vox-to-box.js

// install:
//
//   npm install ndarray parse-magica-voxel
//
// usage:
//
//  node vox-to-box.js my-file.vox > my-file.terrain
//

const parseMagicaVoxel = require('parse-magica-voxel')
const ndarray = require('ndarray')
const fs = require('fs')

function compress (voxels) {
    const {
        data,
        shape: [nx, ny, nz],
        stride: [sx, sy, sz],
        offset,
    } = voxels;

    const rle = [];

    let prevBlock = -1;
    let runLength = 0;

    let ptr = offset;
    const stepi = sx;
    const stepj = sy - sx * nx;
    const stepk = sz - sy * ny;
    for (let k = 0; k < nz; ++k) {
        for (let j = 0; j < ny; ++j) {
            for (let i = 0; i < nx; ++i) {
                const b = data[ptr];
                if (b !== prevBlock || runLength >= 65535) {
                    if (runLength) {
                        if (runLength >= 255) {
                            rle.push(
                                255,
                                runLength >> 8,
                                runLength & 0xff);
                        } else {
                            rle.push(runLength);
                        }
                        if (prevBlock >= 255) {
                            rle.push(
                                255,
                                prevBlock >> 8,
                                prevBlock & 0xff);
                        } else {
                            rle.push(prevBlock);
                        }
                    }
                    runLength = 0;
                    prevBlock = b;
                }
                runLength += 1;
                ptr += stepi;
            }
            ptr += stepj;
        }
        ptr += stepk;
    }

    if (runLength >= 255) {
        rle.push(
            255,
            runLength >> 8,
            runLength & 0xff);
    } else {
        rle.push(runLength);
    }
    if (prevBlock >= 255) {
        rle.push(
            255,
            prevBlock >> 8,
            prevBlock & 0xff);
    } else {
        rle.push(prevBlock);
    }

    return rle;
}

function convertMagicaVoxelToBox (buffer) {
    const data = parseMagicaVoxel(buffer)
    if (!data.PACK) {
        throw new Error('multiple chunks in file')
    }
    const shape = [
        data.SIZE.x,
        data.SIZE.y,
        data.SIZE.z
    ]
    const result = new ndarray(new Uint8Array(shape[0] * shape[1] * shape[2]), shape)
    for (var k = 0; k < data.XYZI.length; ++k) {
        const {x, y, z, c} = data.XYZI[k]
        result.set(x, y, z, c | 0)
    }
    return result.transpose(1, 2, 0)
}

function patchBCMTemplate(rle, size) {
    return JSON.stringify({
        encoded: rle,
        map_size: size,
        "TERRAIN": "MagicaVoxel"
    })
}

const data = fs.readFileSync(process.argv[2])
const voxels = convertMagicaVoxelToBox(data)
const rle = compress(voxels)
const result = patchBCMTemplate(rle, voxels.shape[0])

console.log(result)