How to draw camera "viewport" on the plot?

I want to draw camera's "viewport" on the plot. By saying "Viewport" I mean the borders of the "photo" on the following figure:

According to the manual, the "viewport" is defined by the CameraViewAngle parameter and the orientation of the axes.

I can draw the "viewport" rectangle using the following function:

annotation(gcf,'rectangle','Position', [x, y, w, h]);

where [x,y,w,h] are the coordinates of the rectangle in figure's "normalized coordinates". The question is: how can I get these coordinates?

P.S. To draw the "viewport" one needs the aspect ratio of the "photo". Let us assume that the aspect ratio is 4/3.