Develop Reference

Make my rectangle randomly fall down from my screen?

I am trying to make a game and am almost done with the code. But I can't make my rectangle randomly fall down from my screen.
I am coding a car game that is supposed to dodge the other cars. But is not working. can someone help me?
int carx = 200;
int cary = 0;
float speedx = 0;
float speedy = 0;
float accy = 0.1;
color rod = color(255, 0, 0);
color vit = color(255);
final int START_STATE = 1;
final int PLAY_STATE = 2;
final int GAMEOVER_STATE = 3;
final int RESTART = 4;
int state = START_STATE;
void setup() {
size(400, 700);
}
void draw() {
switch (state) {
case START_STATE:
drawStart();
break;
case PLAY_STATE:
drawPlay();
break;
case GAMEOVER_STATE:
drawGameOver();
case RESTART:
drawrestart();
}
}
void init() {
carx = 200;
cary = 0;
speedx = 0;
speedy = 0;
accy = 0.1;
}
void drawStart() {
background(0);
textAlign(CENTER, CENTER);
textSize(16);
text("Click the mouse button to start the game", width / 2, height / 2);
if (mousePressed) {
state = PLAY_STATE;
}
}
void drawGameOver() {
textAlign(CENTER, CENTER);
textSize(20);
text("you have crashed your car", width / 2, height / 2);
if (mousePressed) {
state = PLAY_STATE;
init();
}
}
void drawrestart() {
textAlign(CENTER, CENTER);
textSize(15);
text("press mouse to restart", 200, 400);
if (keyPressed) {
state = RESTART;
}
}
void drawPlay() {
background(0);
if (get(carx, cary) == vit) {
speedy = -1 * speedy;
}
fill(rod);
rect(carx, cary, 50, 30);
if (get(mouseX, 600) == color(255, 0, 0)) {
state = GAMEOVER_STATE;
}
fill(#FFFFFF);
rect(mouseX, 600, 30, 50);
carx += speedx;
cary += speedy;
speedy += accy;
}

The code you have at the moment only has one rectangle fall down from the top for each 'round' of the game. I'm not sure if you wanted to have multiple blocks falling; I think that would be a good next step.
For now, here's a simple hack which will cause the block to fall from a random position each time, like you requested.
At the very start of your code, outside of the functions, place:
boolean randomise;
Then, within void init() you should add:
randomise = true;
Finally, add this section into drawPlay(), right at the start of the function:
if (randomise){
carx = int(random(width-50));
randomise = false;
}
Note that a new random x co-ordinate will only generate every time you set the boolean 'randomise' to true again. So if you generate a new iteration with more than one block falling inside the drawPlay() function, you should bear this in mind and adjust the code accordingly.
------- [EDIT] -------
Hi, glad that this helped.
I've actually noticed another little issue which I will help you fix.
Currently, you are checking at mouseX to see whether there has been a collision. This works (mostly), but if the right side of the player's white car drives through the left edge of a red falling block, then the game continues as though nothing has happened. What should occur is that the game is over because a collision is detected. You want to find out if any part of the two shapes have overlapped.
To do this, you should alter the code like so. In drawPlay(), replace:
if (get(mouseX, 600) == color(255, 0, 0)) {
state = GAMEOVER_STATE;
}
with:
if (get(mouseX, 600) == color(255, 0, 0) || get(mouseX + 30, 600) == color(255, 0, 0)) {
state = GAMEOVER_STATE;
}
This is an OR statement - checking whether either side of the player's car has collided. This way, every time they bump into each other, the game will end.
Now for your question: how to add multiple cars?
There are a few ways you could go about this, but I'll show you the most straightforward.
In drawPlay(), you want to add this little if statement:
if (cary > height){
init();
}
Basically what we're doing here is checking if the previous red block/car has fallen off the bottom of the sketch. If it has, i.e. if the red block's y co-ordinate is larger than the height of the whole sketch, we call init() again. This will reset everything, including making randomise true. Once randomise is true, the previous code you added will select a random start point for the block, and it will fall all over again.
I hope you've understood everything I explained - whilst my code will fix your problem, the best way to learn is to try to solve things by yourself. Check out Dan Shiffman's videos on YouTube. These are a great starting place to get to grips with Processing - hopefully you'll be more confident writing your own code after following along with his examples :)

Use random to generate a random x coordinate:
carx = (int)random(0, width-50);
Reset the position and the speed of the care, once the car reached to bottom of the window:
void drawPlay() {
if (cary > height) {
carx = (int)random(0, width-50);
cary = 0;
speedy = 0;
}
// [...]

Matrixes and for loops becoming inconsistent?

This is a follow-up post to my previous question, here. I got a remarkable response to instead of using array data tracking, to use matrixes. Now, the code here works just as planned (as in, the rectangles somewhat most of the time get filled in properly with white), but it's very inconsistent. When holding the left or right mouse button the colors phase over each other in a battle of randomness, and I don't know nearly that much about why this is happening. Just for reference, I'm using Java in Processing 3.
This is a result that I made with the project. As you can see, it looks fine.
Except for that jitter when hovering over a rect, and that more than not the rectangles are not being filled in half the time. And plus, the hover color is cycling almost randomly.
int cols, rows;
int scl = 20;
boolean[][] matrix = new boolean[scl+1][scl+1];
void setup() {
size(400, 400);
int w = 400;
int h = 400;
cols = w / scl;
rows = h / scl;
}
void draw() {
background(255);
for (int x = 0; x < cols; x++) {
for (int y = 0; y < rows; y++) {
int xpos = x*scl;
int ypos = y*scl;
stroke(55);
if ((mouseX >= xpos && mouseX <= xpos+scl) &&
(mouseY >= ypos && mouseY <= ypos+scl)) {
fill(75);
if (mousePressed == true) {
println("Clicked at: " + xpos + " and " + ypos);
if (!matrix[xpos/scl][ypos/scl]) {
matrix[xpos/scl][ypos/scl] = true;
} else {
matrix[xpos/scl][ypos/scl] = false;
}
fill(100);
//here is the desired location for the fill to remain constant even
//after unclicking and leaving hover
}
println("Mouse at: " + xpos + " and " + ypos);
} else {
fill(50);
}
if (matrix[x][y]) {
//fill(204, 102, 0);
fill(240);
rect(xpos, ypos, scl, scl);
}
rect(xpos, ypos, scl, scl);
}
}
}

Remeber that Processing fires the draw() function 60 times per second.
So your check for whether the mouse is pressed is happening 60 times per second. That means you're toggling the state of whatever cell the mouse is in 60 times per second.
To fix that problem, you might switch to using the event functions like mousePressed() instead of constantly polling every frame.
From the reference:
int value = 0;
void draw() {
fill(value);
rect(25, 25, 50, 50);
}
void mousePressed() {
if (value == 0) {
value = 255;
} else {
value = 0;
}
}
As for certain cells being skipped over, that's because when you move the mouse, it doesn't actually go through every pixel. It "jumps" from frame to frame. Those jumps are usually small enough that humans don't notice it, but they're large enough that it's skipping over cells.
One solution to this is to use the pmouseX and pmouseY variables to calculate a line from the previous mouse position to the current mouse position, and fill in any cells that would have been hit along the way.

processing: trouble using global array in if condition in for loop

I am trying to write a small program that has a given number of balls (in the example code below it's 3) travel back and forth across the screen at different speeds and phases (start offset).
This much has been achieved in the code. Although I want to be able to select the balls (one at a time) using a mouse click.
I have used the word "HIT!!!" to signify in the console that a ball has been clicked.
My problem is that when I run the code below, I only get a "HIT!" in the console when I click the top ball. That is when the first element y[0] matches with the click_Y variable. When I am sure (but obviously mistaken somehow) that there should be matches when I click in the vicinity of y[1] & y[2].
I'd really be grateful for any help with these. As it's gotten to the point where I am starting to stare blankly at the screen. Thanks.
int noCircles; // the number of items in the array (# of circles)
float[] y; // y-position of each circle (fixed)
float[] speed; // speed of each circle
float[] phase; // phase of each circle
float red = 120;
float green = 120;
float blue = 120;
float click_X;
float click_Y;
void setup() {
size(500, 500);
noCircles = 3;
// allocate space for each array
y = new float[noCircles];
speed = new float[noCircles];
phase = new float[noCircles];
// calculate the vertical gap between each circle based on the total number
// of circles
float gap = height / (noCircles + 1);
//setup an initial value for each item in the array
for (int i=0; i<noCircles; i++) {
y[i] = gap * (i + 1);
// y is constant for each so can be calculated once
speed[i] = random(10);
phase[i] = random(TWO_PI);
}
}
void draw() {
background(155);
for (int i=0; i<noCircles; i++) {
// calculate the x-position of each ball based on the speed, phase and
//current frame
float x = width/2 + sin(radians(frameCount*speed[i] ) + phase[i])* 200;
if (dist(x, y[i], click_X, click_Y) <= 20){
println("HIT!!!!!!!!!!!!!!!!!!");
}
ellipse(x, y[i], 20, 20);
click_X = 0;
click_Y = 0;
}
}
void mousePressed() {
println("You clicked******************************************");
click_X = mouseX;
click_Y = mouseY;
println("click_X =" + click_X);
println("click_Y =" + click_Y);
}

Problems like these are best solved by debugging your program. Start by tracing through the code by hand, then add print statements (more than you've already added), and if that doesn't work then don't be afraid to use the debugger.
You're using the click_X and click_Y variables to check the position of the mouse against the position of each ball. Trace through the for loop in your draw() function. What happens at the end of the first iteration?
You reset the values of click_X and click_Y. That's why you aren't detecting any hits on the other circles.
You could probably refactor your code to only reset those variables if something has been hit, but really, I would stop using them altogether.
I'm guessing that you're using those variables because you only want to check when the mouse is pressed? Just use the mousePressed variable for that. Then you can use the mouseX and mouseY variables directly.
Then your if statement would look like this:
if (mousePressed && dist(x, y[i], mouseX, mouseY) <= 20) {
println("HIT: " + i);
}
Also, using separate arrays like this is called parallel arrays, and is general a bad habit to get into. You should probably use classes instead.

Java Android 2D Game - Issue with virtual borders

I'm a computer scientist student and I'm new to programming. To challenge myself, I decided to try my hand at creating a simple 2D android game.
The issue I'm having is related to the borders. I have a player character who can move left and right along the X-axis, although the character is not supposed to go outside of the screen. This works for the most part, but holding the button that sends your characters towards left/right will make the character go through the border.
What I have in terms of code is essentially an if statement in the update() method that checks if the x value of the player character is < 0 (for the left border) and if that statement is true then it prevents the player from clicking the left button again until the right button has been clicked (player's x value is again greater than 0).
How do I solve this? My first idea was that I could have something that checks the gamestate every 5 ms or something and if the player's x value is equal to or less than 0, then set the movement speed to 0 until the right button has been clicked, but I do not know how to implement this check.
Do you have any idea how this could be implemented or if there is a better solution? Thank you very much!
Here's the relevant code:
//In class GamePanel
public void update() {
if (player.getX() <= 4) {
player.setTooFarLeft(true);
MOVESPEED = 0;
}
}
#Override
public boolean onTouchEvent(MotionEvent event) {
if (event.getAction() == MotionEvent.ACTION_DOWN) {
final float scaleFactorX = getWidth() / (WIDTH * 1.f);
final float scaleFactorY = getHeight() / (HEIGHT * 1.f);
Rect right = new Rect((int) ((WIDTH * scaleFactorX) / 3 + (int) (WIDTH * scaleFactorX) / 3), 0, (int) (WIDTH * scaleFactorX), (int) (HEIGHT * scaleFactorY));
Rect left = new Rect(0, 0, (int) (WIDTH * scaleFactorX / 3), (int) (HEIGHT * scaleFactorY));
int x = (int) event.getX();
int y = (int) event.getY();
//Same for right
if (left.contains(x, y) && player.getTooFarLeft()==false) {
if (!player.getPlaying()) {
player.setPlaying(true);
} else {
player.setMovement(4);
player.setLeft(true);
final Handler handler = new Handler();
handler.postDelayed(new Runnable() {
#Override
public void run() {
player.setMovement(8);
}
}, 1000);
}
return true;
}

do if player's x is less than 0, set his x cordinates to 3.

Cropping image lowers quality and border looks bad

Using some math, i created the following java-function, to input a Bitmap, and have it crop out a centered square in which a circle is cropped out again with a black border around it.
The rest of the square should be transparent.
Additionatly, there is a transparent distance to the sides to not damage the preview when sending the image via Messengers.
The code of my function is as following:
public static Bitmap edit_image(Bitmap src,boolean makeborder) {
int width = src.getWidth();
int height = src.getHeight();
int A, R, G, B;
int pixel;
int middlex = width/2;
int middley = height/2;
int seitenlaenge,startx,starty;
if(width>height)
{
seitenlaenge=height;
starty=0;
startx = middlex - (seitenlaenge/2);
}
else
{
seitenlaenge=width;
startx=0;
starty = middley - (seitenlaenge/2);
}
int kreisradius = seitenlaenge/2;
int mittx = startx + kreisradius;
int mitty = starty + kreisradius;
int border=2;
int seitenabstand=55;
Bitmap bmOut = Bitmap.createBitmap(seitenlaenge+seitenabstand, seitenlaenge+seitenabstand, Bitmap.Config.ARGB_8888);
bmOut.setHasAlpha(true);
for(int x = 0; x < width; ++x) {
for(int y = 0; y < height; ++y) {
int distzumitte = (int) (Math.pow(mittx-x,2) + Math.pow(mitty-y,2)); // (Xm-Xp)^2 + (Ym-Yp)^2 = dist^2
distzumitte = (int) Math.sqrt(distzumitte);
pixel = src.getPixel(x, y);
A = Color.alpha(pixel);
R = (int)Color.red(pixel);
G = (int)Color.green(pixel);
B = (int)Color.blue(pixel);
int color = Color.argb(A, R, G, B);
int afterx=x-startx+(seitenabstand/2);
int aftery=y-starty+(seitenabstand/2);
if(x < startx || y < starty || afterx>=seitenlaenge+seitenabstand || aftery>=seitenlaenge+seitenabstand) //seitenrand
{
continue;
}
else if(distzumitte > kreisradius)
{
color=0x00FFFFFF;
}
else if(distzumitte > kreisradius-border && makeborder) //border
{
color = Color.argb(A, 0, 0, 0);
}
bmOut.setPixel(afterx, aftery, color);
}
}
return bmOut;
}
This function works fine, but there are some problems occuring that i wasn't able to resolve yet.
The quality of the image is decreased significantly
The border is not really round, but appears to be flat at the edges of the image (on some devices?!)
I'd appreciate any help regarding that problems. I got to admit that i'm not the best in math and there should probably be a better formula to ceate the border.

your source code is hard to read, since it is a mix of German and English in the variable names. Additionally you don't say which image library you use, so we don't exactly know where the classes Bitmap and Color come from.
Anyway, it is very obvious, that you are operating only on a Bitmap. Bitmap means the whole image is stored in the RAM pixel by pixel. There is no lossy compression. I don't see anything in your source code, that can affect the quality of the image.
It is very likely, that the answer is in the Code that you don't show us. Additionally, what you describe (botrh of the problems) sounds like a very typical low quality JPEG compression. I am sure, somewhere after you call you function, you convert/save the image to a JPEG. Try to do that at that position to BMP, TIFF or PNG and see that the error disappears magically. Maybe you can also set the quality level of the JPEG somewhere to avoid that.
To make it easier for others (maybe) also to find a good answer, please allow me to translate your code to English:
public static Bitmap edit_image(Bitmap src,boolean makeborder) {
int width = src.getWidth();
int height = src.getHeight();
int A, R, G, B;
int pixel;
int middlex = width/2;
int middley = height/2;
int sideLength,startx,starty;
if(width>height)
{
sideLength=height;
starty=0;
startx = middlex - (sideLength/2);
}
else
{
sideLength=width;
startx=0;
starty = middley - (sideLength/2);
}
int circleRadius = sideLength/2;
int middleX = startx + circleRadius;
int middleY = starty + circleRadius;
int border=2;
int sideDistance=55;
Bitmap bmOut = Bitmap.createBitmap(sideLength+sideDistance, sideLength+sideDistance, Bitmap.Config.ARGB_8888);
bmOut.setHasAlpha(true);
for(int x = 0; x < width; ++x) {
for(int y = 0; y < height; ++y) {
int distanceToMiddle = (int) (Math.pow(middleX-x,2) + Math.pow(middleY-y,2)); // (Xm-Xp)^2 + (Ym-Yp)^2 = dist^2
distanceToMiddle = (int) Math.sqrt(distanceToMiddle);
pixel = src.getPixel(x, y);
A = Color.alpha(pixel);
R = (int)Color.red(pixel);
G = (int)Color.green(pixel);
B = (int)Color.blue(pixel);
int color = Color.argb(A, R, G, B);
int afterx=x-startx+(sideDistance/2);
int aftery=y-starty+(sideDistance/2);
if(x < startx || y < starty || afterx>=sideLength+sideDistance || aftery>=sideLength+sideDistance) //margin
{
continue;
}
else if(distanceToMiddle > circleRadius)
{
color=0x00FFFFFF;
}
else if(distanceToMiddle > circleRadius-border && makeborder) //border
{
color = Color.argb(A, 0, 0, 0);
}
bmOut.setPixel(afterx, aftery, color);
}
}
return bmOut;
}

I think that you need to check PorterDuffXferMode.
You will find some technical informations about compositing images modes HERE.
There is some good example of making bitmap with rounded edges HERE. You just need to tweak a bit source code and you're ready to go...
Hope it will help.

Regarding the quality I can't see anything wrong with your method. Running the code with Java Swing no quality is lost. The only problem is that the image has aliased edges.
The aliasing problem will tend to disappear as the screen resolution increases and would be more noticeable for lower resolutions. This might explain why you see it in some devices only.The same problem applies to your border but in that case it would be more noticable since the color is single black.
Your algorithm defines a square area of the original image. To find the square it starts from the image's center and expand to either the width or the height of the image whichever is smaller. I am referring to this area as the square.
The aliasing is caused by your code that sets the colors (I am using pseudo-code):
if ( outOfSquare() ) {
continue; // case 1: this works but you depend upon the new image' s default pixel value i.e. transparent black
} else if ( insideSquare() && ! insideCircle() ) {
color = 0x00FFFFFF; // case 2: transparent white. <- Redundant
} else if ( insideBorder() ) {
color = Color.argb(A, 0, 0, 0); // case 3: Black color using the transparency of the original image.
} else { // inside the inner circle
// case 4: leave image color
}
Some notes about the code:
Case 1 depends upon the default pixel value of the original image i.e. transparent black. It works but better to set it explicitly
Case 2 is redundant. Handle it in the same way you handle case 1. We are only interested in what happens inside the circle.
Case 3 (when you draw the border) is not clear what it expects. Using the alpha of the original image has the potential of messing up your new image if it happens that the original alpha varies along the circle's edges. So this is clearly wrong and depending on the image, can potentially be another cause of your problems.
Case 4 is ok.
Now at your circle's periphery the following color transitions take place:
If border is not used: full transparency -> full image color (case 2 and 4 in the pseudocode)
If border is used: full transparency -> full black -> full image color (cases 2, 3 and 4)
To achieve a better quality at the edges you need to introduce some intermediate states that would make the transitions smoother (the new transitions are shown in italics):
Border is not used: full transparency -> partial transparency with image color -> full image color
Border is used: full transparency -> partial transparency of Black color -> full Black color -> partial transparency of Black color + Image color (i.e. blending) -> Full image color
I hope that helps