Line tracking program

This tab contains more advanced parameters for adjusting various line tracking things. To bring up this tab, you must be running the line_tracking program by selecting it in the Program menu, and then bringing up the Configure Dialog (click on the gear icon or select File➜Configure). Now select the Expert tab under Pixy Parameters.

Warning! These are “expert” parameters. Some are used for testing/debugging and furthermore may cause the line tracking algorithm to act strangely for some values. No smoke will pour out of your Pixy2 (that's good) but exercising a little caution is advised!

• Edge distance: This parameter adjusts the distance (in pixels) between the edge detector. Increasing this value will help detect edges that are less distinct (fuzzier), but increasing will affect the barcode detection and decoding – that is, it will increase the minimum barcode size.
• Line extraction distance: This parameter is used for testing/debugging and currently has no effect.
• Maximum line compare: This parameter can be thought of as maximum line velocity parameter for tracking lines between frames. For example, if a line moves from one side of the frame to the other side of the frame in one frame period (i.e. improbably large line velocity), it's probably not the same line, so this parameter is a sanity check for the tracking algorithm. Decreasing this value tells the algorithm to be more restrictive regarding the line velocity. Increasing the value tells the algorithm to be less restrictive regarding line velocity.
• Maximum merge distance: This parameter determines how far the line tracking algorithm searches for nearby lines that might form an intersection. If the lines you are trying to track are wider, you should increase this parameter until the intersections formed with the wider lines are accurately detected.
• Minimum line length: This tells the algorithm to throw out lines shorter than this parameter.
• Line filtering: Increasing this parameter leads to more filtering and can result in less false positive line detections, but with some added latency regarding when new lines are reported.
• Intersection filtering: Increasing this parameter leads to more filtering and can result in less false positive intersection detections, but with some added latency regarding when new intersections are reported.
• Barcode filtering: Increasing this parameter leads to more filtering and can result in less false positive barcode detections, but with some added latency regarding when new barcodes are reported.
• Default turn angle: This parameter sets the path the algorithm takes when encountering an intersection. The algorithm will pick the path that is closest to the specified angle. Turn angles are specified in degrees, with 0 being straight ahead, left being 90 and right being -90 (for example), although any valid angle value can be used. Valid angles are between -180 and 180. This parameter is usually set to 0, which essentially means “go straight at intersections (or pick the straightest path) unless I tell you otherwise.” Telling the algorithm otherwise is done through setNextTurn() in the API.
• Delayed turn: This parameter tells the algorithm to stop choosing paths at intersections automatically. It requires the client program to indicate the path with setNextTurn() in the API before the intersection goes out of frame. It's an extra expert option. It's included because sometimes you might not know which way to turn at the next intersection until you actually see the intersection (the number of branches and their angles, for example.) It's also useful? fun? to set it because PixyMon will dutifully label the intersections: “3-way intersection”, “4-way intersection”, etc. because it doesn't know which way to turn yet.
• Manual vector select: When the algorithm initializes, it needs to figure out which line should be the Vector, a.k.a. the line you want to follow. It will automatically choose the Vector based on some characteristics that it thinks are attractive, like a line that intersects the bottom of the frame and/or a line that is close to vertical. You can bypass this selection process by enabling this parameter. The algorithm will then set the Vector based on setVector() calls through the API.