comments

.gitignore

@@ -0,0 +1 @@
+*.gltf

convert.go

@@ -15,6 +15,7 @@ func Convert(stl STL, outFile string) {
 	normalBuf := make([]byte, 0)
 	positionBuf := make([]byte, 0)
 
+	// padding each buffer part
 	padding := func(buf []byte) []byte {
 		log.Println("padding: ", len(buf)%4)
 		for len(buf)%4 != 0 {
@@ -24,22 +25,23 @@ func Convert(stl STL, outFile string) {
 		return buf
 	}
 
-	// 写入顶点
+	// positions to byte
 	for i := range stl.TriangleNum {
 		t := stl.Triangles[i]
 		positionBuf = append(positionBuf, t.Position...)
 	}
 	positionBuf = padding(positionBuf)
 
-	// 写入法向量
+	// normals to byte
 	for i := range stl.TriangleNum {
 		t := stl.Triangles[i]
+		// each position, write 3 times
 		normalBuf = append(normalBuf, t.Normal...)
 		normalBuf = append(normalBuf, t.Normal...)
 		normalBuf = append(normalBuf, t.Normal...)
 	}
 	normalBuf = padding(normalBuf)
-	// 写入索引
+	// indices to byte
 	for i := range stl.TriangleNum * 3 {
 		buf := make([]byte, 4)
 		binary.LittleEndian.PutUint32(buf, uint32(i))
@@ -49,22 +51,24 @@ func Convert(stl STL, outFile string) {
 
 	log.Println(len(positionBuf), len(normalBuf), len(indexBuf))
 
+	// concat
 	allData := make([]byte, 0)
-	allData = append(allData, indexBuf...)
-	allData = append(allData, normalBuf...)
-	allData = append(allData, positionBuf...)
-
+	allData = append(allData, indexBuf...)    // Indices: 0
+	allData = append(allData, normalBuf...)   // attributes["NORMAL"] = 1
+	allData = append(allData, positionBuf...) // attributes["POSITION"] = 2
+	
 	base := base64.StdEncoding.EncodeToString(allData)
 
 	attributes := make(map[string]int, 0)
-	attributes["POSITION"] = 2
 	attributes["NORMAL"] = 1
+	attributes["POSITION"] = 2
 
 	gltf := GLTF{
 		Asset:   Asset{Version: "2.0"},
 		Scenes:  []Scene{{Nodes: []int{0}}},
 		Nodes:   []Node{{Mesh: 0}},
 		Meshes:  []Mesh{{Primitives: []Primitive{{Attributes: attributes, Indices: 0, Mode: 4}}}},
+		// ByteLength not length after base64
 		Buffers: []Buffer{{Uri: fmt.Sprintf("data:application/gltf-buffer;base64,%s", base), ByteLength: len(allData)}},
 		BufferViews: []BufferView{
 			// index
@@ -72,58 +76,58 @@ func Convert(stl STL, outFile string) {
 				Buffer:     0,
 				ByteOffset: 0,
 				ByteLength: len(indexBuf),
-				Target:     34963,
+				Target:     34963, // ELEMENT_ARRAY_BUFFER  float   indices
 			},
 			// normal
 			{
 				Buffer:     0,
 				ByteOffset: len(indexBuf),
 				ByteLength: len(normalBuf),
-				Target:     34962,
+				Target:     34962,  // ARRAY_BUFFER    int   vertex
 			},
 			// position
 			{
 				Buffer: 0,
-				// ByteOffset: len(indexBuf),
 				ByteOffset: len(indexBuf) + len(normalBuf),
 				ByteLength: len(positionBuf),
-				Target:     34962,
+				Target:     34962,  // ARRAY_BUFFER    int   vertex
 			},
 		},
 		Accessors: []Accessor{
 			{
 				BufferView:    0,
 				ByteOffset:    0,
-				ComponentType: 5125,
-				Type:          "SCALAR",
-				Count:         stl.TriangleNum * 3,
+				ComponentType: 5125,                // uint ;      5124 int will loss model parts  
+				Type:          "SCALAR",            // index
+				Count:         stl.TriangleNum * 3, // 1 index : 1 position
 			},
 			{
 				BufferView:    1,
 				ByteOffset:    0,
-				ComponentType: 5126,
+				ComponentType: 5126,                 // float
 				Type:          "VEC3",
-				Count:         stl.TriangleNum * 3,
-				Max:           []float32{1, 1, 1},
+				Count:         stl.TriangleNum * 3,  // 1 normal : 1 position
+				Max:           []float32{1, 1, 1},   // or cal from stl data
 				Min:           []float32{-1, -1, -1},
 			},
 			{
 				BufferView:    2,
 				ByteOffset:    0,
-				ComponentType: 5126,
+				ComponentType: 5126,                 // float
 				Type:          "VEC3",
-				Count:         len(positionBuf) / 12,
-				Max:           stl.Max,
+				Count:         len(positionBuf) / 12,// xyz = 4x3; or stl.TriangleNum * 3
+				Max:           stl.Max,              // cal from stl data
 				Min:           stl.Min,
 			},
 		},
 	}
-
+	// or not indent
 	data, err := json.MarshalIndent(gltf, " ", " ")
 	if err != nil {
 		log.Println("marshal error: ", err.Error())
 		return
 	}
+	// output
 	os.Remove(outFile)
 	f, err := os.OpenFile(outFile, os.O_CREATE, os.ModePerm)
 	if err != nil {

data.go

@@ -11,18 +11,17 @@ type Triangle struct {
 	XYZ []float32
 }
 
-func (t Triangle) EuqalsPosition(position []byte) bool {
-	x1 := binary.LittleEndian.Uint32(position[:4])
-	y1 := binary.LittleEndian.Uint32(position[4:8])
-	z1 := binary.LittleEndian.Uint32(position[8:12])
 
-	x2 := binary.LittleEndian.Uint32(t.Position[:4])
-	y2 := binary.LittleEndian.Uint32(t.Position[4:8])
-	z2 := binary.LittleEndian.Uint32(t.Position[8:12])
-
-	return x1 == x2 && y1 == y2 && z1 == z2
-}
+//
+//        header     num
+//   |----80B------|-4B-|-----triangle1--------|--------triangle2-------|-----------...
 
+//                    Normal(xyz) 4 x 3       position1       position2          position3         attribute
+//   each triangle: |--------12--------|--------12--------|--------12--------|--------12--------|---2-------|
+//  
+//
+//
+//
 type STL struct {
 	Header      string
 	TriangleNum int

load.go

@@ -12,8 +12,11 @@ func Load(filePath string) (stl STL) {
 	if err != nil {
 		log.Panic("open file " + filePath + " error: " + err.Error())
 	}
+
+	// load 80 header
 	headerBuf := make([]byte, 80)
 	file.Read(headerBuf)
+	// int32
 	triangleNumBuf := make([]byte, 4)
 	file.Read(triangleNumBuf)
 
@@ -30,7 +33,7 @@ func Load(filePath string) (stl STL) {
 
 		positionBuf := make([]byte, 4*3*3)
 		file.Read(positionBuf)
-
+		// find max/min xyz
 		for r := range 3 {
 			x := math.Float32frombits(binary.LittleEndian.Uint32(positionBuf[:4+(r*4)]))
 			y := math.Float32frombits(binary.LittleEndian.Uint32(positionBuf[(r * 4) : (r*4)+4]))