have a go at creating a camera track- using After Effects as it was available for me to use. I found tutorials online, on how to doing a basic track in AE then bringing it out to Maya to incorporate it in.

With a footage layer selected I did the following; chose effect> perspective > 3D tracker.In the tracker panel and click the track camera button. The 3D Camera Tracker effect is then applied. The analysis and solving phases occur in the background, with status appearing as a banner on the footage and next to the Cancel button.

They solves the footage, giving little coloured X’s on the screen

Attaching content into the scene involving a camera

  1. With the effect selected, select the track point or multiple track points (defining a best-fit plane) to use as the attach point.
    1. Hover between three neighboring unselected track points that can define a plane, a semitransparent triangle appears between the points. A red target appears, showing the orientation of the plane in 3D space.
    2. Draw a marquee-selection box around multiple track points to select them.
  2. Right-click above the selection or target, and then choose the type of content to create. The following types can be created:
    • Text
    • Solid
    • Null layer for the center of the target
    • Text, solid, or null layer for each selected point
    • “Shadow catcher” layer (a solid that accepts shadows only) for the created content by using the Create Shadow Catcher command in the context menu. A shadow catcher adds a light to the scene, if none exists.
Moving the target to attach content to different location 

To move the target so that you can attach content to a different location, do the following:

  1. When above the center of the target, the “move” cursor appears for repositioning the target.
  2. Drag the center of the target to desired location.

Once at the intended location, you can attach content by using the commands in the context menu.

Note: If the size of the targets is too small or too large to see, you can resize them to help visualize the planes. The target size also controls the default size of text and solid layers created using the context menu commands.

Effect controls for the 3D camera tracker 

The effect has the following controls and settings:
Analyze/Cancel
Starts or stops the background analysis of the footage. During analysis, status appears as a banner on the footage and next to the Cancel button.
Shot Type
Specifies whether the footage was captured with a fixed horizontal angle of view, variable zoom, or a specific horizontal angle of view. Changing this setting requires a resolve.
Horizontal Angle of View
Specifies the horizontal angle of view the solver uses. Enabled only when Shot Type is set to Specify Angle of View.
Show Track Points
Identifies detected features as 3D points with perspective hinting (3D Solved) or 2D points captured by the feature track (2D Source).
Render Track Points
Controls if the track points are rendered as part of the effect.
Note: When the effect is selected, track points are always shown, even if Render Track Points is not selected. When enabled, the points are displayed into the image allowing them to be seen during preview.
Track Point Size
Changes the displayed size of the track points.
Create Camera
Creates the 3D camera. A camera is automatically added when you create a text, solid, or null layer from the context menu.
Advanced controls

Advanced controls for the 3D camera tracker effect:

  • Solve Method: Provides hints about the scene to help in solving the camera. Solve the camera by trying the following:
    • Auto Detect: Automatically detects the scene type.
    • Typical: Specifies the scene as that which are not purely rotational, or mostly flat.
    • Mostly Flat Scene: Specifies the scene as mostly flat, or planar.
    • Tripod Pan: Specifies the scene as purely rotational.
  • Method Used: When Solve Method is set to Auto Detect, this displays the actual solve method used.
  • Average Error: Displays the average distance (in pixels) between the original 2D source points and a reprojection of the 3D solved points onto the 2D plane of the source footage. If a track/solve was perfect, this error would be 0 and there would be no visible difference if you toggled between 2D Source and 3D Solved track points. You can use this value to tell if deleting points, changing the solve method, or making other changes is lowering this value, and thus improving the track.
  • Detailed Analysis: When checked, makes the next analysis phase do extra work to find elements to track. The resulting data (stored in the project as part of the effect) is much larger and slower with this option enabled.
  • Auto-delete Points Across Time: With the new Auto-delete Track Points Across Time option, when you delete track points in the Composition panel, corresponding track points (i.e., track points on the same feature/object) are deleted at other times on the layer. You don’t need to delete the track points frame by frame to improve the quality of the track. For example, you can delete track points on a person running through the scene, whose motion should not be considered for the determination of how the camera was moving in the shot.
  • Hide Warning Banner: Use when you don’t want to reanalyze footage even though there is a warning banner indicating that it be reanalyzed.

Ground plane and origin in 3D Camera Tracker effect 

You can define a ground plane (reference plane) and origin, for example, the (0,0,0) point of the coordinate system within the 3D Camera Tracker effect.

  1. Analyze the scene using the 3D Camera Tracker effect
  2. Select a set of tracking points. This action causes the bullseye target to appear, showing the plane defined by the selected tracking points.
  3. Optionally drag the target by its center to reposition it along the plane, and place the center is where you want the origin to be.
  4. Right-click (Windows) or Control-click (Mac OS) the target and choose Set Ground Plane And Origin.

This action does not have any visible result, but the reference plane and origin of the coordinate system are saved for this scene. Any items that you create from within this instance of the 3D Camera Tracker effect are created using this plane and origin.

Creating the track. (Vimeo, 2017)
Camera Track Plug in- Exporting the track to Maya
One of the biggest challenges, seemingly, would be exporting the camera track to Maya (or the 3D package as I keep hearing). After searching the internet, I found lots of guidance towards a plug in created by Ryan Gilmore.
The above tutorial goes through the steps of how to create a track from footage (as described above).
References
Vimeo. (2017). After Effects New Features – Set Origin on 3D Track. [online] Available at: https://vimeo.com/63168530 [Accessed 3 Jan. 2017].

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