Take into account vertex data for edge weight function?

[gdalle]

trafficstars

At the moment the edge weight function only considers edge data. In some settings one could want to compute an edge weight online based on vertex features

[bramtayl]

Sure, I could see that. Should we pass three arguments to the weight function, the meta data of the two vertices and the edge between them? That would cause a significant performance drop I think, because we have to look up the meta data of the two vertices for every edge.