ZCard will create a 3D object (Axis, TransformGeo, Card, Card3D) or a Tracker node for a given pixel based on an image's depth channel and the render camera. This will keep you out of the 3D space for simple tasks like attaching a roto to a certain pixel.

ZCard assumes that the object, that the sampled pixel belongs to, is static and the motion comes from the camera.

To use, simply attach the render and the camera the render was produced with:

Select the desired output and hit "Create"