Is it possible to clamp 3D tiles to Cesium World Terrain?

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

I am able to clamp KML and COLLADA data types to Cesium World terrain,

but then i uploaded the 3D tiles files there is no choice to clamp the models to the terrain.
Due to this the buildings are located below the terrain when Cesium World terrain are selected.
Is there any method on how to do this?

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

I need to do this so that the buildings are not located below the Cesium World Terrain

It isn’t currently possible, but I think we can add support for this, since it would potentially work the same way as clamping when you upload the source KML/COLLADA. I opened a feature request for this here:

What are you currently using to generate the 3D Tileset that you’re uploading?

currently i am using FME to create 3DTiles from SketchUP models.
I tried using triangulated models of cityGML, but ion rejected it.
Is there specification of the cityGML data type that is accepted by Cesium Ion?