3D animation over 2D game?

I am making a 2D game where a when a Player collects a certain item, the game wil have a dark transparency over the screen with a 3D version of the item twirling around. I know how to do the spinning item thing, but how do I get it so when I run some code the screen with have a dark transparency to it and then I can show the item. But the camera is moving around so the item has to be centered where the camera is?

Essentially, it is like how in the new Pokemon game are when you get a Gym Badge.

you mean the camera is spinning around the item, or the item is spinning in place? if the item just spins around its own axis, and the camera stays still, you could have a plane with a dark transparent texture be behind the item, so that the rest of what is in the scene looks darker.

A simple way would be to child the object to the camera, so they move together. As for making the screen darker, just render an black image on the UI and lower the alpha value.

The only problem that you might run into is having the object be in front of the UI rather than behind it. And while I’m pretty sure you can do this with a transparency shader, I’m not really sure how’d I’d go about doing it that specific way.