Firstly, I believe that there are some conditions needed for the car to appear on the field, and also i assume that you will want to have more than one car in the future.
I believe it's a bad idea to put all logic into the field objects, the only reason to do so would be performance reasons. But since you have a clear separation of concerns in your case, I ...
all you need is this link. in perspective we dont have axact bound but we have bounds in distance. you have to calculate camera distance from you object and calculate bound on that distance.
if its in 3d you can calculate using below:
public static class CameraExtensions
public static ...