官网下载速度太慢了
访问下面链接快速下载
https://download.visualstudio.microsoft.com/download/pr/3136e217-e5b7-4899-9b7e-aa52ecb8b108/d74134edaa75e3300f8692660b9fb7b5/windowsdesktop-runtime-6.0.26-win-x64.exe
cesium for unity 源码包：https://github.com/CesiumGS/cesium-unity/releases/tag/v1.23.1
示例包 https://github.com/CesiumGS/cesium-unity-samples/releases/tag/v1.23.2