diff --git a/editor.go b/editor.go
index 0c0442f..c273785 100644
--- a/editor.go
+++ b/editor.go
@@ -324,18 +324,13 @@ func passThroughImpl(pp *pc.PointCloud, core func(_, _ *pc.PointCloud) int) (*pc
 }
 
 func (e *editor) merge(pp *pc.PointCloud) {
-	pcNew := &pc.PointCloud{
-		PointCloudHeader: e.pp.PointCloudHeader.Clone(),
-		Points:           e.pp.Points + pp.Points,
-		Data:             append(e.pp.Data[:e.pp.Stride()*e.pp.Points], pp.Data...),
-	}
-	pcNew.Width = pcNew.Points
-	pcNew.Height = 1
-
-	e.push(&replacePatch{
-		header: e.pp.PointCloudHeader.Clone(),
-		data:   e.pp.Data,
+	e.push(&appendPatch{
+		oldPoints: e.pp.Points,
+		oldWidth:  e.pp.Width,
+		oldHeight: e.pp.Height,
 	})
-	e.pp = pcNew
+	n := e.pp.Points + pp.Points
+	data := append(e.pp.Data[:e.pp.Stride()*e.pp.Points], pp.Data...)
+	e.pp = newCloudView(e.pp, n, n, 1, data)
 	runtime.GC()
 }
diff --git a/patch.go b/patch.go
index 7032a60..17d88e6 100644
--- a/patch.go
+++ b/patch.go
@@ -30,6 +30,19 @@ var (
 	errNoLabelField     = errors.New("point cloud has no label field")
 )
 
+// pcgol caches an unsafe float32 alias of Data keyed only by its base pointer,
+// so a change of the Data length must be delivered in a fresh PointCloud.
+func newCloudView(pp *pc.PointCloud, points, width, height int, data []byte) *pc.PointCloud {
+	out := &pc.PointCloud{
+		PointCloudHeader: pp.PointCloudHeader.Clone(),
+		Points:           points,
+		Data:             data,
+	}
+	out.Width = width
+	out.Height = height
+	return out
+}
+
 func fieldByteOffset(h *pc.PointCloudHeader, name string) (int, bool) {
 	offset := 0
 	for i, fn := range h.Fields {
@@ -76,6 +89,30 @@ func (p *labelPatch) payload() []byte {
 	return nil
 }
 
+type appendPatch struct {
+	oldPoints, oldWidth, oldHeight int
+}
+
+func (p *appendPatch) revert(pp *pc.PointCloud) (*pc.PointCloud, error) {
+	stride := pp.Stride()
+	if stride <= 0 || p.oldPoints < 0 || p.oldWidth < 0 || p.oldHeight < 0 ||
+		p.oldPoints > pp.Points || p.oldPoints > len(pp.Data)/stride {
+		return nil, errBrokenPatch
+	}
+	return newCloudView(pp, p.oldPoints, p.oldWidth, p.oldHeight, pp.Data[:p.oldPoints*stride]), nil
+}
+
+func (p *appendPatch) encodeHead(buf *bytes.Buffer) {
+	buf.WriteByte(patchTypeAppend)
+	writeUint32(buf, uint32(p.oldPoints))
+	writeUint32(buf, uint32(p.oldWidth))
+	writeUint32(buf, uint32(p.oldHeight))
+}
+
+func (p *appendPatch) payload() []byte {
+	return nil
+}
+
 type replacePatch struct {
 	header pc.PointCloudHeader
 	data   []byte
@@ -150,6 +187,16 @@ func decodePatch(b []byte) (patch, []byte, error) {
 			return nil, nil, r.err
 		}
 		return p, r.b, nil
+	case patchTypeAppend:
+		p := &appendPatch{
+			oldPoints: int(r.uint32()),
+			oldWidth:  int(r.uint32()),
+			oldHeight: int(r.uint32()),
+		}
+		if r.err != nil {
+			return nil, nil, r.err
+		}
+		return p, r.b, nil
 	case patchTypeReplace:
 		p := &replacePatch{}
 		p.header.Version = math.Float32frombits(r.uint32())
diff --git a/patch_test.go b/patch_test.go
index 42abd88..3b96125 100644
--- a/patch_test.go
+++ b/patch_test.go
@@ -73,6 +73,24 @@ func TestLabelPatchRevert(t *testing.T) {
 	assertCloudEqual(t, orig, out)
 }
 
+func TestAppendPatchRevert(t *testing.T) {
+	orig := makeTestCloud(t, 100, 10, 10)
+	pp := cloneCloud(orig)
+
+	p := &appendPatch{oldPoints: pp.Points, oldWidth: pp.Width, oldHeight: pp.Height}
+	added := makeTestCloud(t, 10, 10, 1)
+	pp.Data = append(pp.Data, added.Data...)
+	pp.Points += added.Points
+	pp.Width = pp.Points
+	pp.Height = 1
+
+	out, err := p.revert(pp)
+	if err != nil {
+		t.Fatal(err)
+	}
+	assertCloudEqual(t, orig, out)
+}
+
 func TestReplacePatchRevert(t *testing.T) {
 	orig := makeTestCloud(t, 100, 10, 10)
 	orig.Viewpoint = []float32{0, 0, 0, 1, 0, 0, 0}
@@ -97,6 +115,7 @@ func TestPatchEncodeDecodeRoundTrip(t *testing.T) {
 	orig.Viewpoint = []float32{1, 2, 3, 1, 0, 0, 0}
 	patches := []patch{
 		&labelPatch{indices: []uint32{1, 2, 42}, oldLabels: []uint32{7, 8, 9}},
+		&appendPatch{oldPoints: 90, oldWidth: 9, oldHeight: 10},
 		&replacePatch{header: orig.PointCloudHeader.Clone(), data: orig.Data},
 	}