CesiumForUnreal achieves the effect of sticking to the ground (SurfacePolygon)

1. Achieve goals

The Cesium-Unreal plug-in based on UE5 adds the online world terrain Cesium World Terrain, draws the Polygon surface on the terrain surface, and makes it close to the terrain to achieve the 贴地面（SurfacePolygon）effect. The GIF animation is as follows:

2. Implementation process

Here is the effect of sticking to the ground directly using the method provided by CesiumForUnreal, so it only produces effects on 3dtiles (but in the process of using UE for GIS development, CesiumForUnreal is generally used to load terrain), and later it will be based on UE's native functions and methods ( Such as RT+De