Native Babylon.js function

To easily merge a number of meshes to a single mesh use the static MergeMeshes of the Mesh class:

var newMesh = BABYLON.Mesh.MergeMeshes(arrayOfMeshes[, disposeSource, allow32BitsIndices, meshSubclass]);

variable	description
arrayOfMeshes	An array of Meshes. They should all be of the same material.
disposeSource (optional)	When true (default), the source meshes will be disposed upon completion.
allow32BitsIndices (optional)	When the sum of the vertices > 64k, this must be set to true.
meshSubclass (optional)	When set, vertices inserted into this Mesh. Meshes can then be merged into a Mesh sub-class.

Use your own merge function

If you want to merge meshes into a new one using a self implemented function, you can use the following code as basis and improve it to your needs:

Note: Careful, when you merge cloned mesh, you need to update the world matrix of the mesh with computeWorldMatrix before calling the function.

Note: This article covers the internal merging process. You can also use BABYLON.VertexData object and its merge() function for a simpler solution.

var mergeMeshes = function (meshName, arrayObj, scene) {
    var arrayPos = [];
    var arrayNormal = [];
    var arrayUv = [];
    var arrayUv2 = [];
    var arrayColor = [];
    var arrayMatricesIndices = [];
    var arrayMatricesWeights = [];
    var arrayIndice = [];
    var savedPosition = [];
    var savedNormal = [];
    var newMesh = new BABYLON.Mesh(meshName, scene);
    var UVKind = true;
    var UV2Kind = true;
    var ColorKind = true;
    var MatricesIndicesKind = true;
    var MatricesWeightsKind = true;

    for (var i = 0; i != arrayObj.length ; i++) {
        if (!arrayObj[i].isVerticesDataPresent([BABYLON.VertexBuffer.UVKind]))
            UVKind = false;
        if (!arrayObj[i].isVerticesDataPresent([BABYLON.VertexBuffer.UV2Kind]))
            UV2Kind = false;
        if (!arrayObj[i].isVerticesDataPresent([BABYLON.VertexBuffer.ColorKind]))
            ColorKind = false;
        if (!arrayObj[i].isVerticesDataPresent([BABYLON.VertexBuffer.MatricesIndicesKind]))
            MatricesIndicesKind = false;
        if (!arrayObj[i].isVerticesDataPresent([BABYLON.VertexBuffer.MatricesWeightsKind]))
            MatricesWeightsKind = false;
    }

    for (i = 0; i != arrayObj.length ; i++) {
        var ite = 0;
        var iter = 0;
        arrayPos[i] = arrayObj[i].getVerticesData(BABYLON.VertexBuffer.PositionKind);
        arrayNormal[i] = arrayObj[i].getVerticesData(BABYLON.VertexBuffer.NormalKind);
        if (UVKind)
            arrayUv = arrayUv.concat(arrayObj[i].getVerticesData(BABYLON.VertexBuffer.UVKind));
        if (UV2Kind)
            arrayUv2 = arrayUv2.concat(arrayObj[i].getVerticesData(BABYLON.VertexBuffer.UV2Kind));
        if (ColorKind)
            arrayColor = arrayColor.concat(arrayObj[i].getVerticesData(BABYLON.VertexBuffer.ColorKind));
        if (MatricesIndicesKind)
            arrayMatricesIndices = arrayMatricesIndices.concat(arrayObj[i].getVerticesData(BABYLON.VertexBuffer.MatricesIndicesKind));
        if (MatricesWeightsKind)
            arrayMatricesWeights = arrayMatricesWeights.concat(arrayObj[i].getVerticesData(BABYLON.VertexBuffer.MatricesWeightsKind));

        var maxValue = savedPosition.length / 3;

        arrayObj[i].computeWorldMatrix(true);
        var worldMatrix = arrayObj[i].getWorldMatrix();

        for (var ite = 0 ; ite != arrayPos[i].length; ite += 3) {
            var vertex = new BABYLON.Vector3.TransformCoordinates(new BABYLON.Vector3(arrayPos[i][ite], arrayPos[i][ite + 1], arrayPos[i][ite + 2]), worldMatrix);
            savedPosition.push(vertex.x);
            savedPosition.push(vertex.y);
            savedPosition.push(vertex.z);
        }

        for (var iter = 0 ; iter != arrayNormal[i].length; iter += 3) {
            var vertex = new BABYLON.Vector3.TransformNormal(new BABYLON.Vector3(arrayNormal[i][iter], arrayNormal[i][iter + 1], arrayNormal[i][iter + 2]), worldMatrix);
            savedNormal.push(vertex.x);
            savedNormal.push(vertex.y);
            savedNormal.push(vertex.z);
        }

        var tmp = arrayObj[i].getIndices();
        for (it = 0 ; it != tmp.length; it++) {
            arrayIndice.push(tmp[it] + maxValue);
        }
        arrayIndice = arrayIndice.concat(tmp);

        arrayObj[i].dispose(false);
    }

    newMesh.setVerticesData(BABYLON.VertexBuffer.PositionKind, savedPosition, false);
    newMesh.setVerticesData(BABYLON.VertexBuffer.NormalKind, savedNormal, false);
    if (arrayUv.length > 0)
        newMesh.setVerticesData(BABYLON.VertexBuffer.UVKind, arrayUv, false);
    if (arrayUv2.length > 0)
        newMesh.setVerticesData(BABYLON.VertexBuffer.UV2Kind, arrayUv, false);
    if (arrayColor.length > 0)
        newMesh.setVerticesData(BABYLON.VertexBuffer.ColorKind, arrayUv, false);
    if (arrayMatricesIndices.length > 0)
        newMesh.setVerticesData(BABYLON.VertexBuffer.MatricesIndicesKind, arrayUv, false);
    if (arrayMatricesWeights.length > 0)
        newMesh.setVerticesData(BABYLON.VertexBuffer.MatricesWeightsKind, arrayUv, false);

    newMesh.setIndices(arrayIndice);
    return newMesh;
};