(A tennis ball seems to be an ideal object to track.) Therefore using small balls as markers seems like one option. Spheres regardless of how they are oriented display the same shape and reflect light the same way. To improve chances of tracking would it be better to have the tracker work on the contrast & shape within the marker instead of between a marker and the varying background? For example, would high contrast markers with patterns such as these help the tracker?ģ) Circle half white and half black, etc.Ĥ) Other, high contrast within the markerĥ) Multi-markers, 3 circles close together.Ħ) A black rectangle - similar in size to the feature window? - with a white circle inside.Ĥ) Balls as Markers. I don’t know how the Kinovea tracker works. ? 3M has technical information on its retro-reflective products.ģ) Markers with Patterns.
Kinovea fo dummies full#
The use of RRT with considerable ambient background light and especially in full sunlight may not be practical. Lighting is an issue, easiest to use in low ambient background light. To use RRT put the markers on the object and place light sources very close and alongside the camera lens.
Retro-reflective tape has the same glass beads that are used in the road signs to reflect the headlights of your car back to you. It reflects light back in the direction that the light arrived from. One marker candidate is retro-reflective tape. Did the upper arm rotate or did the muscle with tape lag the rapid upper arm internal shoulder rotation?Ģ) Retro-Reflective Tape or Paint. If applied to the body one issue is that the tape may not move with the bones due to muscles bouncing, etc. Contrasting tape placed in reference locations.
Kinovea fo dummies professional#
This thread could use some advice on marker options from those who have professional experience selecting markers for high speed video in biomechanical research.ġ) Tape. No internet search yet so there may be many markers that I’m not familiar with. I have just a little experience using markers for high speed film imaging and almost no experience for sports applications or tracking. Has anyone used very light weight & bright LED markers that would show up in sunlight illumination? A ring of tape could be used on an arm or leg so that turning does not lose sight. It showed high contrast and a changing rectangular shape. To serve I put black electrician's tape on my upper arm and hand. But I don't know of effective video techniques that are practical. Does the search window continue on its previous path after the object is lost?Įventually I would like to attach a marker to a point on my tennis racket and track a total path as has been done. I just tried it a few times and don't recall any settings such as the search window. It reacquired it again after several/many? frames as the ball passed in front of a dark green practice hitting wall. It tracked the ball for a short distance away from the racket until the contrast deteriorated and then lost it. I tried to track a tennis ball going away with Kinovea. Or do you mean artificial things that are added for tracking such as tape, LED lights, etc.? Or, it does not matter for the tracking problem? Please post your findings, experiments, which markers work best, etc.Īnyone to do a video showing how various markers perform ?ĭefinition: By "markers" do you mean the features inherently in a scene such as a ball or the edge of a baseball bat. A color and brightness contrast with background that is not present in the rest of the search window. Marker that takes about half the feature window. To sum it up (based on the theory, I haven't done extensive testing in real conditions yet) (background and other parts on the person should be clear of anything that look like the marker). It will look in the immediate surroundings, so having a target that does not resemble any other part of its vicinity is better to avoid mismatches. (triangle, rectangle, square: not so good) It is not invariant to rotation, so if rotating the marker changes its look, it will be harder to match. (marker should have a different brightness than its background. Contrasting area will make the matching easier. So it is a measure of how much the candidate look like the original. The automatic tracking in Kinovea works by computing the cross correlation coefficient between a candidate window and the feature window of the previous image.įor each possible position in the search window, we get a score, and the best score is the match (unless it is under a specific threshold in which case we assume the target was lost). I was asked by mail about markers and the tracking algorithm.
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