上篇文章我们知道了什么叫gltf，不知道的可以去看一看

这篇文章来了解一下什么是b3dm。

首先，b3dm是一个缩写，它的全称是：Batched 3D Mode(批量化3d模型)，顾名思义，批量化指的是一定有很多个，不止一个。

Batched 3D Model allows offline batching of heterogeneous 3D models, such as different buildings in a city, for efficient streaming to a web client for rendering and interaction. Efficiency comes from transferring multiple models in a single request and rendering them in the least number of WebGL draw calls necessary. Using the core 3D Tiles spec language, each model is a feature.

Per-model properties, such as IDs, enable individual models to be identified and updated at runtime, e.g., show/hide, highlight color, etc. Properties may be used, for example, to query a web service to access metadata, such as passing a building's ID to get its address. Or a property might be referenced on