Setting in point for tracking to start

I am trying to track a dog. The shot starts with its front together and after a while it separates its 2 front legs. I thought to track the outside of the front legs first the when the dog starts to separate its legs to make another layer to subtract the space between its legs. I don’t know how to start the tracking for this subtracting layer in the middle of the shot. I am very new to Mocha, so sorry if its a basic question.

Of course after I posted I found where to set the in point for the layer!

I’ll respond just for the sake of other people on the forum asking the same question:

You can do this in one of two ways:

  1. Set the in point for the layer. This is at the top of the the “Layer Properties” panel.
  2. Keyframe the spline off screen by setting the point you want the shape to appear and then moving back a frame and dragging the shape off the image.

The first method is the usual approach, as it’s the easiest one to manage.

The second approach can be useful if you are exporting shape data and don’t want to animate the opacity to turn of the splines that don’t respect Mocha’s in/out layer approach.