I have encountered a strange behaviour of the vec_for_screen function, maybe someones knows of that.

I have got a top view camera and want to move an object below

VECTOR t;
t.x = ev->mouse_pos->x;
t.y = ev->mouse_pos->y;
t.z = _VAR(200);
vec_for_screen(&t,TopView);

So it's mainly that what the manual sasys (don't mind about the syntax difference, it's C++)

But the objects are not displayed properly. They are shifted.
The function works fine when I stand upright.
Anybody who succeed using it for a top view?

I had to same issue. As soon as I used a function like vec_for_screen() or vec_to_screen() things would move around to odd positions. I'm not sure how I resolved this issue but one day it just stopped happening.