What is matchmoving/3D tracking/camera tracking?
Matchmoving is the art of working out from an image sequence the position and characteristics of the camera that shot it. It uses the parallax of features tracked within the shot to ascertain this and just requires a sequence shot with a moving camera. Camera tracker is able to calculate and reveal the 3D positions of a number of feature points within the shot. Those camera and feature points can then be used for 3D, compositing and motion graphics work, to allow seamless integration into the source shot.
How does Camera tracker differ from a planar tracker (such as Mocha)?
While the underlying technology behind these two classes of tools is relatively similar, their abilities and features are very different. Planar tracking allows you to identify planes within the image, and to see the way in which they translate and deform across the image sequence. Camera tracker (and matchmoving as a whole) allows you to extract the position and characteristics of a camera from its sequence, as well as the 3D positions of features within the scene. This allows you to create visual effects and motion graphics within the context of the entire scene, as opposed to simply within the plane of a single element.
How does Camera tracker differ from a 2D tracker?
Rather than attempting to track a single 2D position, Camera tracker tracks many 2D positions across the entire image and then, from the relative parallax of these moving points, figures out the most likely animation position and focal length/film back ratio for the camera with which the scene was shot.
Where can I find out more about camera tracking and matchmoving?
We have put together a playlist of Camera tracker tutorial videos that explain the specifics of using Camera tracker.
Camera tracker also comes with a detailed manual, which is available once the plug-in has been installed.
Tim Dobbert has written an introduction to the essentials of matchmoving, entitled Matchmoving: The Invisible Art of Camera Tracking.
How do I export my Camera tracker-created camera and null data to my 3D package?
Camera tracker doesn’t support this functionality internally. However, since Camera tracker simply creates standard After Effects cameras, nulls and solids, there is a range of free and paid for scripts for After Effects, which provide this ability.
These include:
MODO
Fredrik Stenson's AfterFxIO: For an example of using this tool, check out James Darknell's Camera tracker to Modo video
Maxon Cinema 4D - AEtoC4D - For an example use of this tool, see Marc Leonard's Camera tracker tutorial on AETuts+
Autodesk Maya - AE3D Export, MoCon
Autodesk 3ds Max - AE3D Export
NewTek Lightwave - AE3D Export
Why does my exported data look different when reading it into my 3D package?
This is very dependent on the script in question, however the most common problems include:
The 3D package's world coordinate system differs to that of After Effects. After Effects is unusual in that it places its 3D system centre at the top left of the frame. Other errors may include left to right handed coordinate systems. Correcting for this is again, dependent on the script in question, but often the parenting Null object the Camera tracker creates can be used to assist. For example, to deal with a centre framed coordinate system, grab the Camera tracker-created null, set its position to be 0, 0, 0 and then unparent all created cameras/nulls/solids before doing your export.
Export script doesn’t carry all information. Many scripts may not bring across every piece of information. Amongst those, commonly ignored pieces of data include comp size, camera film back, etc. To correct for this, simply copy across the offending items.
How do I copy and paste position and rotation data from a Camera tracker- created null/solid to my own object?
The objects created by Camera tracker are done so within the relative world space of the parenting (first created) null. As a result, to use this data directly you need to switch the source null/solid to reference its position and rotation data in absolute, rather than relative space. Simply un-parent the source object from the scene null, and then copy/paste from the source null to your desired target object.
How do I create a text or shape layer at one of the Camera tracker feature marks?
As usual, track, solve, create scene and set ground plane. Create a null object at this location using the Camera tracker by selecting the feature and using the menu entry for 'Create Null'. Now, read the above question regarding copying and pasting position and rotation data, and un-parent the null object you just created. Now create a Text or Shape layer, set it to 3D and either copy/paste over the data from the null, or parent to it. You can then adjust the scale and orientation as required.
Why does Camera tracker intermittently stop tracking (often when I move After Effects to the background)?
Camera tracker has two main modes of operation when tracking. It can either 'render during analysis' or not. The first is meant for quality-checking during tracking, and short tracking only. It is susceptible to interrupting signals sometimes sent by After Effects when it is backgrounded, or when autosave kicks in. This will stop the tracking process.
If you intend to background After Effects whilst you're tracking, or you're not interested in watching as it tracks, switch off the 'Render During Analysis' checkbox before pressing the track button. As an added advantage, this will track faster than if 'Render During Analysis' is on.
Why do my Camera tracker-created objects ‘float’ over the background clip?
This is indicative of either a poor feature selection, or a poor track. See our Camera tracker training series for information on how to pull good tracks and pick good features.
How do I improve the quality of my track and solve?
Watch our Camera tracker training series for a walkthrough of using the tool, as well as tips and tricks for common use cases.
My shot camera rotates but doesn't move - how can I solve it using Camera tracker?
Such a camera move is known as a nodal pan (strictly, a nodal pan occurs when the rotation happens around the nodal point of the lens, but most normal pans are close enough to be modeled as such). Class 9 of our Camera tracker training series, deals with handling such camera moves:
The technique essentially involves switching the Tracking->Track Validation drop down to 'Rotating Camera' and the Solve->Camera Motion drop down to 'Rotation Only' and proceeding as normal.
My shot camera changes focal length (i.e. zooms) during my shot - how can I solve it using Camera tracker?
Switch the Solve->Focal Length Type drop down to either:
• 'Unknown Varying' if you have no idea of the focal lengths involved in the change.
• 'Approximate Varying' if you have a rough idea of the focal lengths involved and subsequently dial them in as an animation to the 'Focal Length' parameter.
• 'Known' if you know exactly the focal lengths and time frame involved and subsequently dial them in as an animation to the 'Focal Length' parameter.
How can I find out information about the camera with which my scene was shot?
Camera tracker works better the more information you give it, since this can reduce the number of variables in the equations it's solving. The solve twirly contains most of the parameters that can be locked down in such a manner. Figuring out this data requires a little detective work, with sources ranging from metadata stored in the files themselves through to logs from set. Figuring out the metadata depends on the camera in question - R3D for example provide a range of tools with which you can see the metadata recorded, and dSLR sourced mov metadata may be available from Quicktime Player's movie inspector panel.