BufferGeometry Cube with MultiMaterial faces

cube.json

{
    "metadata": {
        "version": 4.3,
        "type": "Object",
        "description": "BufferGeometry Cube Mesh with 6 Materials"
    },
    "object": {
        "uuid": "89529CC6-CBAC-412F-AFD1-FEEAE785BA19",
        "name": "Cube",
        "type": "Mesh",
        "matrix": [1,0,0,0,0,1,0,0,0,0,1,0,0,0,0,1],
        "geometry": "C3BF1E70-0BE7-4E6D-B184-C9F1E84A3423",
        "material": "87D95D6C-6BB4-4B8F-8166-A3A6945BFF00",
        "children": [
        ]       
    },
    "geometries": [
        {
            "uuid": "C3BF1E70-0BE7-4E6D-B184-C9F1E84A3423",
            "type": "BufferGeometry",
            "data": {
                "attributes": {
                    "position": {
                        "itemSize": 3,
                        "type": "Float32Array",
                        "array": [
                            -1, -1,  1,  1, -1,  1,  1,  1,  1, -1,  1,  1,
                             1, -1,  1,  1, -1, -1,  1,  1, -1,  1,  1,  1,
                             1, -1, -1, -1, -1, -1, -1,  1, -1,  1,  1, -1,
                            -1, -1, -1, -1, -1,  1, -1,  1,  1, -1,  1, -1,
                            -1,  1,  1,  1,  1,  1,  1,  1, -1, -1,  1, -1,
                            -1, -1, -1,  1, -1, -1,  1, -1,  1, -1, -1,  1
                        ]
                    },
                    "normal": {
                        "itemSize": 3,
                        "type": "Float32Array",
                        "array": [
                             0,  0,  1,  0,  0,  1,  0,  0,  1,  0,  0,  1,
                             1,  0,  0,  1,  0,  0,  1,  0,  0,  1,  0,  0,
                             0,  0, -1,  0,  0, -1,  0,  0, -1,  0,  0, -1,
                            -1,  0,  0, -1,  0,  0, -1,  0,  0, -1,  0,  0,
                             0,  1,  0,  0,  1,  0,  0,  1,  0,  0,  1,  0,
                             0, -1,  0,  0, -1,  0,  0, -1,  0,  0, -1,  0
                        ]
                    },
                    "uv": {
                        "itemSize": 2,
                        "type": "Float32Array",
                        "array": [
                            0.0, 1.0, 1.0, 1.0, 1.0, 0.0, 1.0, 0.0,
                            0.0, 1.0, 1.0, 1.0, 1.0, 0.0, 1.0, 0.0,
                            0.0, 1.0, 1.0, 1.0, 1.0, 0.0, 1.0, 0.0,
                            0.0, 1.0, 1.0, 1.0, 1.0, 0.0, 1.0, 0.0,
                            0.0, 1.0, 1.0, 1.0, 1.0, 0.0, 1.0, 0.0,
                            0.0, 1.0, 1.0, 1.0, 1.0, 0.0, 1.0, 0.0
                        ]
                    }
                },
                "index": {
                   "itemSize": 1,
                    "type": "Uint32Array",
                    "array": [
                         0,  1,  2,  2,  3,  0,
                         4,  5,  6,  6,  7,  4,
                         8,  9, 10, 10, 11,  8,
                        12, 13, 14, 14, 15, 12,
                        16, 17, 18, 18, 19, 16,
                        20, 21, 22, 22, 23, 20
                    ]
                },
                "groups": [
                    { "start":  0, "count": 6, "materialIndex": 0 },
                    { "start":  6, "count": 6, "materialIndex": 1 },
                    { "start": 12, "count": 6, "materialIndex": 2 },
                    { "start": 18, "count": 6, "materialIndex": 3 },
                    { "start": 24, "count": 6, "materialIndex": 4 },
                    { "start": 30, "count": 6, "materialIndex": 5 }
                ],
                "boundingSphere": {
                    "center": [ 0, 0, 0 ],
                    "radius": 1.414214
                }
            }
        }
    ],
    "materials": [
        {
            "uuid": "87D95D6C-6BB4-4B8F-8166-A3A6945BFF00",
            "type": "MultiMaterial",
            "materials": [
                {
                    "uuid": "87D95D6C-6BB4-4B8F-8166-A3A6945BFF01",
                    "type": "MeshPhongMaterial",
                    "color": 16724787,
                    "specular": 3355443,
                    "shininess": 15
                },
                {
                    "uuid": "87D95D6C-6BB4-4B8F-8166-A3A6945BFF02",
                    "type": "MeshPhongMaterial",
                    "color": 3407667,
                    "specular": 3355443,
                    "shininess": 15
                },
                {
                    "uuid": "87D95D6C-6BB4-4B8F-8166-A3A6945BFF03",
                    "type": "MeshPhongMaterial",
                    "color": 3355647,
                    "specular": 3355443,
                    "shininess": 15
                },
                {
                    "uuid": "87D95D6C-6BB4-4B8F-8166-A3A6945BFF04",
                    "type": "MeshPhongMaterial",
                    "color": 16777011,
                    "specular": 3355443,
                    "shininess": 15
                },
                {
                    "uuid": "87D95D6C-6BB4-4B8F-8166-A3A6945BFF05",
                    "type": "MeshPhongMaterial",
                    "color": 16724991,
                    "specular": 3355443,
                    "shininess": 15
                },
                {
                    "uuid": "87D95D6C-6BB4-4B8F-8166-A3A6945BFF06",
                    "type": "MeshPhongMaterial",
                    "color": 3407871,
                    "specular": 3355443,
                    "shininess": 15
                }
            ]
        }
    ]
}