Tile based map and collision; getting stuck

Question

I'm trying to make my character move around a tile map with collisions. Everything works fine except for one thing. I show you a picture with the problem:

https://i.sstatic.net/ZWI7x.jpg

That is, when I reach a tile above then I can not move anywhere. If you come from the left, I can not move either up or down. If you reach the bottom, I can move to the left but not right. And when you reach the right I can move in any direction.

Honestly I have no idea what may be failing. I think it has to do with if (...), because if I change the order, the addresses where I can move change :/

Here I leave some code:

boolean collision = false;

if(Keyboard.isKeyDown(Keyboard.KEY_UP)) {
    for(int i = 0; i < map.GetNumLayers(); i++) {
        if(UpTile(map, i) > 128) {
            collision = true;
        }
    }

    if(!collision) AddPos(0.0f, -vel);
}
if(Keyboard.isKeyDown(Keyboard.KEY_LEFT)) {
    for(int i = 0; i < map.GetNumLayers(); i++) {
        if(LeftTile(map, i) > 128) {
            collision = true;
        }
    }

    if(!collision) AddPos(-vel, 0.0f);
}
if(Keyboard.isKeyDown(Keyboard.KEY_DOWN)) {
    for(int i = 0; i < map.GetNumLayers(); i++) {
        if(DownTile(map, i) > 128) {
            collision = true;
        }
    }

    if(!collision) AddPos(0.0f, vel);
}
if(Keyboard.isKeyDown(Keyboard.KEY_RIGHT)) {
    for(int i = 0; i < map.GetNumLayers(); i++) {
        if(RightTile(map, i) > 128) {
            collision = true;
        }
    }

    if(!collision) AddPos(vel, 0.0f);
}

public int UpTile(Map map, int layer) {
    return map.GetValue(layer, (int) (x/size), (int) (y/size));
}

public int LeftTile(Map map, int layer) {
    return map.GetValue(0, (int) (x/size), (int) (y/size));
}

public int DownTile(Map map, int layer) {
    return map.GetValue(layer, (int) (x/size), (int) (y/size + 1));
}

public int RightTile(Map map, int layer) {
    return map.GetValue(layer, (int) (x/size + 1), (int) (y/size));
}

public int GetValue(int layer, int x, int y) {
    return array[layer][y][x];
}

The map is an array with 3 componentes: [LAYER][Y][X]. So, in RightTile by example, with GetValue, I'm getting the value from the array in the position [layer][y/size][x/size + 1], x/size + 1 because I want to get the kind of tile that is to my right (same with the others). size = 64, that is the width and height of each tile.

Thanks >.<

Answer 1

The upper right of the shown screens is misleading, you are only prevented from moving right in that situation if you try to move down at the same time. The reason that trying to move in another direction can block your movement is that you don't reset you variable collision to false between checks, thus as soon as one direction has set it to true it will it will block the following move directions.

Take a visual glance at what points you are actually checking, the upper left corner of your character twice, the upper right, and the lower left. Seems like a strange pattern, right?

To get things working as you'd want them in a simple fashion I suggest you use an 8 points method, 2 points for each direction, positioned at the corners of your character, moved out at least as far as the maximum moving speed.

Left: Current test. Right: Suggested test.

Answer 2

I agree with Maik - debugging will help you here.

To do this you could walk to the top of the screen, then insert a breakpoint after:

if(Keyboard.isKeyDown(Keyboard.KEY_LEFT)) {

And then press left and follow your code through to see if it does what you think it does. My best bet is that there is a problem indexing the map array; you should verify that the coordinates that are accessed are the correct coordinates.

I did notice some things that could potentially be the cause:

You said the map is an array with three components: [LAYER][Y][X] but then your calls to GetValue index in another order: LAYER, X, Y (although I guess your GetValue function probably does switch those around).

Also I'm not sure why you are doing (x/size) in UpTile/DownTile/RightTile/LeftTile - if x is smaller than 64 (and is an int) you'll get 0.

Also, I presume:

public int LeftTile(Map map, int layer) {
    return map.GetValue(0, (int) (x/size), (int) (y/size));
}

should be:

public int LeftTile(Map map, int layer) {
    return map.GetValue(layer, (int) (x/size), (int) (y/size));
}