Explore implications of path/ring origin and bridge segments

[mdsumner]

There's a bit of this in the vignette. Had a conversation with a colleague and we'd both thought "hmm, which triangulations end up the same from which kinds of starting variants" - and agreed it's probably a crazy thought and a massive can of worms.

[mdsumner]

see discussion here on the bridge ambiguity Decido Earcut Hole Index Is First Vertex of Hole .

There was a "bridge" example that used to used to confuse me, it's not this but might trigger ideas when I come back to this:

x <- c(0, 0, 0.75, 1, 0.5, 0.8, 0.69,
       0.2, 0.5, 0.5, 0.3, 0.2,
       0.15, 0.23, 0.2)
y <- c(0, 1, 1, 0.8, 0.7, 0.6, 0,
       0.2, 0.2, 0.4, 0.6, 0.4,
       0.65, 0.65, 0.81)
d <- data.frame(x = x, y = y, group = rep(1:3, c(7, 5, 3)))[c(1:7, 1, 8:12, 8, 13:15, 13), ]

library(ggplot2)
ggplot(d) + geom_polygon(aes(x, y, group = group, colour = factor(group), fill = group))