在Golang中读取二进制.fbx文件

Question

Unlike in other languages, I really couldn't figure out how to read a binary file into an array of bytes or just turn it into an ASCII-string, which puts me into quite a problem.

The code I've been using:

func TestFBX(fileName string) {
    file, err := os.Open(fileName)
    if (err != nil) {
        log.Fatal(err)
    }
    defer file.Close()

    var content []byte
    scanner := bufio.NewScanner(file)
    for scanner.Scan() {
        text := []byte(scanner.Text())
        buf := bytes.NewReader(text)
        err := binary.Read(buf, binary.LittleEndian, &content)

        if (err != nil) {
            fmt.Println(err)
        }
    }

    fmt.Printf("%v", content)
    fmt.Println("")

    if err := scanner.Err(); err != nil {
        log.Fatal(err)
    }
}

What it does in the end is print out [ ], an empty slice. Now when I tried putting float64 or int32 instead of []byte it did print out different numbers but I still honestly don't get how to read the whole file and not just whatever number is there at the beginning.

Answer 1

If you still interested in golang FBX reader here is my implementation https://github.com/o5h/fbx. Not well tested, but should work.

Internally FBX have following structure:

type Header [27]byte
type FBX struct {
  Header *Header
  Top    *Node
  Nodes  []*Node
}
type Node struct {
  EndOffset       uint32
  NumProperties   uint32
  PropertyListLen uint32
  NameLen         uint8
  Name            string
  Properties      []*Property
  NestedNodes     []*Node
 }
 type Property struct {
  TypeCode byte
  Data     interface{}
 }

Here is an usage example:

f, _ := os.Open("cube.fbx")
defer f.Close()
fbxData, _ := fbx.ReadFrom(f)
ibo := fbxData.Filter(fbx.FilterName("PolygonVertexIndex"))[0]
fmt.Println(ibo)

Output will be

[0 2 -4 7 5 -5 4 1 -1 5 2 -2 2 7 -4 0 7 -5 0 1 -3 7 6 -6 4 5 -2 5 6 -3 2 6 -8 0 3 -8]

Here is an example, how I get other attributes

ibo := node.FilterName("PolygonVertexIndex")[0].Properties[0].AsInt32Slice()
vbo := node.FilterName("Vertices")[0].Properties[0].AsFloat64Slice()
normals := node.FilterName("Normals")[0].Properties[0].AsFloat64Slice()
uvIndex := node.FilterName("UVIndex")[0].Properties[0].AsInt32Slice()
uv := node.FilterName("UV")[0].Properties[0].AsFloat64Slice()

numFaces := len(ibo) / 3
for f := 0; f < numFaces; f++ {
    face := &Face{}

    index := f * 3
    a := int(ibo[index+0])
    b := int(ibo[index+1])
    c := int(ibo[index+2])*-1 - 1

    face.a.Position = getVec3(vbo, a)
    face.b.Position = getVec3(vbo, b)
    face.c.Position = getVec3(vbo, c)

    uva := int(uvIndex[index+0])
    uvb := int(uvIndex[index+1])
    uvc := int(uvIndex[index+2])
    face.a.UV = getVec2(uv, uva)
    face.b.UV = getVec2(uv, uvb)
    face.c.UV = getVec2(uv, uvc)

    face.a.Normal = getVec3(normals, f*3+0)
    face.b.Normal = getVec3(normals, f*3+1)
    face.c.Normal = getVec3(normals, f*3+2)

    faces[f] = face
}

type Vec3 struct {
    X, Y, Z float32
}
type Vec2 struct {
    X, Y float32
}
type Vertex struct {
    Position *Vec3
    Normal   *Vec3
    Color    *Vec3
    UV       *Vec2
}

type Face struct {
    a vertex.Vertex
    b vertex.Vertex
    c vertex.Vertex
}

func getVec3(data []float64, index int) *Vec3 {
    i := index * 3
    x := float32(data[i])
    y := float32(data[i+1])
    z := float32(data[i+2])
    return &Vec3{x, y, z}
}