go.mobile/example/gopher: parse wavefront obj file
LGTM=nigeltao R=nigeltao, adg CC=davidday, golang-codereviews https://golang.org/cl/139510043
This commit is contained in:
David Crawshaw
parent
79cb3f5193
commit
400bc443a2
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@ -0,0 +1,335 @@
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// Copyright 2014 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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//+build ignore
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// Gengopher processes a simplified wavefront object file into a set of triangles.
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//
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// Usage:
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// go run gengopher.go -output gopher.go -input gopher.obj
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//
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// Normally used via go:generate.
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package main
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import (
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"bufio"
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"bytes"
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"compress/flate"
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"encoding/binary"
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"flag"
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"fmt"
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"go/format"
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"io"
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"log"
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"os"
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"strconv"
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"strings"
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)
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var (
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output = flag.String("output", "gopher.go", "output file name")
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input = flag.String("input", "gopher.obj", "input file name")
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)
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type vector struct {
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x, y, z float32
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}
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type face struct {
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// index values into the vertices, textures, and normals slices.
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v [3]int // index into vertices
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t [3]int // index into textures (not implemented)
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n [3]int // index into normals
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}
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type obj struct {
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name string
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faces []face
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}
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var vertices []vector
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var normals []vector
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var objs []obj
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func main() {
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flag.Parse()
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if err := parseAndWrite(); err != nil {
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fmt.Fprintf(os.Stderr, "%s\n", err)
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os.Exit(2)
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}
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}
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func parseAndWrite() (err error) {
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out, err := os.Create(*output)
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if err != nil {
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return err
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}
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defer func() {
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outerr := out.Close()
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if err == nil {
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err = outerr
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}
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}()
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in, err := os.Open(*input)
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if err != nil {
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return err
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}
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defer in.Close()
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if err := parse(in); err != nil {
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return err
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}
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buf := new(bytes.Buffer)
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writeObjs(buf, objs)
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b, err := format.Source(buf.Bytes())
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if err != nil {
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os.Stdout.Write(buf.Bytes()) // useful for debugging
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return err
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}
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_, err = out.Write(b)
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return err
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}
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func writeObjs(w io.Writer, objs []obj) {
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fmt.Fprint(w, preamble)
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for _, obj := range objs {
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log.Printf("writing %s", obj.name)
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vdata, ndata := obj.triangleBytes()
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fmt.Fprintf(w, "var %s = []byte{", obj.name)
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writeBytes(w, vdata)
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fmt.Fprintf(w, "\n}\n\n")
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fmt.Fprintf(w, "var %sNormals = []byte{", obj.name)
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writeBytes(w, ndata)
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fmt.Fprintf(w, "\n}\n\n")
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}
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}
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func writeBytes(w io.Writer, data []byte) {
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for i, b := range data {
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if i%12 == 0 {
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fmt.Fprintf(w, "\n\t")
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}
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fmt.Fprintf(w, "0x%02x, ", b)
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}
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}
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var preamble = `// Copyright 2014 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Generated by gengopher.go, do not edit manually.
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// Original data data has the copyright:
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//
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// The Go gopher was designed by Renee French. (http://reneefrench.blogspot.com/)
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// The gopher 3D model was made by Takuya Ueda (http://u.hinoichi.net).
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// Licensed under the Creative Commons 3.0 Attributions license.
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//
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// Model from http://github.com/golang-samples/gopher-3d
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// Each variable contains gzipped 3-component float32 triangle data.
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package main
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`
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func (obj obj) triangleBytes() (vdata, ndata []byte) {
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var v, n []float32
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for _, f := range obj.faces {
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l := len(vertices)
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if f.v[0] > l || f.v[1] > l || f.v[2] > l {
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log.Printf("bad face %v, len(vertices)=%d", f, l)
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continue
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}
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for _, ind := range f.v {
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val := vertices[ind]
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v = append(v, val.x, val.y, val.z)
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}
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if f.n[0] >= 0 {
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for _, ind := range f.n {
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val := normals[ind]
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n = append(n, val.x, val.y, val.z)
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}
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}
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}
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var dn []byte
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if len(n) > 0 {
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dn = deflate(n)
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}
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return deflate(v), dn
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}
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func deflate(v []float32) []byte {
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buf := new(bytes.Buffer)
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w, err := flate.NewWriter(buf, 9)
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if err != nil {
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log.Fatal(err)
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}
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if err := binary.Write(w, binary.LittleEndian, v); err != nil {
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log.Fatal(err)
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}
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if err := w.Close(); err != nil {
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log.Fatal(err)
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}
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return buf.Bytes()
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}
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func parse(r io.Reader) (err error) {
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line := 0
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defer func() {
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if err != nil {
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err = fmt.Errorf("%d: %v", line, err)
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}
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}()
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o := obj{}
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done := func() {
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if o.name == "" {
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return
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}
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objs = append(objs, o)
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fmt.Fprintf(os.Stderr, "%5d faces: %s\n", len(o.faces), o.name)
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o = obj{}
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}
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scanner := bufio.NewScanner(r)
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for scanner.Scan() {
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line++
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b := scanner.Bytes()
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if len(b) == 0 {
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continue
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}
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switch {
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case b[0] == '#':
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// comment, ignore
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case b[0] == 's', b[0] == 'l':
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// TODO(crawshaw): what is this?
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case b[0] == 'o':
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done()
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o.name = strings.Replace(string(b[2:]), ".", "_", -1)
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case b[0] == 'f':
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f, err := parseFace(b[2:])
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if err != nil {
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return err
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}
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o.faces = append(o.faces, f)
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case b[0] == 'v':
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switch b[1] {
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case ' ':
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v, err := parseVector(b[2:])
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if err != nil {
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return err
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}
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vertices = append(vertices, v)
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case 't':
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return fmt.Errorf("vt not supported")
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case 'n':
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v, err := parseVector(b[3:])
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if err != nil {
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return err
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}
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normals = append(normals, v)
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case 'p':
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return fmt.Errorf("vp not supported")
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}
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case bytes.HasPrefix(b, []byte("mtllib")):
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// ignore
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case bytes.HasPrefix(b, []byte("usemtl")):
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// ignore
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default:
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return fmt.Errorf("unknown wavefront prefix: %q", b[0])
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}
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}
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done()
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return scanner.Err()
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}
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func parseVector(line []byte) (vector, error) {
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var v vector
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i := bytes.IndexRune(line, ' ')
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if i == -1 {
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return v, fmt.Errorf("expected three vector values, found one")
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}
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x, err := strconv.ParseFloat(string(line[:i]), 32)
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if err != nil {
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return v, fmt.Errorf("vector x: %s", err)
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}
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v.x = float32(x)
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line = line[i+1:]
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i = bytes.IndexRune(line, ' ')
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if i == -1 {
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return v, fmt.Errorf("expected three vector values, found two")
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}
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y, err := strconv.ParseFloat(string(line[:i]), 32)
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if err != nil {
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return v, fmt.Errorf("vector y: %s", err)
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}
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v.y = float32(y)
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line = line[i+1:]
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i = bytes.IndexRune(line, ' ')
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if i != -1 {
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return v, fmt.Errorf("expected three vector values, found more")
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}
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z, err := strconv.ParseFloat(string(line), 32)
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if err != nil {
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return v, fmt.Errorf("vector z: %s", err)
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}
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v.z = float32(z)
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return v, nil
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}
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func parseFace(line []byte) (face, error) {
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var f face
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pos := 0
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for i := 0; i < 3; i++ {
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pos = bytes.IndexRune(line, ' ')
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if i < 2 && pos == -1 {
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return f, fmt.Errorf("expected three face values, found %d", i)
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} else if i == 2 {
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if pos != -1 {
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return f, fmt.Errorf("expected three face values, found more")
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}
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pos = len(line)
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}
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var vals []int
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for _, m := range bytes.Split(line[:pos], []byte{'/'}) {
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if len(m) == 0 {
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vals = append(vals, -1)
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continue
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}
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v, err := strconv.ParseInt(string(m), 10, 32)
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if err != nil {
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return f, fmt.Errorf("face[%d]: %s", i, err)
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}
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// wavefront faces are 1-indexed.
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vals = append(vals, int(v)-1)
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}
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f.v[i] = vals[0]
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f.t[i] = vals[1]
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f.n[i] = vals[2]
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line = line[pos:]
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if len(line) > 0 && line[0] == ' ' {
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line = line[1:] // remove space
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}
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}
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return f, nil
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}
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