I previously started this (very early this morning) in the beginners section, but have been advised to move it here. I'm currently working on a space combat game. To simplify some of my lod calculations, I'm trying to find the distance at which an object becomes invisible (ie: is less than 1 pixel wide or tall). All of my objects have a bounding sphere or radius r_obj. Supposing we have a horizontal field of view fov_x, and similarly a resolution res_x I had reasoned as follows:
d_critical = r_obj / tan( fov_x / 2res_x )
where d_critical is the distance at which the object takes up 1 pixel.
So far this is all very basic trig. And yet when I tested this method, I find that the critical distances are much larger than this predicts. Any ideas where I've gone wrong?