Debugging movement/collision code in 2d tile game

[digdugdiggy]

Hello, I'm working on a top down 2d game and am having some problems with collision detection. Here is a basic screenshot.



My issue involves buggy movement. If I spam movement keys near a wall, I can pass through and get stuck. I think my problem may be related to multiple threads, but I am not sure.

I have a text file grid of integers read in for collision, 1 = not passable, 0 = passable. My checkCollision function checks the proposed new player position for a collision, and disallows that movement if there is a tile.

I use a overridden Keymanager classhttp://pastebin.java-gaming.org/b9854254086 to alter Player's public variables UP, DOWN, LEFT, RIGHT to transfer keyboard to game logic.

Here is the player tick class:

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public class Player { **SNIP SNIP** public void tick() {         if (moving) {             updatePlayerPosition();         }         if (sprinting) {             moveSpeed = SPRINT; // 16         } else {             moveSpeed = WALK; // 8         }         if (!moving) {             if (up) {                 moveUp();             }             if (down) {                 moveDown();             }             if (right) {                 moveRight();             }             if (left) {                 moveLeft();             }         }

Here I update the player movement if they are still in the process of moving from one tile to another. http://pastebin.java-gaming.org/9854530468e

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private void updatePlayerPosition() {                 switch (facing) {             case "north":                 if (!detectCollision(tileX, tileY - 1)) {                     northAnimator.update(System.currentTimeMillis());                     y -= moveSpeed;                     if (y % 32 == 0) {                         moving = false;                         tileY = (int) pixelsToTileY(y);                     }                 }                 break;             case "south": *SNIPSNIP*         }     }

This simply changes facing direction, sets moving to true, and lets the above method handle the rest. http://pastebin.java-gaming.org/4506e684f89

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private void moveUp() { // move player up         // if not facing north, make facing north         if (!facing.equals("north")) {             facing = "north";         } else {             // else, detect collision in the direction                         if (!detectCollision(tileX, tileY - 1)) {                 moving = true;             }         }     }

Somewhere in here there is a bug going on. I know the detectcollision method is working properly as I debugged it with println's. It seems that sometimes, while I am actively "Moving", my direction can change and place me in a wall. Note that this code has double collision checking, I tried with one and it simply let me into impassable walls, with two checks i actually get stuck in the wall and cant move at all.

Can anyone help me out here. Is there a simpler way of getting animated tile movement?

[HeroesGraveDev]

I think my problem may be related to multiple threads, but I am not sure.

You shouldn't need multithreading for a simple 2D game.

Multithreading is a nightmare and introduces lots of problems. It's probably best you don't use it unless you're absolutely certain you need it.

[opiop65]

You are most likely dealing with rounding issues with the player's position when checking against the tile coordinates on the map.

Games published by our own members! Check 'em out!

[digdugdiggy]

I'm doing stuff like this to start up my game, not sure if this is multithreading or just one thread getting started up?

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public class TileGame extends Canvas implements Runnable { public synchronized void start() {         if (running) {             return;         }         running = true;         gameThread = new Thread(this);         gameThread.start();} @Override     public void run() { *snipsnip*     }

On second thought, I dont think it is multithreaded. I kinda followed a tutorial for the basic game loop stuff, and I think all this just starts up one thread for the game.

[trollwarrior1]

Here you go, a full proof tutorial on collision within tiles.

http://www.java-gaming.org/topics/2d-collision-detection/31488/view.html

[digdugdiggy]

Here you go, a full proof tutorial on collision within tiles.

http://www.java-gaming.org/topics/2d-collision-detection/31488/view.html

Thank you, I will review this.

[opiop65]

Is that theChernoProject? If it is, I have to say he's an ok programmer, but one thing that has always bugged me is his use of threads. You don't need to manually create a thread just to start a game. There is absolutely (as far as I know) no advantage to it, and it really isn't a good design.

[trollwarrior1]

You need to create a separate thread for your game when you're using JFrame. If you don't, you will have problems with JFrame.

[digdugdiggy]

You need to create a separate thread for your game when you're using JFrame. If you don't, you will have problems with JFrame.

The great tutorial maker arrives! I was just reading your tutorial linked above! Thanks for it, I'm just fiddling with the LWJGL keyboard stuff there.

Also, how would I go about making a seperate thread for my jframe? I have no experience with threads really.
Here is my main, which pretty much just makes a frame and launches it. I assume I would have to modify this?

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public static void main(String[] args) {        TileGame game = new TileGame();         game.setPreferredSize(new Dimension(TileGame.WIDTH * TileGame.SCALE, TileGame.HEIGHT * TileGame.SCALE));         game.setMaximumSize(new Dimension(TileGame.WIDTH * TileGame.SCALE, TileGame.HEIGHT * TileGame.SCALE));         game.setMinimumSize(new Dimension(TileGame.WIDTH * TileGame.SCALE, TileGame.HEIGHT * TileGame.SCALE));         JFrame frame = new JFrame("Autumn Cornucopia");         frame.setSize(TileGame.WIDTH * TileGame.SCALE, TileGame.HEIGHT * TileGame.SCALE);         frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);         frame.setResizable(false);         frame.add(game);         frame.setLocationRelativeTo(null);         frame.requestFocus();         frame.toFront();         frame.setVisible(true);         //gsm = new GameStateManager();         //gsm.start();         game.start();     }

[digdugdiggy]

Ok, regarding the initial problem:

Thanks to the tutorial, I figured it out. In the end I ran into a simple semantics problem.
The code above references a "CanMove" method which checks a tile to see if the player can move there, while my collision layer was using the term "DetectCollision".

It took me a bit to figure out that (CanMove = true) != (DetectCollision = true). One says "yes you can move there", the other says "yes there is a collision".

Now I am trying to alter this new movement method so I can have similar movement as before. IE: Press button,ignore input,  move player image a few pixels, repeat for X ticks until centered on a tile, allow input again.

Also! I noticed a slight bug in the tutorial code, which was mentioned. Even if the player wasnt moving, it continued to call the CanMove functions a total of 10+ times every tick.