Is there a way to mark which triangle edges are polygon edges?

[nmr8acme]

Some output polygon edges are interior to a tessellated polygon, and some are exterior to it (i.e. edges of the tessellated poly.) Is there any way to get this information out of libtess2?

E.g. if I tessellate a quad with triangles, two edges of each output triangle will be "exterior edges", and one edge of each output triangle will be an "interior edge."

I'd like to know which are which so I can draw tessellated polygon outlines in the same pass that I draw the fills. (I.e. via this technique: http://codeflow.org/entries/2012/aug/02/easy-wireframe-display-with-barycentric-coordinates/) So I need to know which edges not to draw for that to work.

[memononen]

Yes, it is possible. Take a look at connected polygons output option:
https://github.com/memononen/libtess2/blob/master/Include/tesselator.h#L68

--mikko

[nmr8acme]

Perfect! Thanks Mikko!