objをjsonに変更するnode.js

package.json

{
  "name": "parser_nodejs",
  "version": "1.0.0",
  "main": "index.js",
  "scripts": {
    "start": "node parser.js"
  },
  "license": "MIT",
  "dependencies": {
    "minimist": "^1.2.0",
    "parse-obj": "^0.0.0"
  }
}

parser.js

// yarn start -f your_file -p 2
// parse obj file with index attributes

var fs = require("fs");
var parseOBJ = require("parse-obj");
var argv = require("minimist")(process.argv.slice(2));

var fileName = argv.f;
var precisoin = argv.p;

if (precisoin < 0 || !precisoin) {
  precision = 3;
}

if (!fileName) {
  console.log(
    "you missed fileName. yarn start -f your_file -p detail_of_number"
  );
  return;
}

parseOBJ(fs.createReadStream(`./assets/${fileName}.obj`), function(
  err,
  result
) {
  if (err) {
    throw new Error("Error parsing OBJ file: " + err);
  }

  var dataObj = {};
  updateVertex(result, dataObj);
  updateNormals(result, dataObj);
  updateUvs(result, dataObj);
  updateIndex(result, dataObj);

  writeObjFile(dataObj);
});
function updateVertex(result, dataObj){
  dataObj.verts = [];

  
  for (let ii = 0; ii < result.facePositions.length; ii++) {
    for (let jj = 0, length = result.facePositions[ii].length - 2; jj < length; jj++) {
      // dataObj.index[ii][jj] = Number(dataObj.index[ii][jj].toFixed(precisoin));
      let index0 = (0 + jj * 2 ) % result.facePositions[ii].length;
      let index1 = (1 + jj * 2 ) % result.facePositions[ii].length;
      let index2 = (2 + jj * 2 ) % result.facePositions[ii].length;

      let faceIndex0 = result.facePositions[ii][index0];
      let faceIndex1 = result.facePositions[ii][index1];
      let faceIndex2 = result.facePositions[ii][index2];

      let pos0 = result.vertexPositions[faceIndex0];
      let pos1 = result.vertexPositions[faceIndex1];
      let pos2 = result.vertexPositions[faceIndex2];
      
      dataObj.verts.push(
        Number(pos0[0].toFixed(precision)), Number(pos0[1].toFixed(precision)), Number(pos0[2].toFixed(precision)), 
        Number(pos1[0].toFixed(precision)), Number(pos1[1].toFixed(precision)), Number(pos1[2].toFixed(precision)), 
        Number(pos2[0].toFixed(precision)), Number(pos2[1].toFixed(precision)), Number(pos2[2].toFixed(precision))
      );

    }
  }
}


function updateNormals(result, dataObj) {
  dataObj.normals = [];
  
  for (let ii = 0; ii < result.faceNormals.length; ii++) {
    for (let jj = 0, length = result.faceNormals[ii].length - 2; jj < length; jj++) {
      // dataObj.index[ii][jj] = Number(dataObj.index[ii][jj].toFixed(precisoin));
      let index0 = (0 + jj * 2 ) % result.faceNormals[ii].length;
      let index1 = (1 + jj * 2 ) % result.faceNormals[ii].length;
      let index2 = (2 + jj * 2 ) % result.faceNormals[ii].length;

      let faceIndex0 = result.faceNormals[ii][index0];
      let faceIndex1 = result.faceNormals[ii][index1];
      let faceIndex2 = result.faceNormals[ii][index2];

      let pos0 = result.vertexNormals[faceIndex0];
      let pos1 = result.vertexNormals[faceIndex1];
      let pos2 = result.vertexNormals[faceIndex2];
      
      // dataObj.normals.push(pos0[0], pos0[1], pos0[2], pos1[0], pos1[1], pos1[2], pos2[0], pos2[1], pos2[2]);
      dataObj.normals.push(
        Number(pos0[0].toFixed(precision)), Number(pos0[1].toFixed(precision)), Number(pos0[2].toFixed(precision)), 
        Number(pos1[0].toFixed(precision)), Number(pos1[1].toFixed(precision)), Number(pos1[2].toFixed(precision)), 
        Number(pos2[0].toFixed(precision)), Number(pos2[1].toFixed(precision)), Number(pos2[2].toFixed(precision))
      );
    }
  }
}

function updateUvs(result, dataObj) {
  // dataObj
  dataObj.texcoords = [];

  for (let ii = 0; ii < result.faceUVs.length; ii++) {
    for (let jj = 0, length = result.faceUVs[ii].length - 2; jj < length; jj++) {
      // dataObj.index[ii][jj] = Number(dataObj.index[ii][jj].toFixed(precisoin));
      let index0 = (0 + jj * 2 ) % result.faceUVs[ii].length;
      let index1 = (1 + jj * 2 ) % result.faceUVs[ii].length;
      let index2 = (2 + jj * 2 ) % result.faceUVs[ii].length;

      let faceIndex0 = result.faceUVs[ii][index0];
      let faceIndex1 = result.faceUVs[ii][index1];
      let faceIndex2 = result.faceUVs[ii][index2];

      let pos0 = result.vertexUVs[faceIndex0];
      let pos1 = result.vertexUVs[faceIndex1];
      let pos2 = result.vertexUVs[faceIndex2];
      
      // dataObj.texcoords.push(pos0[0], pos0[1], pos1[0], pos1[1], pos2[0], pos2[1]);
      dataObj.texcoords.push(
        Number(pos0[0].toFixed(precision)), Number(pos0[1].toFixed(precision)),  
        Number(pos1[0].toFixed(precision)), Number(pos1[1].toFixed(precision)),  
        Number(pos2[0].toFixed(precision)), Number(pos2[1].toFixed(precision))
      );

    } 
  }

}


function updateIndex(result, dataObj) {
  dataObj.indices = [];

  for (let ii = 0; ii < result.facePositions.length; ii++) {
    let cnt;
    if(result.facePositions[ii].length === 3) cnt = 3;
    else cnt = 6;

    for(let jj = 0; jj < cnt; jj++){
      dataObj.indices.push(dataObj.indices.length)
    }

  }
}



function writeObjFile(dataObj) {
  console.log(dataObj.indices.length);
  console.log(dataObj.verts.length);

  const content = JSON.stringify(dataObj);

  fs.writeFile(`./output/${fileName}.json`, content, "utf8", function(err) {
    if (err) {
      return console.log(err);
    }

    console.log("json file was saved.");
  });
}