--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/cmd/octree2contour/loader.go	Wed Sep 19 13:26:30 2018 +0200
@@ -0,0 +1,139 @@
+package main
+
+import (
+	"bufio"
+	"encoding/binary"
+	"io"
+	"log"
+	"math"
+	"os"
+
+	"github.com/golang/snappy"
+)
+
+type octree struct {
+	epsg uint32
+
+	vertices  []vertex
+	triangles [][]int32
+	index     []int32
+
+	min vertex
+	max vertex
+}
+
+func (v *vertex) read(r io.Reader) error {
+	var buf [8]byte
+	b := buf[:]
+	if _, err := io.ReadFull(r, b); err != nil {
+		return nil
+	}
+	v.x = math.Float64frombits(binary.LittleEndian.Uint64(b))
+	if _, err := io.ReadFull(r, b); err != nil {
+		return nil
+	}
+	v.y = math.Float64frombits(binary.LittleEndian.Uint64(b))
+	if _, err := io.ReadFull(r, b); err != nil {
+		return nil
+	}
+	v.z = math.Float64frombits(binary.LittleEndian.Uint64(b))
+	return nil
+}
+
+type byteReader interface {
+	io.ByteReader
+	io.Reader
+}
+
+func loadOctreeReader(r byteReader) (*octree, error) {
+	tree := new(octree)
+
+	if err := binary.Read(r, binary.LittleEndian, &tree.epsg); err != nil {
+		return nil, err
+	}
+
+	if err := tree.min.read(r); err != nil {
+		return nil, err
+	}
+
+	if err := tree.max.read(r); err != nil {
+		return nil, err
+	}
+
+	var numVertices uint32
+	if err := binary.Read(r, binary.LittleEndian, &numVertices); err != nil {
+		return nil, err
+	}
+
+	log.Printf("vertices: %d\n", numVertices)
+
+	vertices := make([]vertex, numVertices)
+	tree.vertices = vertices
+
+	for i := range vertices {
+		if err := vertices[i].read(r); err != nil {
+			return nil, err
+		}
+	}
+
+	var numTriangles uint32
+	if err := binary.Read(r, binary.LittleEndian, &numTriangles); err != nil {
+		return nil, err
+	}
+
+	log.Printf("triangles: %d\n", numTriangles)
+
+	indices := make([]int32, 3*numTriangles)
+	triangles := make([][]int32, numTriangles)
+	tree.triangles = triangles
+
+	var last int32
+
+	for i := range triangles {
+		tri := indices[:3]
+		indices = indices[3:]
+		triangles[i] = tri
+		for j := range tri {
+			v, err := binary.ReadVarint(r)
+			if err != nil {
+				return nil, err
+			}
+			value := int32(v) + last
+			tri[j] = value
+			last = value
+		}
+	}
+
+	var numNodes uint32
+	if err := binary.Read(r, binary.LittleEndian, &numNodes); err != nil {
+		return nil, err
+	}
+
+	log.Printf("num nodes: %d\n", numNodes)
+
+	tree.index = make([]int32, numNodes)
+	entries := tree.index[1:]
+
+	last = 0
+	for i := range entries {
+		v, err := binary.ReadVarint(r)
+		if err != nil {
+			return nil, err
+		}
+		value := int32(v) + last
+		entries[i] = value
+		last = value
+	}
+
+	return tree, nil
+}
+
+func loadOctree(fname string) (*octree, error) {
+
+	f, err := os.Open(fname)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+	return loadOctreeReader(bufio.NewReader(snappy.NewReader(f)))
+}