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Planar tracking is a tool, and a powerful one at that, so it offers a lot of ways to hit your thumb with this hammer, so to speak. As always, your best defense is for you to take the time to understand what the various features do, and think carefully about how they apply to the details of your shot. Make sure there is enough information available for your task to be done, even in theory! And make sure you are using the right tool.
Some planar tracking limitations are in your control, and require that you set various parameters appropriately, for example the size of the search area, so we'll
discuss that in sections below. Other limitations revolve around things that destroy the imagery being tracked, such as occluding objects; we'll discuss those below too.
More significantly, users should be aware that though 3D planar tracking is a quick way to get some approximate 3-D, it is not a substitute for a full 3-D track of the scene. It offers nowhere near the accuracy of a 3-D solve: as you'll see working with 3- D planar trackers, small changes in corner position results in large changes in 3-D position, orientation, and field of view. That is telling you directly that a 3-D plane is sensitive to noise. And the smaller the plane appears in the camera image, the proportionately larger the noise is!
Observation : a 3-D solve calculates the FOV from tens or hundreds of trackers spread across the many frames of the entire shot. A 3-D planar tracker's FOV is based on four manually-placed locations in a single frame. The 3-D planar tracker has exactly the minimum information required, while a 3-D solve has much, much more, and that redundant data is averaged to produce a more-accurate value.
Each planar tracker specifies a field of view for each and every frame. When you have multiple planar trackers, this poses a bit of a problem, since the camera can have only one field of view on a given frame (and usually, it's the same for the entire shot).
So the interaction between 3-D planar trackers requires some care, see Adding More 3- D Planar Trackers.
Similarly, if you have two planar trackers on the same wall, there's no assurance they will have exactly the same orientation, or the proper distances to be mutually coplanar. That gets even trickier.
You can easily envision all kinds of complicated ways to start tying multiple 3-D planar trackers together, to get them all aligned with respect to one another and the world. As soon as you start thinking about these considerations too much, STOP . This is your sign that you need to be doing a 3-D solve (potentially using your planar trackers as input).
If you find yourself especially concerned about the details of which way your plane is facing (the pyramid is pointing) so that you can add 3-D effects that are well off the 3-D plane, STOP . Again, this is a sign that you should be doing a 3-D solve.
Planar trackers don't intrinsically accommodate lens distortion in the source imagery. This is addressed below in the Advanced Topics section below.
If you find yourself playing around trying to get a planar solve to be accurate or handle some messy large occlusion problems, stop and think! The SynthEyes AUTO button can solve a lot of shots very quickly, using some of the roto masks you may have already set up! Be sure you are using the right tool for the job!!!
©2023 Boris FX, Inc. — UNOFFICIAL — Converted from original PDF.