Function LoopFromCell

s2/loop.go:92–105

LoopFromCell constructs a loop corresponding to the given cell. Note that the loop and cell *do not* contain exactly the same set of points, because Loop and Cell have slightly different definitions of point containment. For example, a Cell vertex is contained by all four neighboring Cells, but it

(c Cell)

// loop contains points on its boundary that actually belong to other cells
// (i.e., the covering will include a layer of neighboring cells).
func LoopFromCell(c Cell) *Loop {
	l := &Loop{
		vertices: []Point{
			c.Vertex(0),
			c.Vertex(1),
			c.Vertex(2),
			c.Vertex(3),
		},
		index: NewShapeIndex(),
	}

	l.initOriginAndBound()
	return l
}

// These two points are used for the special Empty and Full loops.
var (