C++ Platformer Collision

Question

This is very simple, but I have spent nearly 6 months messing with this and it is always messed up.

This is a tile platformer, everything is "normal", x and y correspond to tile. Tiles are 32 x 32 pixels.

// Get all tile numbers, top left, top right, bottom left, bottom right
int X = 63; // and in this, say the player is moving right
int Y = 50;
int Width = 33; // This is the problem, if it is < 32, the collisions are all over the place, in the open, where there shouldn't be.
int Height = 50;


int tile_x = floor( (double) X/32);
int tile_y = floor( (double) Y/32);
int tile_x2 = floor( (double) (X + Width)/ 32);
int tile_y2 = floor( (double) (Y + Height)/ 32);
bool open = true;

// This is meant to catch cases where width < 32
if (tile_x == tile_x2) {
    if (IsOpenPt(tile_x, tile_y)) { return true; }
}

// loop through tiles
for (int y = tile_y; y < tile_y2; y++) {

    for (int x = tile_x; x < tile_x2; x++) {

        // this spot is not open
        if (!IsOpenPt(x,y)) { open = false; }

    }
}

return open;

This works if the width is greater than 32, but if it anything less, everything becomes random open point/ not.

See anything wrong with my formula? I have exhausted searches, nothing. Once again I emphasize, the entire project, I have been trying to get this part to work. I have literally a 100 page notebook of attempts at visualizing and grids to put it on paper.

Answer 1

I think you need some documentation about collisions. It seems you want to check the collision between 2 hitbox on a 2D game:

if (rect1.x < rect2.x + rect2.width &&
   rect1.x + rect1.width > rect2.x &&
   rect1.y < rect2.y + rect2.height &&
   rect1.height + rect1.y > rect2.y) {
    // collision detected!
}

But you're trying to make a pixel perfect collision, which is needed only when you have check a collision with this code.

This article seems to make a good summarize of the topic.

Answer 2

Your issue seems to be that you are only checking a single tile if your player is 32 or less pixels wide. That obviously does not work, because your player is taller than one tile. Hence, you need to remove the first easy-oit as it breaks the detection, and simply just rely on the looping method.

Answer 3

It's not clear what you are trying to achieve, but changing the < operators to <= might be a step in the right direction.