Apply loop region patch

s2/loop.go

@@ -93,6 +93,16 @@ func LoopFromCell(c Cell) *Loop {
 	return l
 }
 
+// LoopFromDegrees constructs a loop from the given lat/lng degree pairs.
+func LoopFromDegrees(degs ...[]float64) *Loop {
+	pts := make([]Point, len(degs))
+	for i, d := range degs {
+		ll := LatLngFromDegrees(d[0], d[1])
+		pts[i] = PointFromLatLng(ll)
+	}
+	return LoopFromPoints(pts)
+}
+
 // EmptyLoop returns a special "empty" loop.
 func EmptyLoop() *Loop {
 	return LoopFromPoints([]Point{{r3.Vector{X: 0, Y: 0, Z: 1}}})
@@ -259,6 +269,35 @@ func (l Loop) CapBound() Cap {
 	return l.bound.CapBound()
 }
 
+// ContainsCell checks whether the cell is completely enclosed by this loop.
+// Does not count for loop interior and uses raycasting.
+func (l Loop) ContainsCell(c Cell) bool {
+	for i := 0; i < 4; i++ {
+		v := c.Vertex(i)
+		if !l.ContainsPoint(v) {
+			return false
+		}
+	}
+	return true
+}
+
+// IntersectsCell checks if any edge of the cell intersects the loop or if the cell is contained.
+// Does not count for loop interior and uses raycasting.
+func (l Loop) IntersectsCell(c Cell) bool {
+	for i := 0; i < 4; i++ {
+		crosser := NewChainEdgeCrosser(c.Vertex(i), c.Vertex((i+1)%4), l.Vertex(0))
+		for _, v := range l.Vertices()[1:] {
+			if crosser.EdgeOrVertexChainCrossing(v) {
+				return true
+			}
+		}
+		if crosser.EdgeOrVertexChainCrossing(l.Vertex(0)) { //close the loop
+			return true
+		}
+	}
+	return l.ContainsCell(c)
+}
+
 // Vertex returns the vertex for the given index. For convenience, the vertex indices
 // wrap automatically for methods that do index math such as Edge.
 // i.e., Vertex(NumEdges() + n) is the same as Vertex(n).