Hi Michael,
I know you are familiar with such, but as you ask in a forum, I like to have this more detailed than you personally need.
Simply said, this tracker is designed to find the camera movement, considering the context around it is stable.
It is practically only a mathematical relationship between object and camera. The tracker establishes the relationship between context and camera, by creating a camera animation path.
That we get the camera path as motion “plotted” out is more or less an default idea. The tracker algorithm has no clue if the camera moves or the context or both. This version here has the default of a stable context with a moving camera. So, we can take the camera on the first frame, create theoretically a static camera from this position, and use the motion camera as Parent for the complete scene. Theoretically, as this needs some work and care.
The problem to object tracking has these problems with the C4D tracker in mind:
• find first if the camera itself is moving, and if—how…
• find enough 2D tracking points in space on that object (enough parallax, motion?)
• draw a mask for that object and exclude any other objects for that part
• find the axis of the object
• subtract the camera motion from the object motion
• separate any influence that this object might have, shadows and reflections
• is the object stable (surface/feature/tracker) and allows for 3D tracking, how stable they are to each other.
• perhaps only 2D tracking is wanted, but is the z value available (object to camera)
• it might be a pure manual tracking, based on the change of light
• do you have some survey data, to support the 3D solve
• consider that far away objects might not track well
• record noise free
• avoid sharpening in the camera
• if possible, use short shutter speeds to avoid motion blur
• have a decent depth of field
• zoom lenses and the use of them while shooting, zooming, will disable its usability. (Change of distortion would be one point, not the major one of course)
• Image stabilization (needs to be evaluated)
• rack focus—not a good idea
Not specifically for that, more typically tracking requirements:
• know your lens, don’t believe the mm that is given, measure it for the focus distance you like to use (still lenses breath, so they are not fixed!)
• find your sensor size, if, e.g., RED, find out if only parts of the sensor were use
• for this version, avoid lenses with distortion, un-distort might limit the precession
• check if your footage has rolling shutter, if so, stop tracking
• avoid diffusion filtration
• avoid lens-flare, keep it clean
• use when ever possible lose less compression or raw, 16 bit/c if possible
• if it is a small sensor size camera, or a cheap one (iPhone etc) is the sensor centered?)
Trackers/Features and their quality/requirements are a longer theme, and I did not even found all problems discussed in any training I had nor in books. I will record these soon, but it is too much to list here. Sorry.
I have excluded here the 3D solve step, as that might be the more tricky one. If the camera is locked off and has not a single vibration even, then it looks more possible.
The application in its 1.0 state has no options to do that. You have to get the camera motion as one path, and then the object motion as another. I guess here, as we have many combinations of object moves, camera not, camera does, etc and as well the worse or best case, the camera follows the object that no parallax can be gained from the object. Worse -as it is not possible to get anything from a 3D tracker then, but nice, as we can use the Camera Calibrator then, as it is kind of static.
There are two sources that handles object tracking, and as I have read both carefully, I can only suggest them as good source for object tracking:
• “The Art and Technique of Matchmoving, Solutions for the VFX Artist”, Erica Hornung [Focal Press]
• Partly as Tim focus predominately on camera tracking: “Matchmoving, The Invisible Art of Camera Tracking”, Tim Dobbert, second edition {Sybex]
The short answer, if you have Syntheyes, you should enjoy the comfort of a streamlined option to get the camera solved as well the object[s]. The Syntheses C4D Python Exporter is nice anyway. With some work and in ideal situations it might be possible with other apps, but tracking is based on precision, and each step in the “chain of event” adds up.
“Is there a way to automatically track moving objects…” The simple answer is: no.
I have not discussed here 2D object tracking, such as silhouette tracking, as that might be more an Ae or Mocha question. I had in mind and understood, that you ask about an 3D object that has motion on its own, with camera movement or with a static camera.
I hope that allows for some orientation.
All the best
Sassi
