Re: [AD] rotate direction

[Jon Rafkind <workmin@xxxxxxxxxx>]

Trent Gamblin wrote:
> Writing some code for my game I came to realize that the C trig
> function sin behaves differently than the al_draw_rotated_*
> functions. "sin" starts at 0 (3 o'clock) and moves clockwise so that
> pi/2 is at 6 o'clock. The allegro functions however go counter
> clockwise, starting at the same 0 with pi/2 at 12 o'clock.
>   
Just to be clear, the reason for this is that sin(pi/2) is  and if you 
assume pi/2 is "up" and the top of the screen is y=0 then you really 
want to move in the negative direction.