Attach button to 3D object,How to attach a button to 3D object (.obj)

Hi, i have an app for android and i have a 3D object (person) and i want that some parts of the object can be clickable (touch), so i thought that i can do that with a button but idk how to attach it to the 3D object.Also the body can be rotated and you can zoom in/out, so idk if that can be a problem if i put a static button on the screen,Hi, know i have a body object 3D, i want to make some parts of the body clickable, i imagine that i can do that with a button.Also you can rotate the body and zoom in, zoom out