Tracking of an object is often lost during the movement, or not accurate enough.
You can greatly improve the accuracy of the tracking by using a high-contrasted drawing that you stick to the wanted object.
We used the attached markers for our internal tests with spectacular results (you have here 3 different resolutions).
For example, you want to track the angle of the knee of a runner. Use 3 stickers: one on the side of the knee at the rotation point, one on the thigh and one on the ankle, and draw an angle based on these points. Your angle tracking should now be flawless
