If the image you are warping or morphing is in motion, it will be necessary to animate each spline so it moves with the feature of interest. To animate a spline, set keyframes for its axes or vertices at various places in the clip. The motion between the keyframes is automatically interpolated. Alternately, use the Stabilizer to automate the process by tracking a reference point and connecting an axis or vertex to the resulting tracking data. Whichever method you choose, you can further control the shape of the spline by adding or removing vertices throughout the animation.
For example, if you are creating a warp, you can load the Input1 clip into the Stabilizer and track all of the source spline's vertices. With Enable Warping selected from the Link box, you can then manually edit the points of the destination splines along the course of the clip to create the desired warp.
Similarly, if you are creating a morph, you can track the vertices of both source splines on the Input1 clip, as well as the source splines on the Input2 clip. When you then link the splines together in the Distort schematic for source interpolation, the morph animation is already set. You can refine the morph by further animating the destination spline.
At any frame, you can control the shape of the spline by adding and removing vertices. If the feature you are tracking gets larger, for example, you can add vertices to adjust the shape of the spline. Similarly, you can remove vertices that are no longer needed. Make them inactive from one keyframe to the next using the Active button, or permanently delete them. See Manipulating Vertices and Tangents.