code: function rebuildAttribute (attrib, data, itemSize) {
    if (attrib.itemSize !== itemSize) return true
    if (!attrib.array) return true
    var attribLength = attrib.array.length
    if (Array.isArray(data) && Array.isArray(data[0])) {
      // [ [ x, y, z ] ]
      return attribLength !== data.length * itemSize
    } else {
      // [ x, y, z ]
      return attribLength !== data.length
    }
    return false
  }
docs: Test whether the attribute needs to be re-created, returns false if we can re-use it as-is.