How small can I set the scale of World Terrain ?
The minimum now that I can set is : Scale : 0,000002
Can I remove this barrier and make it smaller ? I want the player to rotate it with a hand gesture and view the globe in front of her like a basketball.
As far as I know, 0.000002 is the minimum size that Cesium World Terrain will render at in Unreal. Some possible workarounds to this are discussed in this thread - Modifying Map scale in Unreal - #6 by jlundy
If the player will be holding and rotating the globe like that, I’d definitely recommend using a regular mesh instead of Cesium World Terrain. If you need to also view the world at large scale, you can swap between them rather than scaling it up. I don’t think that the Cesium Georeference will play nicely with transformations like that to the tileset.
That being said, there likely is a way to hack it by modifying the plugin code. If you decide to try that, let me know how it goes!