I'm currently working on a tile collision system for an RPG style game and it mostly working except for some inconsistency with rectangle intersection.
protected void tileCollision()
{
AnimatedSprite player = findPlayer();
for(int i = 0; i < _sprites.size(); i++)
{
AnimatedSprite spr = _sprites.get(i);
for(int j = 0; j < tileWithinRange.length; j++)
{
Tile tile = tileWithinRange[j];
if(tile != null)
{
if(tile.getBounds().intersects(player.getBounds()))
{
player.setCollided(true);
tileCollision(player, tile, -1, -1);
} else
{
player.setCollided(false);
}
}
}
}
}
When I first collide with a tile upon launching the game, it always returns true, but if I move along a column of tiles, I start getting false returns and then after a while I only get false returns.
Here is an image of the player intersecting with a tile
There is an obvious intersection here, yet in this scenario, the variable collided returned false.
What is going wrong that the intersection isn't always registering?`
There is too little info here to really know what's happening, but something looks fishy here:
if(tile.getBounds().intersects(player.getBounds()))
{
player.setCollided(true);
tileCollision(player, tile, -1, -1);
} else
{
player.setCollided(false);
}
Since you are checking multiple tiles against the player in a loop, what if the player collides with the first tile, but doesn't collide with the second tile? You'd end up calling player.setCollided(false); even though he collided with a former tile, overwriting that true collision state with a false one. That might explain the behavior you're getting where you're getting only false returns after a while (perhaps because of the order in which you are checking the tiles makes it so you keep overwriting true states with false states).
I'm not sure if that's desirable or not to have these kinds of side effects, but it is a bit confusing at the very least to have this kind of collision state first being turned on and then overwritten with off within the same loop. If that's undesirable behavior, perhaps what you're after needs you to break out of the loop if a collision occurs. Or perhaps what you want is something more like this:
player.setCollided(false);
for(int j = 0; j < tileWithinRange.length; j++)
{
Tile tile = tileWithinRange[j];
if(tile != null && tile.getBounds().intersects(player.getBounds()))
{
player.setCollided(true);
tileCollision(player, tile, -1, -1);
}
}
}
Or maybe your bounds/intersection function is genuinely malfunctioning -- it's too hard to tell with so little code/info (we don't know how these are implemented).
It's good to be able to isolate your code and learn how to construct test cases to test out individual functions in little pieces independently. You want to eliminate suspects through a process of elimination with a testing procedure that allows you to figure out, "Okay, this part works perfectly in every case, let's move on to the next thing." Otherwise it becomes a guessing game trying to figure out what went wrong. One of the easiest ways to lose a time of time/productivity in development is to write a bunch of code first and then try to narrow down what went wrong in hindsight, instead of testing each little babystep. Mistakes get more expensive the later you discover them and the more suspects you have to go through in an investigation.
I ended up rewriting the method into a boolean which made it return true when colliding and false when not. Here is the new code.
public boolean tileCollision() {
AnimatedSprite player = findPlayer();
for(int j = 0; j < tileWithinRange.length; j++) {
Tile tile = tileWithinRange[j];
if(tile != null) {
if(tile.getTileBounds().intersects(player.getBounds()) ) {
return true;
}
}
}
return false;
}
Related
I am making a chess game and so far everything is good and I am writing the rules of each piece now. The problem is that a for loop is acting oddly. Its for the bishop so x is going down and y is going up. At this point it acts oddly whenever I try to add the point to a possible move
for (int i = 0; i < 8; i++) {
Point newLoc = new Point(x-i, y+i);
if(team.equals("white")) {
if(containsPiece(newLoc)) {
if(ChessBoard.black.containsKey(newLoc)) {
possibilities.put(newLoc, rating);
break;
}
else {
break;
}
} else
possibilities.put(newLoc, rating);
}
containsPiece() is working just fine and possibilities is the HashMap I am storing the possible moves in.
The way I see it it should be working perfect because if the tile at newLoc is white it shouldn't add it to the possible moves and stop getting any moves after it in that direction. Does anyone see why it seems to abandon all the previous possible moves added to possibilities
i should start in 1, not 0, since when i==0, newLoc is the position of the bishop ((x-0,y+0)), so you break from the loop, since the bishop is a white tile.
This function should check if the explosion hit a box and should be canceled on the first box it hits.
For example bsp.getBomb().getStrength() is currently 2, when a box is hit i=3, but the loop is executed one more time even if the condition isn't met, why is that?
public void detectBomb(BombSpritePair bsp) {
for(int i = 0; i <= bsp.getBomb().getStrength(); i++) {
if(bd.detect(bsp.getBomb().getX(), bsp.getBomb().getY()+i)) {
Sprite sprite = new Sprite(new Texture("gras.png"));
sprite.setPosition(bsp.getBomb().getX()*16, (bsp.getBomb().getY()+i)*16);
// i = bsp.getBomb().getStrength()+1;
sprites.add(sprite);
System.out.println("RIP"+i);
System.out.println(bsp.getBomb().getStrength());
break;
}
}
}
Try adding break to the loop:
public void detectBomb(BombSpritePair bsp) {
for(int i = 0; i <= bsp.getBomb().getStrength(); i++) {
if(bd.detect(bsp.getBomb().getX(), bsp.getBomb().getY() + i)) {
Sprite sprite = new Sprite(new Texture("gras.png"));
sprite.setPosition(bsp.getBomb().getX()*16, (bsp.getBomb().getY()+i)*16);
sprites.add(sprite);
System.out.println("RIP"+i);
System.out.println(bsp.getBomb().getStrength());
break;
}
}
}
You may be seeing duplicate print statements if you are calling the detectBomb method multiple times. Putting a breakpoint or print statement at the beginning of this method will help determine what the problem is.
Another thing to keep in mind is that you are creating a new Texture for the Sprite every time the method get executed - it would be wise to only instantiate the Texture once and share it with all subsequent Sprite instances that require it.
I am trying to make a NXT Robot that has attached the Ultrasonic Sensor. It has to drive until the distance is 15, and then the engines have to stop. After it stops it has to turn, but it doesn't work.
import lejos.nxt.*;
public class test {
public static void main(String [] args) throws InterruptedException {
UltrasonicSensor ultra = new UltrasonicSensor(SensorPort.S1);
for (int i = 0; i < 5; i++) {
try {
Motor.B.rotate(-1500 , true);
Motor.C.rotate(-1500 , true);
} catch (Exception E){}
while ( ultra.getDistance() < 15 ) {
Motor.B.backward();
Motor.C.backward();
}
LCD.clear();
LCD.drawString("Distance : "+ultra.getDistance(), 0, 0);
}
Button.waitForAnyPress();
}
}
My old code, which also didn't work:
import lejos.nxt.*;
public class test {
public static void main(String [] args) throws InterruptedException {
UltrasonicSensor ultra = new UltrasonicSensor(SensorPort.S1);
try {
Motor.B.rotate(-720);
Motor.C.rotate(-720);
} catch (Exception E){}
for (int i = 0; i < 5; i++)
{
LCD.drawString("Distance : "+ultra.getDistance(), 0, i);
Thread.sleep(2000);
int maxDistance = ultra.getDistance();
if (maxDistance < 15){
Motor.B.stop();
Motor.C.stop();
}
}
Button.waitForAnyPress();
}
}
Assumptions
Okay, from the looks of things, your code is probably not doing what you want. (In the future, when writing a question on Stack Overflow, please clarify in detail what the expected behavior is, as well as what erroneous behavior you're seeing. Those are usually the first two questions we would ask of you, anyway.)
First of all, you're going to want to ensure that your NXT kit has been set up properly, with your two motors on B and C, and your sensor on S1. If this is so, continue reading.
Code Interpretation
The motor commands:
try {
Motor.B.rotate(-1500, true);
Motor.C.rotate(-1500, true);
} catch (Exception E) {}
look like they're valid motor commands... but wait! You're using a two-wheeled robot, with the motors connected to two wheels that point in opposite directions? But you're using the same distance and direction for your motor's limit angle! If your wheels oppose each other, then this will do nothing but make the robot spin in a circle.
NOTE: Since your motors are configured properly, as written in your comments, ignore this part.
If you change the direction of one of the motors by changing the positive to a negative, then you'll have them both working in unison to move your robot forward (or backwards, if you change the wrong one!)
Also, keep in mind that passing true as the second argument in
Motor.B.rotate(-1500, true);
Motor.C.rotate(-1500, true);
makes this function in a very specific fashion, according to the Javadoc (emphasis mine):
If immediateReturn is true, method returns immediately and the motor stops by itself.
If any motor method is called before the limit is reached, the rotation is canceled.
The first sentence means that this does what we want it to: It tells our motor to find the right limit angle by itself, but don't make our program wait for it. However, the second sentence means that if any other motor commands are called, it will stop moving to the given limit angle. Yeah, that's right. Those next few lines make us stop moving the motors and do what they say instead.
Now, this code is problematic for two reasons:
while (ultra.getDistance() < 30) {
Motor.B.backward();
Motor.C.backward();
}
First, these commands will IMMEDIATELY stop our previous two motor commands from executing, which basically means the motors will jump straight to going "backwards" and looping until the distance sensor reads greater than or equal to 30. This is actually what we want, but we need a bit more...
Second, after your sensor reads the distance greater than 30, your motors are never told to stop! So even when your program is showing you the distance, and waiting for your button to be pressed, it'll still be moving!
A Solution
Okay, there's a few things that need to change:
Your initial motor command is being blocked out by the later commands that tell it to move to the correct position.
Your motors don't stop when they're supposed to.
Below is your code, edited to address each of these issues. I've included notes where I've made changes to show you what I've changed.
import lejos.nxt.*;
public class test {
public static void main(String [] args) throws InterruptedException {
UltrasonicSensor ultra = new UltrasonicSensor(SensorPort.S1);
for (int i = 0; i < 5; i++) {
// No initial motor movement (because it did nothing anyway)
// We change this to approach from either direction.
while (ultra.getDistance() != 30) {
// Check whether it's behind or ahead of it.
// Assuming that B- and C- increase distance, and B+ and C+ decrease it (depends on robot configuration).
// This is called a feedback loop, by the way.
if (ultra.getDistance() < 30) { // Move forward (distance+)
Motor.B.backward();
Motor.C.backward();
} else { // Move backward (distance-)
Motor.B.forward();
Motor.C.forward();
}
}
// We only get here when the distance is right, so stop the motors.
Motor.B.stop();
Motor.C.stop();
LCD.clear();
LCD.drawString("Distance : "+ultra.getDistance(), 0, 0);
}
Button.waitForAnyPress();
}
}
Now, this code isn't perfect; it may have a tendency to oscillate between forward and backward on slippery surfaces (which may turn it slightly to the left or right due to differences in applied torque), or if the sensor misses the correct position and the robot overshoots it.
This code also doesn't wait until the robot stabilizes at the given position, just until the sensor first reports the correct one. Again, this may result in sliding around a bit if the wheels don't have decent traction, the motors are set to smooth acceleration, or if the motors run at too high of a speed.
To correct these flaws, you'd need a more advanced type of feedback loop which accounts for acceleration and slip, and you'd need to wait until the robot stabilizes at the correct position for a short period of time before stopping the motors.
However, this should get you moving in the right direction, so to speak.
EDIT Corrected drive motor directionality, as specified in the comments.
I am programming a game, but I have ran into an error.
When the player collided with an object, player.hasCollided is set to true.
if(playerBounds.intersects(wolfBounds)){
player.hasCollided = true;
player.dead();
}
Now, when hasCollided is true, something from the LoseScreen class is printed out onto the screen:
if(player.hasCollided){
lose.start(g);
}
In player.dead(), the player's speed is set to 0.
public void dead(){
playerSpeed = 0;
coinBank += coinsCollected;
}
The problem is that in my InputHandler class I make it so that on the lose screen, when the choice is 1, and enter is pressed, restartGame() is called.
public void restartGame(){
obstacleWolf.getNewPosition();
obstacleHole.getNewPosition();
hasLost = false;
player.hasCollided = false;
player.playerSpeed = 5;
player.nextX = 1000;
player.coinsCollected = 0;
player.xElapsed = 0;
}
if(lose.choice == 1 && enter){
game.hasLost = false;
game.restartGame();
System.out.println(player.hasCollided + " " + player.playerSpeed);
}
Those variables ARE being set to what they are meant to be set to (for example playerSpeed becomes 5 from 0, and hasCollided is becoming false from true) but the effects are not taking place. So, like I showed before, lose.start(g); is only meant to be called when hasCollided is true, but even when it becomes false, it is still printed out on the screen.
Here is how the relevant variables/methods are being used:
public void move() {
x = x - player.playerSpeed;
}
(All moving objects share the same move method)
Parts of the game class:
public void tick(){
input.tick();
if(gameState){
player.tick();
player.move();
collision();
treeline.move();
obstacleHole.move();
obstacleWolf.move();
coin.move();
coin.tick();
}
I am not sure if I can make this question clearer. I can provide more code from different classes if needed.
The question can't be answered in its current form (see 2 comments above).
The reason for that is current code structure.
You need to refactor code, then you will find the problem.
Put all modification of player fields in methods of Player class.
Access fields only through methods. Making fields private is old good practice.
Then the only code you need to share would be this Player class.
In one thread environment, that's all.
Im creating an 'Avoid the Blocks' game, and for this i need to move a character around a grid (2D array) using the keys GHKJ. Every x amount of turns (decreasing as the level increases) a shadow must appear, then that shadow becomes a block and if the player moves into that bloack they lose a life.
Most of this is done for me other than the seemingly simple taski of getting the blocks to appear, here is my code so far for the falling blocks:
public void rocked(){
int rockInit = turn;
if(rockInit > 1){
int save = turn;
System.out.println(turn + " ");
B.board[ran.nextInt(12)][ran.nextInt(12)] = shadow;
if(save == turn - 3){
B.board[rockLocX][rockLocY] = rock;
}
}
}
The system.println is simply for debugging purposes, checking the values are being accesed. Turn is increased by 1 for every move the player makes, ran.nextInt(12) is a randomly generated number between 0 and 11, and B.board is the playing board.
It looks like you're never changing "save" after you initialize it to "turn". So then when you check if(save == turn-3), it will always be false, and so never move the block in. If you want to keep track of how many turns have passed, I would recommend a private instance variable "int turnsPassed" that you can increment each turn. Then for each level, you can check if (turnsPassed % x == 0), where x is as you've described it. Hope that helps!