Currently I am building an AR app with a function of AR navigation. I use JPCT-AE to render the 3D objects. Now I am facing a problem, in JPCT-AE camera we can set the near plane and far plane(default is near:1, far:1000), the unit I know it just depends. But as an AR navigation app, I need to know the relationship between JPCT-AE world distance and real world distance. For example, the mobile camera gets the scene and in the position of 2 meters away I need to turn left, then I need to tell JPCT-AE to put an arrow pointing to left 2 meters away. In this case I don't know how many units I need to translate.
Basically I can do some tests physically to determine the relationship but is there any theory related to this point, especially considering field of view (FOV)?
