need help with simple effect

need help with simple effect

matt reynolds

Member #7,448

July 2006

i got this code from a hugi article and im trying to change it a little bit to make the snow pile up

1#include "allegro.h"   
2 
3using namespace std;
4 
5// data structures for snow flaxes = very simple
6const int total_flakes=900;
7const int total_layers=3;
8 
9struct particle
10{
11    int x,y;
12    int layer;
13};
14 
15// global data - okay for a simple example like this
16particle flakes[total_flakes];   
17 
18// This function initalizes the particle flakes
19void initalize_particle_flakes(void)
20{
21    int i;
22    for (i=0;i<total_flakes;i++)
23    {
24        flakes<i>.x=rand()%320; // 0-319 [x]
25        flakes<i>.y=rand()%200; // 0-199 [y]
26        flakes<i>.layer=rand()%total_layers;// [0-2] [layer]
27    }
28}
29 
30// This function draws all the particle flakes
31void draw_particle_flakes(void)
32{
33    int i;
34    for (i=0;i<total_flakes;i++)
35    {
36        // note - we are drawing according to the color scale
37        _putpixel(screen, flakes<i>.x, flakes<i>.y, 
38                  flakes<i>.layer*5+20);
39    }
40}
41 
42// This updates the particle flakes
43void update_particle_flakes(void)
44{
45    int i;
46    for (i=0;i<total_flakes;i++)
47    {
48        // drop the particle down - depending on layer
49        // [plus one - since layer zero would result 
50        // in no motion otherwize]
51        flakes<i>.y+=flakes<i>.layer+1;
52 
53        // check for wrap around
54        if (flakes<i>.y>199)
55        {
56                flakes<i>.x=rand()%320;
57                flakes<i>.y=0;
58                flakes<i>.layer=rand()%total_layers;
59        }
60 
61        // new x position        
62        flakes<i>.x=(flakes<i>.x+(2-rand()%5)) % 320;   
63 
64    }
65}
66 
67// main program
68int main(int argc, char *argv[]) {         
69            int i;
70            
71            allegro_init();        // init Allegro 
72            install_keyboard();    // setup allegro keyboard
73            
74            set_color_depth(8) ;   // 8 bit colour
75            if (set_gfx_mode(GFX_AUTODETECT_FULLSCREEN, 
76                320, 200, 0, 0)<0)
77            {
78                set_gfx_mode(GFX_TEXT, 0, 0, 0, 0);  
79                allegro_message("Failure to init video mode!\n%s\n", 
80                                 allegro_error);
81            }
82            initalize_particle_flakes();      
83            
84            while ((!key[KEY_ESC])&&(!key[KEY_SPACE])) {
85                  update_particle_flakes();
86          vsync(); // you might want to add another vsynch; 
87                   // depending how fast
88          vsync();     //things are moving on your box
89          vsync();
90          
91          clear_bitmap(screen);   
92          draw_particle_flakes();
93    };
94 
95            return 0;     
96}     
97END_OF_MAIN();

the only thing i have thought of is maybe something like this but i tryed it and it just made some dynamic snow on the bottom

        int pixx,xs,xpile,ypile
        pixx = 0;
        pixx = _getpixel(screen, xs=rand()%xpile, ypile);
        if (pixx < 1)
       _putpixel(screen, xs, ypile, layers=rand()%3*5+20);

i am a newbie coder and a newbie to allegro but any advice would be great!

anto80

Member #3,230

February 2003

What do you want to do? particles(like fireworks?)?

[edit] if so, this thread may help you.
http://www.allegro.cc/forums/thread/415131

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CursedTyrant

Member #7,080

April 2006

1#include "allegro.h"   
2 
3using namespace std;
4 
5// data structures for snow flaxes = very simple
6const int total_flakes=900;
7const int total_layers=3;
8 
9struct particle
10{
11    float x,y;
12    int layer;
13};
14 
15BITMAP *buffer;
16 
17volatile int Counter;
18void IncreaseCounter() { Counter++; }
19 
20// global data - okay for a simple example like this
21particle flakes[total_flakes];   
22 
23// This function initalizes the particle flakes
24void initalize_particle_flakes(void)
25{
26    int i;
27    for (i=0;i<total_flakes;i++)
28    {
29        flakes<i>.x=rand()%320; // 0-319 [x]
30        flakes<i>.y=rand()%200; // 0-199 [y]
31        flakes<i>.layer=rand()%total_layers;// [0-2] [layer]
32    }
33}
34 
35// This function draws all the particle flakes
36void draw_particle_flakes(void)
37{
38    int i;
39    for (i=0;i<total_flakes;i++)
40    {
41        // note - we are drawing according to the color scale
42        _putpixel(buffer, int(flakes<i>.x), int(flakes<i>.y), 
43                  flakes<i>.layer*5+20);
44    }
45}
46 
47// This updates the particle flakes
48void update_particle_flakes(void)
49{
50    int i;
51    for (i=0;i<total_flakes;i++)
52    {
53        // check for wrap around
54        if (flakes<i>.y<SCREEN_H-2 && _getpixel(buffer, int(flakes<i>.x), int(flakes<i>.y+1))!=flakes<i>.layer*5+20)
55        {
56  if (flakes<i>.y>199)
57  {
58            flakes<i>.x=rand()%320;
59            flakes<i>.y=0;
60            flakes<i>.layer=rand()%total_layers;
61  }
62  flakes<i>.x=(int(flakes<i>.x)+(2-rand()%5)) % 320;
63  flakes<i>.y+=flakes<i>.layer*0.1+0.5;
64        }
65 
66    }
67}
68 
69// main program
70int main(int argc, char *argv[]) {         
71            int i;
72            
73            allegro_init();        // init Allegro 
74            install_keyboard();    // setup allegro keyboard
75            install_timer();
76            
77      LOCK_VARIABLE(Counter);
78      LOCK_FUNCTION(IncreaseCounter);
79      install_int_ex(IncreaseCounter, BPS_TO_TIMER(60));
80            
81            set_color_depth(8) ;   // 8 bit colour
82            if (set_gfx_mode(GFX_AUTODETECT_WINDOWED, 
83                320, 200, 0, 0)<0)
84            {
85                set_gfx_mode(GFX_TEXT, 0, 0, 0, 0);  
86                allegro_message("Failure to init video mode!\n%s\n", 
87                                 allegro_error);
88            }
89            initalize_particle_flakes();      
90            
91      buffer = create_bitmap(SCREEN_W, SCREEN_H);
92      clear(buffer);
93            
94            while ((!key[KEY_ESC])&&(!key[KEY_SPACE])) {
95      while (Counter>0)
96      {
97    update_particle_flakes();
98    Counter--;
99      }
100            clear(buffer);
101            draw_particle_flakes();
102      blit(buffer, screen, 0, 0, 0, 0, SCREEN_W, SCREEN_H);
103    };
104 
105            return 0;     
106}     
107END_OF_MAIN();

That should do it. The particles pile up and lie on the bottom of the screen.

- Use timers and floats instead of vsync
- Use that double buffer, don't draw directly to the screen, makes things flicker

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matt reynolds

Member #7,448

July 2006

thanks for the help...
wow you cleaned that code up nicley its so much more understandable like that
there is a few new functions and etc you introduced in there i will have to lookup but
for the most part i understand it