Seeing outside of enclosed spaces (e.g. cockpits with no windows)

Hello. I have been looking for ways to be able to view the outside of an enclosed space without physically doing it using windows or holes and such. Much like in this image:


So far the only method I’ve found is to use Render Targets to act like cameras and a material to display them on the model of a screen. This works perfectly, but it is a very expensive method to use performance-wise, which is an issue.
Since I’ve been unable to find any other ways to do this, im wondering if anyone else knows any other less expensive methods to view the outside of an enclosed space.

Another example of what im trying to achieve would be Titanfall’s titans, but with physical cockpits, not just an overlaid image.