java movement in a 2d array

Question

In the game i'm building, I have made a basic collision detection system.

My current method is explained below:

I workout where the player will be in the next step of the game:

double checkforx = x+vx;
double checkfory = y+vy;

I then check for a collision with blocks (1) in mapArray.

public static Boolean checkForMapCollisions(double character_x,double character_y){

    //First find our position in the map so we can check for things...
    int map_x = (int) Math.round((character_x-10)/20);
    int map_y = (int) Math.round((character_y-10)/20);

    //Now find out where our bottom corner is on the map
    int map_ex = (int) Math.round((character_x+10)/20);
    int map_ey = (int) Math.round((character_y+10)/20);

    //Now check if there's anything in the way of our character being there...

    try{
        for(int y = map_y; y <= map_ey; y++){
            for(int x = map_x; x <= map_ex; x++){
                if (levelArray[y][x] == 1){
                    return true;
                }
            }
        }
    }catch (Exception e){
        System.out.println("Player outside the map");
    }
    return false;
}

If true is returned {nothing}

If false is returned {Player physics}

I need the player to be able to land on a block and then be able to walk around but I cannot find and adequate tutorial for this.

Can someone give me an idea on how to run my collision detection and/or movement?

William Morrison · Accepted Answer · 2013-08-07 00:31:05Z

There are 2 parts to this question. Collision detection, meaning determining whether a volume is touching or intersecting another volume. The second is collision response. Collision response is the physics portion.

I'll cover collision detection here as that's primarily what you asked about.

Ddefine a class for the map like so:

int emptyTile = 0;
//this assumes level is not a ragged array.
public boolean inBounds(int x, int y){
    return x>-1 && y>-1 && x<levelArray[0].length && y<levelArray.length;
}

public boolean checkForCollisions(Rectangle rectangle){
    boolean wasCollision = false;
    for(int x=0;x<rectangle.width && !wasCollision;x++){
        int x2 = x+rectangle.x;
        for(int y=0;y<rectangle.height && !wasCollision;y++){
             int y2 = y+rectangle.y;
             if(inBounds(x2,y2) && levelArray[y2][x2] != emptyTile){
                 //collision, notify listeners.
                 wasCollision=true;
             }
        }
    }
}

Do not make your methods static. You probably want more than one instance of a level right? Static is for when you need to share state which remains constant across multiple instances of a class. Level data will surely not remain constant for every level.

Instead of passing in a coordinate, try passing in an entire rectangle. This rectangle will be the bounding box of your character (the bounding box is also sometimes referred to as AABB, which means Axis-aligned bounding box, just FYI in case you're reading tutorials online for this sort of thing.) Let your Sprite class decide what its bounding rectangle is, that's not the map class's responsibility. All the map should be used for is maybe rendering, and whether a rectangle is overlapping tiles which are not empty.

Quillion · Accepted Answer · 2013-08-06 23:45:08Z

0

I am sorry for a very shitty explanation but here is my github code and it will help better.

https://github.com/Quillion/Engine

Just to explain what I do. I have character object (https://github.com/Quillion/Engine/blob/master/QMControls.java) and it has vectors and a boolean called standing. Every time boolean standing is false. Then we pass it to the engine to check for collision, if collision happens then standing is true and y vector is 0. As to x vector whenever you press any arrow keys you make the xvector of the object to whatever value you want. And in the update loop you displace the given box by the amount of speed.

answered Aug 6, 2013 at 23:45

Quillion

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