uv-parser.js

const argv = require('yargs').argv;
const fs = require('fs');
const path = require('path');

const VERTEX_PER_FACE = 3;

let input = argv.input;

if (!input || !fs.existsSync(input)) {
    console.log('input file not found');
    process.exit(1);
}

let jsonList = JSON.parse(fs.readFileSync(input, 'utf8'));

jsonList.forEach((model, i) => {
    let level = model.level;

    let gltfPath = model.gltf_path;

    let absoluteGltfPath = path.resolve(gltfPath);

    let gltf = JSON.parse(fs.readFileSync(absoluteGltfPath, 'utf8'));

    let output = {
        gltf: path.basename(absoluteGltfPath),
        maps: []
    }

    if (gltf && gltf.scene) {

        console.log('cannot parse gltf file or scene');
        process.exit(1);
    }

    let primitiveUVMaps = new Array();

    gltf.scenes[gltf.scene].nodes.forEach((nodeIndex) => {
        let node = gltf.nodes[nodeIndex];

        if (!node.mesh) {
            return;
        }

        let nodeMesh = gltf.meshes[node.mesh];
        let nodeMeshPrimitives = nodeMesh.primitives;

        nodeMeshPrimitives.forEach((primitive) => {
            let primitiveMaterial = gltf.materials[primitive.material];

            if (primitiveMaterial.pbrMetallicRoughness) {
                if (primitiveMaterial.pbrMetallicRoughness.baseColorTexture) {
                    primitiveUVMaps.push({
                        uvAccessor: gltf.accessors[primitive.attributes["TEXCOORD_" + primitiveMaterial.pbrMetallicRoughness.baseColorTexture.texCoord]],
                        indexAccessor: gltf.accessors[primitive.indices],
                        image: gltf.images[gltf.textures[primitiveMaterial.pbrMetallicRoughness.baseColorTexture.index].source]
                    });
                }

                if (primitiveMaterial.pbrMetallicRoughness.metallicRoughnessTexture) {
                    primitiveUVMaps.push({
                        uvAccessor: gltf.accessors[primitive.attributes["TEXCOORD_" + primitiveMaterial.pbrMetallicRoughness.metallicRoughnessTexture.texCoord]],
                        indexAccessor: gltf.accessors[primitive.indices],
                        image: gltf.images[gltf.textures[primitiveMaterial.pbrMetallicRoughness.metallicRoughnessTexture.index].source]
                    });
                }
            }

            if (primitiveMaterial.normalTexture) {
                primitiveUVMaps.push({
                    uvAccessor: gltf.accessors[primitive.attributes["TEXCOORD_" + primitiveMaterial.normalTexture.texCoord]],
                    indexAccessor: gltf.accessors[primitive.indices],
                    image: gltf.images[gltf.textures[primitiveMaterial.normalTexture.index].source]
                });
            }

            if (primitiveMaterial.occlusionTexture) {
                primitiveUVMaps.push({
                    uvAccessor: gltf.accessors[primitive.attributes["TEXCOORD_" + primitiveMaterial.occlusionTexture.texCoord]],
                    indexAccessor: gltf.accessors[primitive.indices],
                    image: gltf.images[gltf.textures[primitiveMaterial.occlusionTexture.index].source]
                });
            }

            if (primitiveMaterial.emissiveTexture) {
                primitiveUVMaps.push({
                    uvAccessor: gltf.accessors[primitive.attributes["TEXCOORD_" + primitiveMaterial.emissiveTexture.texCoord]],
                    indexAccessor: gltf.accessors[primitive.indices],
                    image: gltf.images[gltf.textures[primitiveMaterial.emissiveTexture.index].source]
                });
            }
        });
    });

    if (primitiveUVMaps.length == 0) {
        console.log('no mapped texture images found');
        return;
    }

    primitiveUVMaps.forEach((map) => {
        let mapBufferView = gltf.bufferViews[map.uvAccessor.bufferView];
        let indexBufferView = gltf.bufferViews[map.indexAccessor.bufferView];

        let uvBufferPath = path.resolve(path.join(path.dirname(absoluteGltfPath), gltf.buffers[mapBufferView.buffer].uri));

        let uvBuffer = fs.readFileSync(uvBufferPath);

        let indexBufferPath = path.resolve(path.join(path.dirname(absoluteGltfPath), gltf.buffers[indexBufferView.buffer].uri));
        let indexBuffer = fs.readFileSync(indexBufferPath);

        // assume that all elements in uv maps are VEC2 : 5126 (FLOAT)
        if (map.uvAccessor.componentType != 5126 || map.uvAccessor.type != "VEC2") {
            console.log('this map is not using float values to map image textures');
            return;
        }

        let uvs = new Array();

        for (let i = 0; i < map.uvAccessor.count; i++) {
            let u = uvBuffer.readFloatLE(mapBufferView.byteOffset + 2 * i * 4);
            let v = uvBuffer.readFloatLE(mapBufferView.byteOffset + (2 * i + 1) * 4);
            uvs.push([u, v]);
        }

        let indices = new Array();
        let bytePerIndex = 2;

        if (map.indexAccessor.componentType == 5121) { // UNSIGNED_BYTE
            bytePerIndex = 1;
        } else if (map.indexAccessor.componentType == 5123) { // UNSIGNED_SHORT
            bytePerIndex = 2;
        } else if (map.indexAccessor.componentType == 5125) { // UNSIGNED_INT
            bytePerIndex = 4;
        } else {
            return;
        }

        for (let i = 0; i < map.indexAccessor.count; i++) {

            if (bytePerIndex == 1) {
                index = indexBuffer.readUInt8(indexBufferView.byteOffset + bytePerIndex * i);
            } else if (bytePerIndex == 2) {
                index = indexBuffer.readUInt16LE(indexBufferView.byteOffset + bytePerIndex * i);
            } else {
                index = indexBuffer.readUInt32LE(indexBufferView.byteOffset + bytePerIndex * i);
            }
            indices.push(index);
        }

        let faceUvs = new Array();

        for (let i = 0; i < (indices.length / VERTEX_PER_FACE); i++) {
            faceUvs.push([uvs[indices[VERTEX_PER_FACE * i]], uvs[indices[VERTEX_PER_FACE * i + 1]], uvs[indices[VERTEX_PER_FACE * i + 2]]]);
        }

        output.maps.push({
            image: map.image,
            faceUvs: faceUvs
        });
    });

    fs.writeFileSync(path.join(path.dirname(absoluteGltfPath), 'uv_coord.json'), JSON.stringify(output, null, 2), { encoding: 'utf8' });
});

process.exit(0);