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What is 3-D Planar Tracking?
A regular SynthEyes tracker tracks a point, a single point feature in the 3-D environment, whether it's a spot of paint on the floor, or the corner of a window.
SynthEyes follows that point feature as it moves around the image over the duration of the shot. You then solve the overall scene, with many trackers, to find the 3-D position of the points and the path of the camera in 3-D.
By contrast, a 3-D planar tracker follows a fairly large rectangular surface (the plane), as it moves around the image and 3-D environment. While mathematically a plane is infinite in extent, the rectangles in planar tracking have a fixed width and height: a window on the wall, a tile on the floor, the screen of a computer monitor. The rectangle must be mathematically precise, with opposite edges parallel to each other in 3-D, and adjacent edges perpendicular to each other in 3-D. When the rectangle is projected onto the camera image plane, of course the sides are no longer parallel or perpendicular; the angles can be quite different (even kite-like) depending on the relative orientation of the rectangle versus the camera.
That bring us to the important point: the 3-D position of the planar tracking rectangle versus the camera, the aspect ratio of the rectangle, and the field of view of the camera can all be determined from the corner locations on each single frame of the image (see limitations below). So tracking even a single planar tracker is enough to give you a 3-D camera or object path for adding simple 3-D effects!
In reality, you often won't be able to set up truly parallel/perpendicular rectangles in the source imager, but it isn't strictly necessary. You'll generally be able to get a reasonable and usable approximate solution; the planar tracking display and control panels help make that easier.
The planar tracking rectangle does not have to correspond to any trackable surface. Using the in-plane masking capabilities, the region(s) of the tracked pixels can be any shape or have holes or be in multiple pieces or somewhat larger than the pixels being tracked. The surrounding and supporting rectangle ties everything into 3D. The pixels being tracked should be coplanar, or close to it, however.
The planar rectangle will often be textured with an image or sequence with an alpha channel in a downstream application. Clever choice of the planar rectangle may
let you achieve additional effects, such as adding details in locations with no trackable features.
Tip : As with regular tracking, interlaced footage should be avoided due to the reduced vertical resolution. Also, if you use the Interlaced: Yes mode for the shot, performance will be reduced somewhat.
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