About the Pencil Line to Pencil Line Rule
If you trace a shape using a pencil line such as the Ellipse , Rectangle , Polyline , Line or Pencil tool, you have to morph it with another pencil line. Make sure that both drawings are pencil shapes (central vector).
A pencil line will never morph with a brush stroke.
Pencil lines with thickness are supported in morphing sequences. The thickness will morph according to the thickest and thinnest areas in the source and destination drawings.
Pencil lines with textures are not supported in a morphing sequence. During the morphing, the texture will disappear and show without pencil line opacity texture.
If you have pencil lines in your source drawing, the same number of pencil lines must be present in the destination drawings. A pencil line will appear if it is not found in the destination drawing. It will pop out on the first or last frame depending on which one it is drawn.
When two pencil lines cross one another, they are considered to be two lines and not four lines anymore (as it was in version 7.8 and below of the application). In this case, you must have two pencil lines in your destination drawing for your morphing to work correctly.