func (l loopRegion) intersects(loop *s2.Loop) bool {
// Quick check if the bounding boxes intersect
if !l.RectBound().Intersects(loop.RectBound()) {
return false
}
// Quick check to see if the first vertex is in the loop.
if l.ContainsPoint(loop.Vertex(0)) {
return true
}
// At this stage the one vertex is outside the loop. We check if any of the edges of the cell
// cross the loop.
if l.edgesCrossPoints(loop.Vertices()) {
return true
}
// At this stage we know that there is one point of the loop is outside us and the boundaries do
// not interesect. The only way for the loops to intersect is if it contains us. We test this
// by checking if an arbitrary vertex is inside the loop.
if loop.RectBound().Contains(l.RectBound()) {
return loop.ContainsPoint(l.Vertex(0))
}
return false
}
// Intersects returns true if the two loops intersect.
func Intersects(l1 *s2.Loop, l2 *s2.Loop) bool {
if l2.NumEdges() > l1.NumEdges() {
// Use the larger loop for edge indexing.
return loopRegion{l2}.intersects(l1)
}
return loopRegion{l1}.intersects(l2)
}
func loopArea(l *s2.Loop) float64 {
n := l.NumEdges()
origin := l.Vertex(0)
var area float64
for i := 1; i < n-1; i++ {
area += s2.PointArea(origin, l.Vertex(i), l.Vertex(i+1)) * float64(s2.RobustSign(origin, l.Vertex(i), l.Vertex(i+1)))
}
return area
}