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Rotating To Face a Point
1 answer
I need some help with rotating sprites towards the mouse. I'm currently using the library allegro 5.XX. The rotation of the sprite works but it's constantly inaccurate. It's always a few angles
off from the mouse to the left. Can anyone please help me with this? Thank you.
P.S I got help with the rotating function from here: http://www.gamefromscratch.com/post/2012/11/18/GameDev-math-recipes-Rotating-to-face-a-point.aspx
Although it's by javascript, the maths function is the same. And also, by placing:
if(angle < 0)
{
angle = 360 - (-angle);
}
doesn't fix it.
The Code:
#include <allegro5\allegro.h>
#include <allegro5\allegro_image.h>
#include "math.h"
int main(void)
{
int width = 640;
int height = 480;
bool exit = false;
int shipW = 0;
int shipH = 0;
ALLEGRO_DISPLAY *display = NULL;
ALLEGRO_EVENT_QUEUE *event_queue = NULL;
ALLEGRO_BITMAP *ship = NULL;
if(!al_init()) return -1;
display = al_create_display(width, height);
if(!display)
return -1;
al_install_keyboard();
al_install_mouse();
al_init_image_addon();
al_set_new_bitmap_flags(ALLEGRO_MIN_LINEAR | ALLEGRO_MAG_LINEAR); //smoother rotate
ship = al_load_bitmap("ship.bmp");
shipH = al_get_bitmap_height(ship);
shipW = al_get_bitmap_width(ship);
int shipx = width/2 - shipW/2;
int shipy = height/2 - shipH/2;
int mx = width/2;
int my = height/2;
al_set_mouse_xy(display, mx, my);
event_queue = al_create_event_queue();
al_register_event_source(event_queue, al_get_mouse_event_source());
al_register_event_source(event_queue, al_get_keyboard_event_source());
//al_hide_mouse_cursor(display);
float angle;
while(!exit)
{
ALLEGRO_EVENT ev;
al_wait_for_event(event_queue, &ev);
if(ev.type == ALLEGRO_EVENT_KEY_UP)
{
switch(ev.keyboard.keycode)
{
case ALLEGRO_KEY_ESCAPE:
exit = true;
break;
/*case ALLEGRO_KEY_LEFT:
degree -= 10;
break;
case ALLEGRO_KEY_RIGHT:
degree += 10;
break;*/
case ALLEGRO_KEY_W:
shipy -=10;
break;
case ALLEGRO_KEY_S:
shipy +=10;
break;
case ALLEGRO_KEY_A:
shipx -=10;
break;
case ALLEGRO_KEY_D:
shipx += 10;
break;
}
}else if(ev.type == ALLEGRO_EVENT_MOUSE_AXES)
{
mx = ev.mouse.x;
my = ev.mouse.y;
angle = atan2(my - shipy, mx - shipx);
}
// al_draw_bitmap(ship,shipx, shipy, 0);
//al_draw_rotated_bitmap(ship, shipW/2, shipH/2, shipx, shipy, degree * 3.142/180,0);
al_draw_rotated_bitmap(ship, shipW/2, shipH/2, shipx, shipy,angle, 0);
//I directly placed the angle because the allegro library calculates radians, and if i multiplied it by 180/3. 142 the rotation would go hawire, not would, it actually did.
al_flip_display();
al_clear_to_color(al_map_rgb(0,0,0));
}
al_destroy_bitmap(ship);
al_destroy_event_queue(event_queue);
al_destroy_display(display);
return 0;
}
EDIT: This was marked duplicate by a moderator. I'd like to say that this isn't the same as that. I'm a total beginner at game programming, I had a view at that other
topic and I had difficulty understanding it. Please understand this, thank you. :/
Also, while I was making a print of what the angle is I got this...
Here is a screenshot:http://img34.imageshack.us/img34/7396/fzuq.jpg
Which is weird because aren't angles supposed to be 360 degrees only?
