The barycenter layout method splits the input graph into a set of fixed and free vertices. Fixed vertices are nailed to the corners of a strictly convex polygon, while free vertices are placed in the barycenter of their neighbours. The barycenter force accessible from the BarycenterForce property of the layout is resposible for attracting the vertices to thier barycenter.
In case there are no fixed vertices this will place all vertices at a single point, which is obviously not a good graph drawing. That is why the barycenter layout needs at least three fixed vertices.
The minimal amount of fixed vertices is specified by the MinFixedVerticesCount property. If the input graph does not have that many fixed vertices, the layout will automatically forefill this requirement. This is done by fixing the vertices with the smallest degree.
In this example the fixed vertices are highlighted in orange.
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