need help with simple effect
matt reynolds

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

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

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

CursedTyrant
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

matt reynolds

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

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