--- a/cmd/octreediff/main.go	Mon Mar 11 13:42:27 2019 +0100
+++ b/cmd/octreediff/main.go	Mon Mar 11 14:00:49 2019 +0100
@@ -130,97 +130,6 @@
 	}
 }
 
-type point struct {
-	x float64
-	y float64
-}
-
-type pointMap map[point]float64
-
-func (pm pointMap) triangulate() (*octree.Triangulation, error) {
-	vertices := make([]octree.Vertex, len(pm))
-	var i int
-	for p, z := range pm {
-		vertices[i] = octree.Vertex{X: p.x, Y: p.y, Z: z}
-		i++
-	}
-	return octree.Triangulate(vertices)
-}
-
-func sliceWork(
-	vs []octree.Vertex,
-	dst pointMap,
-	fn func([]octree.Vertex, func([]octree.Vertex) []octree.Vertex),
-) {
-	n := runtime.NumCPU()
-
-	wg := new(sync.WaitGroup)
-
-	slices := make(chan []octree.Vertex)
-	out := make(chan []octree.Vertex)
-
-	pool := make(chan []octree.Vertex, n)
-
-	const pageSize = 2048
-
-	turn := func(p []octree.Vertex) []octree.Vertex {
-		if p != nil {
-			out <- p
-		}
-		select {
-		case p = <-pool:
-		default:
-			p = make([]octree.Vertex, 0, pageSize)
-		}
-		return p
-	}
-
-	for i := 0; i < n; i++ {
-		wg.Add(1)
-		go func() {
-			defer wg.Done()
-			for slice := range slices {
-				fn(slice, turn)
-			}
-		}()
-	}
-	done := make(chan struct{})
-	go func() {
-		defer close(done)
-		for s := range out {
-			for i := range s {
-				v := &s[i]
-				key := point{x: v.X, y: v.Y}
-				if z, found := dst[key]; found {
-					dst[key] = (z + v.Z) * 0.5
-				} else {
-					dst[key] = v.Z
-				}
-			}
-			select {
-			case pool <- s[:0:pageSize]:
-			default:
-			}
-		}
-	}()
-
-	size := len(vs)/n + 1
-	for len(vs) > 0 {
-		var l int
-		if len(vs) < size {
-			l = len(vs)
-		} else {
-			l = size
-		}
-		slices <- vs[:l]
-		vs = vs[l:]
-	}
-	close(slices)
-	wg.Wait()
-	close(out)
-	<-done
-}
-
 func process(bottleneck string, firstDate, secondDate time.Time) error {
 	start := time.Now()
 	defer func() { log.Printf("processing took %v\n", time.Since(start)) }()
@@ -310,53 +219,7 @@
 		log.Printf("loading took %v\n", now.Sub(start))
 		last := now
 
-		firstVs, secondVs := first.Vertices(), second.Vertices()
-
-		result := make(pointMap, len(firstVs)+len(secondVs))
-
-		sliceWork(
-			firstVs,
-			result,
-			func(
-				slice []octree.Vertex,
-				turn func([]octree.Vertex) []octree.Vertex,
-			) {
-				p := turn(nil)
-				for i := range slice {
-					v := &slice[i]
-					if z, found := second.Value(v.X, v.Y); found {
-						p = append(p, octree.Vertex{v.X, v.Y, v.Z - z})
-						if len(p) == cap(p) {
-							p = turn(p)
-						}
-					}
-				}
-				if len(p) > 0 {
-					turn(p)
-				}
-			})
-
-		sliceWork(
-			secondVs,
-			result,
-			func(
-				slice []octree.Vertex,
-				turn func([]octree.Vertex) []octree.Vertex,
-			) {
-				p := turn(nil)
-				for i := range slice {
-					v := &slice[i]
-					if z, found := first.Value(v.X, v.Y); found {
-						p = append(p, octree.Vertex{v.X, v.Y, z - v.Z})
-						if len(p) == cap(p) {
-							p = turn(p)
-						}
-					}
-				}
-				if len(p) > 0 {
-					turn(p)
-				}
-			})
+		result := first.Diff(second)
 
 		now = time.Now()
 		log.Printf("setting in took %v\n", now.Sub(last))
@@ -384,7 +247,7 @@
 		log.Printf("loading clipping polygon took %v\n", now.Sub(last))
 		last = now
 
-		tri, err := result.triangulate()
+		tri, err := result.Triangulate()
 		if err != nil {
 			return err
 		}