Stykz can import and convert Pivot 2 and Pivot 3 .stk files by choosing File > Import Pivot .stk File. However there are some things that Pivot supports that Stykz doesn't, or that Stykz does, but just does it differently. This topic covers those compatibility issues.
Pivot 3 Beta allowed for you to attach a sprite (bitmap) as the first segment of a stick figure. Stykz does not support that yet, so if you import a Pivot 3 .stk file that contains a sprite, it will be ignored and the first non-sprite segment will be the first segment of the imported figure.
Circles in .stk Figures
Since Pivot and Stykz have different means of managing and drawing circles, there are some figures that were created in Pivot that don't translate completely into Stykz. If you import a .stk that falls into this category, you will get an alert dialog like this:
If you click "Explain", you will see this explanation:
Pivot supports the concept of hiding segments by changing their width to zero. Since Stykz does not support a width less than 1, Pivot .stk figures that have zero-width segments will actually import at a width of 7 pixels, but the Hidden attribute is automatically assigned to the segment so it remains hidden.
(Why 7 pixels? One of the frustrations that was heard from Pivot users was that once they had set a segment to be zero to hide it, when the time came to adjust it for some reason they had trouble selecting it, because to do so required locating the node that was at one end of the hidden line - which in a medium-to-complex figure could be hard to distinguish from other nodes bunched together in the same spot. So in Stykz, since hidden lines are actually displayed partially transparent when you have the Subselect tool active, 7 pixels was chosen to be large enough to see these "hidden" lines, so you could follow them to get to the appropriate node.)
Pivot also supports zero-length segments, but Stykz has a minimum length of 1. So any Pivot .stk figures that have a zero-length segment will be imported with a length of 1.
In Pivot, you could not actually fill a region with a color, so in order to simulate this, the common method was to make segments that were pretty thick, and go back and forth over the area to be "filled" until it looked like it was filled.
Stykz will import segments defined that way as originally created, but for performance and flexibility reasons, you should seriously consider changing your figure to take advantage of PolyFills, which let you define an area to fill with a color and it just does it... no segments required!
Experienced users of Pivot would use "transparency" .stks that were designed to make figures appear partially transparent when exported to GIF because of the way Pivot created the GIF animations. These .stk files, while they will probably import, they will not display properly since Pivot uses a different method of drawing these figures than Stykz does, and as a result it won't give you the transparency you're looking for. So for this reason, transparency .stks are considerd not compatible with Stykz.
NOTE: Adding a means for creating semi-transparency in Stykz when outputting to GIF is on the agenda for a future version of Stykz (probably the next one, as a matter of fact).
Some of the changes to Pivot .stks mentioned above may require that you "tweak" your imported figures in Stykz to get them to look exactly like they did in Pivot, but Stykz should import most figures without having to require you to make any changes at all!