very basic bitmap animation

DuncanShine

I have created two images that are supposed to be part of a character's animation cycle, and I want to rapidly switch between the two images, like a run cycle. However, just doing this makes the image change way too quickly, and adding a delay with Sleep() would slow down the whole program so i'm stuck as to how i would do it

Edgar Reynaldo

The key is measuring time without delaying the program. A timer will work for this, as will al_wait_for_vsync, or simply al_get_time.

Decide the duration of the animation in seconds, determine how many frames you have and then to get the current animation frame, use fmod.

#SelectExpand
  1#include <allegro5/allegro.h>
  2...
  3const double FPS = 60.0;
  4const double SPF = 1.0/FPS;
  5
  6ALLEGRO_EVENT_QUEUE* queue = al_create_event_queue();
  7ALLEGRO_TIMER* timer = al_create_timer(SPF);
  8if (!timer) {Fail();}
  9al_register_event_source(queue , al_get_timer_event_source(timer));
 10
 11double duration = 2.0;/// 2 seconds for 2 frames
 12int nframes = 2;
 13double elapsed_time;
 14
 15al_start_timer(timer);
 16
 17/// In event loop
 18while (!quit) {
 19   if (redraw) {
 20      al_clear_to_color(al_map_rgb(255,255,255));
 21      int FRAME_NUM = (int)nframes*fmod(elapsed_time , duration)/duration;
 22      al_draw_bitmap(bitmaps[FRAME_NUM] , 0 , 0);
 23      al_flip_display();
 24      redraw = false;
 25   }
 26
 27   do {
 28      ALLEGRO_EVENT ev;
 29      al_wait_for_event(queue , &ev);
 30      if (ev.type == ALLEGRO_EVENT_TIMER) {
 31         elapsed_time += SPF;
 32         redraw = true;
 33      }
 34   } while (!al_is_event_queue_empty(queue));
 35};
 36return 0;
 37}

Niunio

[edit]I was distracted and Edgar send it before me, but I think mine is simpler.[/edit]

Keep track about how many time the animation frame is on screen:

#SelectExpand
  1  typedef struct {
  2    int frame, cnt
  3  } ANIMATION_STATE;
  4
  5  ANIMATION_STATE MySpriteState;
  6
  7...
  8
  9/* Initialization */
 10  MySpriteState.frame = FIRST_FRAME_NDX; MySpriteState.cnt = 0;
 11
 12....
 13/* At updating. */
 14  if (++MySpriteState.cnt > MAX_TIME_FRAME) {
 15    MySpriteState.cnt = 0;
 16    if (++MySpriteState.frame >= NUM_FRAMES) MySpriteState.frame = FIRST_FRAME_NDX;
 17  }
 18...

DuncanShine

This all works, how would i modify it to happen when the character is moving in a specific direction?

Niunio

Not sure what do you mean...

DuncanShine

well i've made it so that when you change direction, the character does the opposite animation but the problem is a huge delay between pressing the button and the character actually moving.

Niunio

Without actual code is hard to say. Maybe you should take a look to the Allegro Vivace tutorial.

Thread #618058. Printed from Allegro.cc