what 3d model file types are supported？how load gltf model？
Cesium for Unity supports 3D Tiles and Terrain from Cesium ion. And it can drape Imagery over either of those.
If you have a glTF, you can upload it to Cesium ion to convert it to 3D Tiles.
Are there plans for glTF or glb formats?
We probably should do that, as it would be reasonably straightforward to do based on what we already have. But it’s not a particularly high priority because there are other ways to load a glTF in Unity.
I’m a little confused, is there a way to convert czml files into 3D Tiles? I see some sandcastle examples that use czml, but it’s not clear to me how this translates to 3D Tiles, and from there import to Unity.
No, sorry, there’s no automatic way to convert CZML to 3D Tiles.