What is outline on outline ?
You can see a white outline which seems to be an outline of another outline (color violet).
How to create it ?
This is not true outline on outline (and I think this is not technically possible)
1.You have to create a advanced outline (or outline).
2.Duplicate the first advanced outline and then select the advanced outline (which is below) and increase it’s width.
3.You also need to link the Width Point List and Vertex List of both outline to each other (with valueNodes).
(If you also want the width of outline of outline to be relative to the parent outline you can link them and with using proper converter you can apply the logic for it to be relative to the parent outline)
And you get the effect.
Here is the file for animation above: outline outline.sif (25.2 KB)
(If anyone know any better way let me know)