Need help in collision Detecting: -using map[MAPW*MAPH] array. how would you do collision detection? list any examples plz! thank you [Edited by - Deamonslayer on April 23, 2006 11:52:06 PM]

k, sorry about that lol, not usto forum listing. okay heres more info:
#define MODE GFX_AUTODETECT_WINDOWED
#define WIDTH 640
#define HEIGHT 480
#define MAXSPEED 5
#define TILEW 32
#define TILEH 32

#define COLS 20
#define MAP_ACROSS 31
#define MAP_DOWN 33
#define MAPW MAP_ACROSS * TILEW
#define MAPH MAP_DOWN * TILEH
#define SCROLLW 480
#define SCROLLH 390

typedef struct SPRITE
{
int dir, alive;
int x,y;
int width, height;
int xspeed, yspeed;
int xdelay,ydelay;
int xcount,ycount;
int curframe, maxframe, animdir;
int framecount, framedelay;
}SPRITE;

SPRITE myhero;
SPRITE *hero;

BITMAP *hero_bmp[5][4];


//game map
extern int map[];

//double buffer
BITMAP *buffer;

//bitmap containing tiles
BITMAP *tiles;

//Virtual background buffer
BITMAP *scroll;


//vars
int gameover;
int score;
int scrollx,scrolly;
int startx,starty;
int tilex, tiley,n;

int map[MAPW*MAPH] = {

23, 21, 21, 21, 21, 21, 21, 21, 21, 21, 22, 1, 1, 1, 1, 1, 1, 23, 21, 21, 21, 21, 21, 21, 21, 22, 1, 1, 1, 1 ,1,
22, 89, 89, 89, 89, 89, 89, 89, 89, 89, 22, 1, 1, 1, 1, 1, 1, 22, 95, 95, 95, 95, 95, 95, 95, 22, 1, 1, 1, 1, 1,
//ETC
};

//Tile Loading Snippet
///How tiles are loaded to screen
tiles = load_bitmap("tiles.bmp",NULL);
for(tiley=0;tiley < scroll->h; tiley+=TILEH)
{
for(tilex=0;tilex < scroll->w; tilex+=TILEW)
{
blit(grabframe(tiles, TILEW, TILEH, 0, 0, COLS, map[n++]), scroll, 0, 0, tilex, tiley, TILEW, TILEH);
}
}

//Movement Snippet
void forward()
{
hero->curframe++;
hero->dir=0;
if(scrolly >= scroll->h - SCROLLH && hero->y > 285)
{
hero->y-=5;
}
else if(scrolly <= 0)
{
hero->y-=5;
}
else
{
scrolly -=5;
}

I am using the Allegro lib.

Okay so a rough overview is its a scrolling game, with an animating hero.
my first general idea was to figure out what tile am i even stepping on.
by: tile=map[((scrollx+hero->x)/TILEW)*((scrolly+hero->y)/TILEH)];
but this doesnt even work. i spit this info by texout and end up not telling me the rite tile i am on.


I hope this helps! tell me what else u need to know to help if i missed something.

Collision done by:

tile = map[Playery * Cols + playerx]

collision
if(tile == wall)
player != move;

I answered on my own WOOT!
Thanks all

Quote:Instead of Map[w * h], you should consider using something like:

struct {
int ground;
int fringe;
int wall;
} Map[MAX_HEIGHT][MAX_WIDTH];

This will give you a multilayer map so you can draw ground (like grass, water), fringe above the ground (rocks, a road, flowers), and walls, which will be blocking your character's movement.

Off topic but I thought it useful...

Actually, a few years ago I was wondering how to do all of this stuff myself. After hours of searching on-line I came accross articles explaining that C does not have support for "true" multidimensional arrays. This made me nuts. Anyway, the single dimensional array approach (IMHO) is much easier to implement when it comes to dynamic arrays.... but moving on...

The way the OP is doing it is actually how this is done internally for a multi dimensional array and in the future when dynamic multi-dimensional arrays may be needed, it is much simpler to create single dimensional arrays the same size as w*h or even w*h*layers and do the math internally as opposed to creating arrays of arrays.



Now, the code for the array[x][y] gets more confusing as you add more dimensions but the single dimensional array is generally the same with the exception of a little more math to find which part of the array you want. That being said, it is undeniably easier if you have a static sized map and can use array[x][y]. The main drawback being lack of flexibility.


*** at the OP ***
Congrats on figuring out your own problem.