Welcome to the Cesium community!
I’m looking into why new members can’t upload images - in the meantime I’ve manually increased your “trust level” so you should be able to post images now I think.
How are you viewing the mesh? Are you using Cesium Stories, or a custom CesiumJS app?
Generally, when you upload a large model and tile it into 3D Tiles, it’ll stream in the model based on how close the camera is, how large the screen resolution is etc so you can view models of any scale without overwhelming the device memory/resources.
If you’re viewing the 3D Tileset in CesiumJS, you can tweak the quality setting using the maximumScreenSpaceError parameter. If you click on “Open code example” under the asset preview window in Cesium ion, that’ll open the online coding environment, where you can test this, like this:
var tileset = new Cesium.Cesium3DTileset({
url: Cesium.IonResource.fromAssetId(YOUR_ASSET_ID),
maximumScreenSpaceError: 8// The defaults to 16. Lower is higher quality.
});