Sprite collision with tile map - c++

Question

So, I'm trying to build my own game engine and my first project is creating a pacman clone. I've worked out how to create the tilemap and move pacman around on it. But I've having issues creating a collision detector with the tilemap. Particularly the issue is that the collision detects fine for any tiles north of the current location, however it thinks the tile below the current location is actually 1 tile larger than normal. And 0 collision exists for tiles east and west of the current location. I'm confused because the collision works for the north tile... but I'm using the same logic for the other directions and it's not working.
The logic I am using is that 'okay' tiles to move into are value 0. Any other tile is not able for movement.
Here is the code I'm using for the actual wall collision:
//checks for a sprite colliding with a wall tile
//direction refers to 1=North, 2=South, 3=West, 4=East
bool Wall_Collision(SPRITE sprite, int direction)
{
//grab center of sprite
Posx = sprite.x + Sprite_Radius;
Posy = sprite.y + Sprite_Radius;
//create rectangle for the sprite
RECT spriteRect;
spriteRect.left = (long)sprite.x;
spriteRect.top = (long)sprite.y;
spriteRect.right = (long)sprite.x + sprite.width * sprite.scaling;
spriteRect.bottom = (long)sprite.y + sprite.height * sprite.scaling;
//recover North tile info
int N_posx, N_posy;
int N_tilex, N_tiley;
int N_tilevalue;
N_posx = Posx / TILEWIDTH;
N_posy = (Posy - TILEHEIGHT) / TILEHEIGHT;
N_tilex = N_posx * TILEWIDTH;
N_tiley = N_posy * TILEHEIGHT;
N_tilevalue = MAPDATA[(N_posy * MAPWIDTH + N_posx)];
//create rectangle for tile North of sprite center
RECT northRect;
northRect.left = N_tilex;
northRect.top = N_tiley;
northRect.right = N_tilex + TILEWIDTH;
northRect.bottom = N_tiley + TILEHEIGHT;
//recover South tile info
int S_posx, S_posy;
int S_tilex, S_tiley;
int S_tilevalue;
S_posx = Posx / TILEWIDTH;
S_posy = (Posy + TILEHEIGHT) / TILEHEIGHT;
S_tilex = S_posx * TILEWIDTH;
S_tiley = S_posy * TILEHEIGHT;
S_tilevalue = MAPDATA[(S_posy * MAPWIDTH + S_posx)];
//create rectangle for tile South of sprite center
RECT southRect;
southRect.left = S_tilex;
southRect.top = S_tiley;
southRect.right = S_tilex + TILEWIDTH;
southRect.bottom = S_tiley + TILEHEIGHT;
//recover West tile info
int W_posx, W_posy;
int W_tilex, W_tiley;
int W_tilevalue;
W_posx = (Posx - TILEWIDTH) / TILEWIDTH;
W_posy = Posy / TILEHEIGHT;
W_tilex = W_posx * TILEWIDTH;
W_tiley = W_posy * TILEHEIGHT;
W_tilevalue = MAPDATA[(W_posy * MAPWIDTH + W_posx)];
//create rectangle for tile West of sprite center
RECT westRect;
westRect.left = W_tilex;
westRect.top = W_tiley;
westRect.right = W_tilex + TILEWIDTH;
westRect.bottom = W_tiley + TILEHEIGHT;
//recover East tile info
int E_posx, E_posy;
int E_tilex, E_tiley;
int E_tilevalue;
E_posx = (Posx + TILEWIDTH) / TILEWIDTH;
E_posy = Posy / TILEHEIGHT;
E_tilex = E_posx * TILEWIDTH;
E_tiley = E_posy * TILEHEIGHT;
E_tilevalue = MAPDATA[(E_posy * MAPWIDTH + E_posx)];
//create rectangle for tile East of sprite center
RECT eastRect;
eastRect.left = E_tilex;
eastRect.top = E_tiley;
eastRect.right = E_tilex + TILEWIDTH;
eastRect.bottom = E_tiley + TILEHEIGHT;
RECT dest; //ignored
//check North collision
if (direction == 1 && N_tilevalue != 0)
{
return IntersectRect(&dest, &spriteRect, &northRect);
}
else return false;
//check South collision
if (direction == 2 && S_tilevalue != 0)
{
return IntersectRect(&dest, &spriteRect, &southRect);
}
else return false;
//check West collision
if (direction == 3 && W_tilevalue != 0)
{
return IntersectRect(&dest, &spriteRect, &westRect);
}
else return false;
//check East collision
if (direction == 4 && E_tilevalue != 0)
{
return IntersectRect(&dest, &spriteRect, &eastRect);
}
else return false;
}
And then the context I'm using the function to move the player sprite:
void MovePacman()
{
if (Wall_Collision(pacman, 1))
{
pacman.y -= pacman.vely;
pacman.vely = 0.0f;
}
else
{
if (Key_Down(DIK_UP))
{
pacman.vely = -0.2f;
pacman.velx = 0.0f;
}
}
if (Wall_Collision(pacman, 2))
{
pacman.y -= pacman.vely;
pacman.vely = 0.0f;
}
else
{
if (Key_Down(DIK_DOWN))
{
pacman.vely = 0.2f;
pacman.velx = 0.0f;
}
}
if (Wall_Collision(pacman, 3))
{
pacman.x -= pacman.velx;
pacman.velx = 0.0f;
}
else
{
if (Key_Down(DIK_LEFT))
{
pacman.velx = -0.2f;
pacman.vely = 0.0f;
}
}
if (Wall_Collision(pacman, 4))
{
pacman.x -= pacman.velx;
pacman.velx = 0.0f;
}
else
{
if (Key_Down(DIK_RIGHT))
{
pacman.velx = 0.2f;
pacman.vely = 0.0f;
}
else;
}
if (pacman.vely < 0)
Sprite_Animate(pacman.frame, pacman.startframe, 18, 4, pacman.starttime, 250);
else if (pacman.vely > 0)
Sprite_Animate(pacman.frame, pacman.startframe, 16, 2, pacman.starttime, 250);
else if (pacman.velx < 0)
Sprite_Animate(pacman.frame, pacman.startframe, 17, 3, pacman.starttime, 250);
else if (pacman.velx > 0)
Sprite_Animate(pacman.frame, pacman.startframe, 15, 1, pacman.starttime, 250);
pacman.y += pacman.vely;
pacman.x += pacman.velx;
}
trust that I've defined everything that is not pasted and linked headers correctly. Any ideas where I'm going wrong?

Answer 1

You're only checking for collisions in one case:
//check North collision
if (direction == 1 && N_tilevalue != 0)
{
return IntersectRect(&dest, &spriteRect, &northRect);
}
else return false; // <--- this
//check South collision
if (direction == 2 && S_tilevalue != 0)
{
return IntersectRect(&dest, &spriteRect, &southRect);
}
else return false; // <--- and this, etc...
See the line highlighted above. If it doesn't test for a North collision (i.e. if direction isn't 1 or N_tilevalue is 0) then the function returns at that point in all other cases. It can never go on to do the other collision checks.