In the Mesh Renderer component you can select if that object will cast and receive shadows. So if there are some 3D objects that you don't want to have a shadow, just disable **Shadow Casting** and **Shadow Receiving** in the chosen model’s Mesh Renderer component. I found that from [here][1].


 [1]: https://forum.unity.com/threads/solved-disable-shadows-per-gameobject.314495/