what is the importance of B3DM ?

1. A concise explanation of the problem you’re experiencing.

why we use b3dm file in the json file ?

and suppose i already have b3dm file of particular region … then how to create a json file …and run on cesium ?

please anyone explain me ?

2. A minimal code example. If you’ve found a bug, this helps us reproduce and repair it.

3. Context. Why do you need to do this? We might know a better way to accomplish your goal.

4. The Cesium version you’re using, your operating system and browser.

Take a look at the 3D Tiles specification for a starting point.

You can load valid 3D tiles in Cesium like in this example.