no-reply@allegro.cc (djtschke) — Wed, 03 Aug 2011 19:37:54 +0000

Hello everbody,

I am quite new to C++ and Allegro and started by following this tutorial Demoscene C++ Allegro Tutorial. I was even able to convert the code to Allegro Version 5 and everything worked fine. Then I started on the task with the snow piling up (at the bottom part of the Tutorial). After a while I also managed to solve this task. Now my problem is that the application is running very slow as you will see if you compile it by yourself. I guess this is because I am working with a Bitmap. My question now is how can I speed up the whole application ?

Here is the code:

#SelectExpand
   1#include 
   2#include 
   3#include 
   4
   5using namespace std;
   6
   7// data structures for snow flaxes = very simple
   8const int total_flakes=900;
   9const int total_layers=3;
  10
  11struct particle
  12{
  13    int x,y;
  14    int layer;
  15};
  16
  17// global data - okay for a simple example like this
  18particle flakes[total_flakes]; 
  19particle lyingFlakes[total_flakes];
  20
  21// This function initalizes the particle flakes
  22void initalize_particle_flakes(void)
  23{
  24    int i;
  25    for (i=0;i<total_flakes;i++)
  26    {
  27        flakes[i].x=rand()%320; // 0-319 [x]
  28        flakes[i].y=rand()%200; // 0-199 [y]
  29        flakes[i].layer=rand()%total_layers;// [0-2] [layer]
  30    
  31    lyingFlakes[i].x = ceilf((i / 2.8125));
  32    lyingFlakes[i].y = 199;
  33    }
  34}
  35
  36void check_for_piling(ALLEGRO_DISPLAY *display, ALLEGRO_BITMAP *haufen) {
  37  for (int i=0;i<total_flakes;i++)
  38    {    
  39    ALLEGRO_COLOR particelColor = al_map_rgb(255,255,255);
  40    ALLEGRO_COLOR pixelColor = al_get_pixel(haufen,flakes[i].x, flakes[i].y);
  41
  42    if((particelColor.r == pixelColor.r) && (particelColor.g == pixelColor.g) && (particelColor.b == pixelColor.b)) {
  43      // if((flakes[i].y >= 199)) {
  44        al_set_target_bitmap(haufen);
  45        al_put_pixel(flakes[i].x, (flakes[i].y - 1), particelColor);
  46        al_set_target_bitmap(al_get_backbuffer(display));
  47        al_draw_bitmap(haufen, 0.0, 0.0, 0);
  48        al_flip_display();
  49      // }
  50    }
  51    }
  52}
  53
  54// This function draws all the particle flakes
  55void draw_particle_flakes(ALLEGRO_DISPLAY *display)
  56{
  57    int i;
  58  
  59  for (i=0;i<total_flakes;i++)
  60    {    
  61    al_put_pixel(flakes[i].x, flakes[i].y, al_map_rgb(255,255,255));
  62    }
  63}
  64 
  65// This updates the particle flakes
  66void update_particle_flakes(ALLEGRO_DISPLAY *display)
  67{
  68    int i;
  69
  70    for (i=0;i<total_flakes;i++)
  71    {
  72    ALLEGRO_COLOR pixelColor = al_get_pixel(al_get_backbuffer(display),flakes[i].x, flakes[i].y);
  73    ALLEGRO_COLOR particelColor = al_map_rgb(255,255,255);
  74
  75        // drop the particle down - depending on layer
  76        // [plus one - since layer zero would result 
  77        // in no motion otherwize]
  78        flakes[i].y+=flakes[i].layer+1;
  79 
  80        // check for wrap around
  81    if (flakes[i].y>199)
  82    {
  83        flakes[i].x=rand()%320;
  84        flakes[i].y=0;
  85        flakes[i].layer=rand()%total_layers;
  86    }
  87
  88        // new x position   
  89        flakes[i].x=(flakes[i].x+(2-rand()%5)) % 320;
  90    }
  91}
  92
  93void update_display(ALLEGRO_DISPLAY *display) {
  94    update_particle_flakes(display);
  95  al_clear_to_color(al_map_rgb(0,0,0));
  96  draw_particle_flakes(display);
  97  al_flip_display();
  98}
  99 
 100// main program
 101int main(int argc, char *argv[]) {         
 102            int i;
 103            
 104            al_init();        // init Allegro 
 105            al_install_keyboard();    // setup allegro keyboard
 106            
 107      ALLEGRO_DISPLAY *display = NULL;
 108      display = al_create_display(320, 200);
 109
 110      ALLEGRO_BITMAP *haufen = NULL;
 111      haufen = al_create_bitmap(320, 200);
 112
 113      ALLEGRO_EVENT_QUEUE *event_queue = NULL;
 114      event_queue = al_create_event_queue();
 115
 116      al_register_event_source(event_queue, al_get_display_event_source(display));
 117
 118      ALLEGRO_EVENT ev;
 119      ALLEGRO_TIMEOUT timeout;
 120      al_init_timeout(&timeout, 0.06);
 121
 122      bool got_event = al_wait_for_event_until(event_queue, &ev, &timeout);
 123
 124      ALLEGRO_COLOR white = al_map_rgb(255,255,255);
 125
 126            initalize_particle_flakes();      
 127            
 128      al_set_target_bitmap(haufen);
 129      for (i=0;i<total_flakes;i++) {
 130        al_put_pixel(lyingFlakes[i].x, lyingFlakes[i].y, al_map_rgb(255,255,255));
 131      }
 132      al_set_target_bitmap(al_get_backbuffer(display));
 133      al_draw_bitmap(haufen, 0.0, 0.0, 0);
 134      al_flip_display();
 135
 136      while (true) { 
 137          update_display(display);
 138          check_for_piling(display, haufen);
 139      };
 140 
 141            return 0;     
 142}

best regards and many thanks for any help !

djtschke

no-reply@allegro.cc (jmasterx) — Wed, 03 Aug 2011 19:41:33 +0000

Putting pixels is expensive in A5 and likely your bottleneck. Look into bitmap locking or blit your particle to a bitmap then draw that bitmap instead with al_hold_bitmap_drawing set to true.

no-reply@allegro.cc (djtschke) — Wed, 03 Aug 2011 19:48:53 +0000

I already looked into the al_lock_bitmap() function and experimented a bit. But it didn't really help anything. Also I must confess I didn't quite get the clue of how that function works.

best regards,

djtschke

no-reply@allegro.cc (jmasterx) — Wed, 03 Aug 2011 20:14:50 +0000

Then try the other method. create a new bitmap, set it as the target bitmap, draw your pattern, then set the target back to the back buffer, now instead of calls to al_draw_pixel, right before the for loop call:

al_hold_bitmap_drawing(true);

then in your for loop, draw the bitmap.
then after the for loop call:

al_hold_bitmap_drawing(false);

no-reply@allegro.cc (SiegeLord) — Wed, 03 Aug 2011 20:50:01 +0000

Try al_draw_prim with ALLEGRO_PRIM_POINT_LIST and a custom vertex declaration (see ex_prim example).

no-reply@allegro.cc (North~) — Thu, 04 Aug 2011 05:10:46 +0000

A bit off-topic but that's a horrible gap in the tutorial I see. It goes from basically the smallest possible allegro program to a slightly extensive particle snow tutorial.

no-reply@allegro.cc (weapon_S) — Thu, 04 Aug 2011 12:37:56 +0000

Very much off-topic:

Tutorial said:

I run my laptop at 60hz, but my PC at 120.

Yesterday I discovered my CRT monitor had a 120Hz mode
I didn't know of al_draw_prim. Interesting. How do you define colour when using NULL as a texture?

no-reply@allegro.cc (SiegeLord) — Thu, 04 Aug 2011 22:26:16 +0000

ALLEGRO_VERTEX has a color parameter. Custom vertex declarations also have a method to specify the color.

Question on increasing "render" speed