Plot the triangles produced by earcut, or plot the polygon paths
using the same interface as earcut uses. This allows for easy
comparison and checking of what the results should be.
Usage
plot_ears(xy, idx, add = FALSE, ...)
plot_holes(xy, holes = 0, add = FALSE, ...)
Arguments
xy
xy-coordinates, either a list, matrix, or data frame
For both functions the first input is
a matrix of x,y coordinates.
For plot_ears the second input is
the index output of earcut. The index is treated in sets of 3 values, with
individual calls to polypath to draw a polygon for each triangle.
For plot_holes the second input is the holes argument that would
be used for earcut. This is used to split the coordinates at these positions,
inserting NA values as per the mechanism used by graphics::polypath to
break coordinates into separate polygon rings. (There's no winding rule here
plot_rules is hard-coded to always use the evenodd rule, so that winding
order may be ignored).