У вашего броузера проблема в совместимости с HTML5
Convert Any Mesh To Unity Terrain.By using this script, you can easily convert (.obj or .fbx) mesh to Unity Terrain.
Here is the link to the script
https://www.mediafire.com/file/3oyvdjcjix2d3iu/Object2Terrain.cs
If you like it .please subscribe my channel :)