b3dm是⼀个缩写，它的全称是：Batched 3D Mode(批量化3d模型)。
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 the fly for changing a model’s appearance, e.g., changing highlight color based on a property value.
A Batched 3D Model tile is a binary blob in little endian.
特别值得注意的是。b3dm数据也是基于gltf的，也就是说批量的模型中的单个模型的模型格式还是gltf，并且数据组织⽅式也和之前gltf是⼀样的。说⽩了b3dm就是在原来gltf⼩模型，单个模型的基础之上，做了批量化的数据组织⽅式，多了feature table和batch table两个⽂件。
参考：https://blog.csdn.net/weixin_44040023/article/details/126785109
