凸包
Wiki ▸ [[API Reference]] ▸ [[Geometry]] ▸ Hull Geom
# d3.geom.hull()
Create a new hull layout with the default x- and y-accessors.
# hull(vertices)
Returns the convex hull for the specified vertices array, using the current x- and y-coordinate accessors. The returned convex hull is represented as an array containing a subset of the input vertices, arranged in counterclockwise order (for consistency with polygon.clip).
Assumes the vertices array is greater than three in length. If vertices is of length <= 3, returns [].
# hull.x([x])
If x is specified, sets the x-coordinate accessor. If x is not specified, returns the current x-coordinate accessor, which defaults to:
function(d) { return d[0]; }
# hull.y([y])
If y is specified, sets the y-coordinate accessor. If y is not specified, returns the current y-coordinate accessor, which defaults to:
function(d) { return d[1]; }