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mesh.go
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mesh.go
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package perspectivefungo
import (
"bufio"
"bytes"
"fmt"
"math"
"strconv"
"strings"
)
func LoadOFFMesh(d Driver, id string, data []byte, smooth bool) error {
scanner := bufio.NewScanner(bytes.NewReader(data))
if !scanner.Scan() {
return fmt.Errorf("Failed to read .OFF header")
}
if err := scanner.Err(); err != nil {
return err
}
header := strings.Fields(scanner.Text())
if header[0] != "OFF" {
return fmt.Errorf("Invalid .OFF header")
}
vertexCount, err := strconv.Atoi(header[1])
if err != nil {
return err
}
faceCount, err := strconv.Atoi(header[2])
if err != nil {
return err
}
var (
count int32
vertices []float32
normals []float32
tempVertices [][]float32
tempNormals [][]float32
tempFaces [][3]int
)
addOffFace := func(ss ...string) error {
var face [3]int
var vs [3][]float32
for i := 0; i < 3; i++ {
f, err := strconv.Atoi(ss[i])
if err != nil {
return err
}
face[i] = f
vs[i] = tempVertices[face[i]]
vertices = append(vertices, vs[i]...)
count++
}
tempFaces = append(tempFaces, face)
// calculate face edges
e0 := [3]float32{
vs[1][0] - vs[0][0],
vs[1][1] - vs[0][1],
vs[1][2] - vs[0][2],
}
e1 := [3]float32{
vs[2][0] - vs[0][0],
vs[2][1] - vs[0][1],
vs[2][2] - vs[0][2],
}
// calculate face normal
n0 := e0[1]*e1[2] - e0[2]*e1[1]
n1 := e0[2]*e1[0] - e0[0]*e1[2]
n2 := e0[0]*e1[1] - e0[1]*e1[0]
// normalize face normal
length := float32(math.Sqrt(float64((n0 * n0) + (n1 * n1) + (n2 * n2))))
if length > 0 {
n0 = n0 / length
n1 = n1 / length
n2 = n2 / length
}
n := []float32{
n0,
n1,
n2,
}
tempNormals = append(tempNormals, n)
return nil
}
for scanner.Scan() {
line := strings.TrimSpace(scanner.Text())
if line == "" {
continue
}
parts := strings.Fields(line)
if vertexCount > 0 {
var v []float32
for _, s := range parts[0:3] {
f, err := strconv.ParseFloat(s, 32)
if err != nil {
return err
}
v = append(v, float32(f))
}
tempVertices = append(tempVertices, v)
vertexCount--
} else if faceCount > 0 {
count, err := strconv.Atoi(parts[0])
if err != nil {
return err
}
if count > 3 {
// Convert Polygon to Triangles
for i := 1; i < count-1; i++ {
if err := addOffFace(parts[1], parts[i+1], parts[i+2]); err != nil {
return err
}
}
} else {
// Handle triangle
if err := addOffFace(parts[1:4]...); err != nil {
return err
}
}
faceCount--
} else {
fmt.Println("Ignoring:", line)
}
}
if err := scanner.Err(); err != nil {
return err
}
if smooth {
vns := make(map[int][]float32, count)
// Loop once to add face normals to vertex normals
for f, face := range tempFaces {
fn := tempNormals[f]
for i := 0; i < 3; i++ {
vn := vns[face[i]]
if vn == nil {
vn = []float32{0, 0, 0}
}
vn[0] += fn[0]
vn[1] += fn[1]
vn[2] += fn[2]
vns[face[i]] = vn
}
}
// Loop again to add tempNormals to normals
for _, face := range tempFaces {
for i := 0; i < 3; i++ {
vn := vns[face[i]]
// Normalize normal
length := float32(math.Sqrt(float64((vn[0] * vn[0]) + (vn[1] * vn[1]) + (vn[2] * vn[2]))))
if length > 0 {
vn[0] /= length
vn[1] /= length
vn[2] /= length
}
normals = append(normals, vn...)
}
}
} else {
for _, temp := range tempNormals {
// Add once for each vertex
for i := 0; i < 3; i++ {
normals = append(normals, temp...)
}
}
}
if err := d.AddMesh(id, count, vertices, normals); err != nil {
return err
}
return nil
}