# AABB vs TileMap collision response

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Hi everyone!
I'm making a 2d tilemap game..and I have problems with aabb vs tilemap collision response..here's how I do it:
void handle_player_world_collision(Player* player,TileMap* map)
{
int topleft_xtile=map->xworld_to_map(player->pos.x);
int topleft_ytile=map->yworld_to_map(player->pos.y);
int bottright_xtile=map->xworld_to_map(player->pos.x+player->aabb.w);
int bottright_ytile=map->yworld_to_map(player->pos.y+player->aabb.h);

//we loop through all the tiles that the player's aabb touch
for(int i=topleft_xtile;i<bottright_xtile;i++)
{
for(int j=topleft_ytile;j<bottright_ytile;j++)
{
//here we test for map coordinates (i,j) validity...
//...
///////
if(map->getTile(i,j)->is(Tile::SOLID))
{
if(player->vel.x<=0 && player->vel.y<=0)
{//we are trying to move left_top;calculate the overlap according to each axis
//and resolve collision where the overlap is minimal
float xoverlap=(i+1)*map->tile_width-player->pos.x;
float yoverlap=(j+1)*map->tile_height-player->pos.y;
if(xoverlap<yoverlap)
{
player->pos.x=(i+1)*map->tile_width;
player->vel.x=0;
}
else
{
player->pos.y=(j+1)*map->tile_height;
player->vel.y=0;
}
}
//here you the same as above
//detect what's the movement direction that led o this
//collision.
//resolve collision by changing the player position to
//be adjacent to the tile in the direction where the
//overlap was minimal!
}
}
}
}

I have problems in detecting the collision when I move diagonally;and sometimes even horizontally!
Am I doing it right?of course not...
I want also to detect the side of the collision of two AABB..
Can Anyone show me how to do it? Edited by lukadev0

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int topleft_xtile=map->xworld_to_map(player->pos.x);
int topleft_ytile=map->yworld_to_map(player->pos.y);
int bottright_xtile=map->xworld_to_map(player->pos.x+player->aabb.w);
int bottright_ytile=map->yworld_to_map(player->pos.y+player->aabb.h);

shouldn't that be player_x - aabb_w / 2, player_y - aabb_h / 2 ?

you want the BBox centered on the player, not the UL corner of the BBox at the player's center.

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top left is px-w/2 py-h/2

bottom right is px+w/2, py+h/2

or

bottom right x = top left x + w (or w+1)

bottom right y = top left y + h (or h+1)

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Hi,

The AABB is represented using the UL corner (the player pos) and the (width and height of the aabb)..I know this have to change so the aabb could be centred on the player in order to have some fair gameplay!

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