Maximum angle of incidence?

This question is a little difficult to describe in writing- is there a maximum angle of incidence from perimeter glazing for a “direct line of sight?” If you are directly in front of the window looking out, it could be considered perpendicular or 90 degrees; as you move laterally away from the window the angle of your view would become more incidental. At what point does it no longer constitute a “direct line of sight?” I can test it out in our 3D model by checking with perspective views, but I’m wondering if there’s an official cutoff.