1

I am very new to this so forgive me if this is a stupid question!
There is a video that I saw here where the angle tool follows the original points of reference on the hip, knee and ankle.  I  can get it to follow for just a very short time; then the angle tool seems to lose all reference of the original reference points. What am I doing wrong?
Thanks....

2

Assuming you are using 0.8.27.

There are two main things that will impact tracking "stickiness": the size of the search boxes and the use of markers.

When you use the regular track tool by right clicking an object and doing Track Path, you'll see the two tracking boxes. These can be resized from the track tool configuration dialog. You want the inner box to be tight around the object you are tracking so it doesn't pick background. The outer box is the search region, size this one based on the speed of motion or framerate, that is how much displacement the object can undergo in one frame.

The tracking on other tools like angle also uses these boxes but they are hidden. You can configure them from Preferences > Drawing > Tracking. So what you can do is use a normal track tool to figure out appropriate box sizes and then use that here.

Using markers will greatly improve precision and reduce loosing the tracking. It's pretty much mandatory for tracking joint angles properly.