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3rd person camera movement in LWJGL3

I've been following along with ThinMatrix's OpenGL tutorial on making a game in Java recently. However as he uses LWJGL2, and I'm using LWJGL3, there's a few differences that require some work arounds. I'm stuck at one point in particular pertaining to creating a 3rd person character on a "player".
I've done enough so that when I click and drag the screen, the camera rotates around the player like it should. However when I let go and move my mouse to make another rotation, instead of continuing from where the position is, it resets it relative to where my second click is.
As LWJGL3 doesn't have a mouse.getDY() or mouse.getDX(), I made one in my DisplayManager class like so:
public float getDY() {
newMouseY = (float) getMouseY();
float dy = newMouseY - oldMouseY;
oldMouseY = newMouseY;
return dy;
}
public float getDX() {
newMouseX = (float) getMouseX();
float dx = newMouseX - oldMouseX;
oldMouseX = newMouseX;
return dx;
}
And I call it in my camera class like so:
private void calculatePitch(DisplayManager window) {
if (window.isMouseDown(GLFW.GLFW_MOUSE_BUTTON_LEFT)) {
float pitchChange = window.getDY() * 0.2f;
pitch -= pitchChange;
}
}
private void calculateAngleAroundPlayer(DisplayManager window) {
if (window.isMouseDown(GLFW.GLFW_MOUSE_BUTTON_LEFT)) {
float angleChange = window.getDX() * 0.3f;
angleAroundPlayer -= angleChange;
}
}
I'm just not sure if this should work and I'm missing something really obvious, or it can't be done this way. I'm pretty new to game dev.

Managed to figure out the issue, all I had to do was call my getDX() and getDY() functions again after the mouse has been pressed in my calculations:
private void calculatePitch(DisplayManager window) {
if (window.isMouseDown(GLFW.GLFW_MOUSE_BUTTON_LEFT)) {
float pitchChange = window.getDY(window) * 0.2f;
pitch += pitchChange;
}
window.getDY(window);
}
private void calculateAngleAroundPlayer(DisplayManager window) {
if (window.isMouseDown(GLFW.GLFW_MOUSE_BUTTON_LEFT)) {
float angleChange = window.getDX(window) * 0.3f;
angleAroundPlayer -= angleChange;
}
window.getDX(window);
}

How to move a Sprite after rotation In the indicated direction? Libgdx - Java - Android

I have a video game in which an arrow moves towards the side where it is pointing, after rotation the arrow, example:
I need to move the sprite To the same direction in which the arrow points after it has been rotation.
A bit of code As I'm trying to do:
int count = 0;
#Override
protected void handleInput() {
if(Gdx.input.justTouched()){
// move to the direction of pointing:
arrow.setPosition(x, y);
}
}
public void update(float dt){
count++;
// rotate sprite:
arrow.setRotation(count);
}

In the book "Beginning Java Game Development with LibGDX" the author makes a game that I think demonstrates the behaviour you want. The game is "Starfish Collector" from chapter 3. The player moves a turtle to collect starfish. The left and right arrow keys rotate the turtle, and the up arrow key moves the turtle forward in the direction he is currently facing.
The source code for the game can be downloaded from the author's Github account here. (I don't know why he put it in a zip file.)
The relevant code looks like this:
#Override
public void update(float dt) {
// process input
turtle.setAccelerationXY(0, 0);
if (Gdx.input.isKeyPressed(Keys.LEFT)) {
turtle.rotateBy(90 * dt);
}
if (Gdx.input.isKeyPressed(Keys.RIGHT)) {
turtle.rotateBy(-90 * dt);
}
if (Gdx.input.isKeyPressed(Keys.UP)) {
turtle.accelerateForward(100);
}
// ...
Where turtle extends some custom classes that extend Actor.
The code for accelerateForward looks like this:
public void accelerateForward(float speed) {
setAccelerationAS(getRotation(), speed);
}
And then the code for setAccelerationAS looks like this:
// set acceleration from angle and speed
public void setAccelerationAS(float angleDeg, float speed) {
acceleration.x = speed * MathUtils.cosDeg(angleDeg);
acceleration.y = speed * MathUtils.sinDeg(angleDeg);
}
Note that this last bit of code is probably exactly what user unexistential was referring to.
(I recommend this book if you're learning LibGDX and game development. It's very good.)
See also:
Beginning Java Game Development with LibGDX by Lee Stemkoski
Book's source code

The simplest way would be to use the sine and cosine of the rotation amount to determine the x and y components of the translation vector.

I resolved with this page: enter link description here
float mX = 0;
float mY = 0;
int velocity = 5;
private float posAuxX = 0;
private float posAuxY = 0;
int count = 0;
public void update(float dt){
count2++;
flecha.setRotation(count2);
if (count2 >= 360){
count2 = 0;
}
position = new Vector2((float) Math.sin(count2) * velocity,
(float) Math.cos(count2 * velocity));
mX = (float) Math.cos(Math.toRadians(flecha.getRotation()));
mY = (float) Math.sin(Math.toRadians(flecha.getRotation()));
position.x = mX;
position.y = mY;
if (position.len() > 0){
position = position.nor();
}
position.x = position.x * velocity;
position.y = position.y * velocity;
posAuxX = flecha.getX();
posAuxY = flecha.getY();
}
flecha.setPosition(posAuxX, posAuxY);

The paddle of pong keeps shaking without staying at one position

Please look at the following structure of my pong game.
gameLoop(); method
//Only run this in another Thread!
private void gameLoop()
{
//This value would probably be stored elsewhere.
final double GAME_HERTZ = 30.0;
//Calculate how many ns each frame should take for our target game hertz.
final double TIME_BETWEEN_UPDATES = 1000000000 / GAME_HERTZ;
//At the very most we will update the game this many times before a new render.
//If you're worried about visual hitches more than perfect timing, set this to 1.
final int MAX_UPDATES_BEFORE_RENDER = 5;
//We will need the last update time.
double lastUpdateTime = System.nanoTime();
//Store the last time we rendered.
double lastRenderTime = System.nanoTime();
//If we are able to get as high as this FPS, don't render again.
final double TARGET_FPS = 60;
final double TARGET_TIME_BETWEEN_RENDERS = 1000000000 / TARGET_FPS;
//Simple way of finding FPS.
int lastSecondTime = (int) (lastUpdateTime / 1000000000);
while (running)
{
double now = System.nanoTime();
int updateCount = 0;
if (!paused)
{
//Do as many game updates as we need to, potentially playing catchup.
while( now - lastUpdateTime > TIME_BETWEEN_UPDATES && updateCount < MAX_UPDATES_BEFORE_RENDER )
{
updateGame();
lastUpdateTime += TIME_BETWEEN_UPDATES;
updateCount++;
}
//If for some reason an update takes forever, we don't want to do an insane number of catchups.
//If you were doing some sort of game that needed to keep EXACT time, you would get rid of this.
if ( now - lastUpdateTime > TIME_BETWEEN_UPDATES)
{
lastUpdateTime = now - TIME_BETWEEN_UPDATES;
}
//Render. To do so, we need to calculate interpolation for a smooth render.
float interpolation = Math.min(1.0f, (float) ((now - lastUpdateTime) / TIME_BETWEEN_UPDATES) );
//float interpolation = 1.0f;
drawGame(interpolation);
lastRenderTime = now;
//Yield until it has been at least the target time between renders. This saves the CPU from hogging.
while ( now - lastRenderTime < TARGET_TIME_BETWEEN_RENDERS && now - lastUpdateTime < TIME_BETWEEN_UPDATES)
{
Thread.yield();
//This stops the app from consuming all your CPU. It makes this slightly less accurate, but is worth it.
//You can remove this line and it will still work (better), your CPU just climbs on certain OSes.
//FYI on some OS's this can cause pretty bad stuttering. Scroll down and have a look at different peoples' solutions to this.
try {Thread.sleep(1);} catch(Exception e) {}
now = System.nanoTime();
}
}
}
}
updateGame(); method
if(p1_up){
if(player.equals("p1")){
p1.moveUp();
}
else
{
p2.moveUp();
}
}
else if(p1_down){
if(player.equals("p1")){
p1.moveDown();
}
else
{
p2.moveDown();
}
}
moveUp(); moveDown(); method of paddle
public void moveUp(){
last_y = y;
last_x = x;
y -= 50.0;
}
public void moveDown(){
last_y = y;
last_x = x;
y += 50.0;
}
drawGame(interpolation); method
public void paintComponent(Graphics g)
{
super.paintComponent(g);
for(int i=0;i<balls.size();i++){
paintBall(g, balls.get(i));
}
drawPaddle(g, p1);
drawPaddle(g, p2);
}
public void drawPaddle(Graphics g, Paddle p){
paddle_drawX = (int)((p.x - p.last_x)*interpolation + p.last_x);
paddle_drawY = (int)((p.y - p.last_y)*interpolation + p.last_y);
g.drawRect(paddle_drawX, paddle_drawY, 10, 50);
}
I am a beginner in game programming so i don't have a good idea about game loops. I found the above fixed time-step game loop in the internet and used it as the game loop for my game. The loop makes the ball move smoothly but the paddle isn't staying at one place when moved. When I move my paddle by pressing one down key stroke then the paddle keeps shaking
without stopping in one spot. The y coordinates of the paddle keeps changing like
33, 45, 20, 59, 34, 59, 34, 59, 33, 59, 34, 58
I know the problem is in interpolation value as it keeps changing value that will change the y coordinate of paddle in render. I have been thinking about this for a while and i don't know how to make the game loop work for any movements so i have come here for some help. I appreciate any suggestion/help!
Here is my full Paddle class.
public class Paddle
{
float x;
float y;
float last_y;
float last_x;
public Paddle(int x, int y)
{
this.x = x;
this.y = y;
this.last_x = x;
this.last_y = y;
}
public void setNewX(int d){
last_y = y;
last_x = x;
x = d;
}
public void setNewY(int d){
last_y = y;
last_x = x;
y = d;
}
public void moveUp(){
last_y = y;
last_x = x;
y -= 50.0;
}
public void moveDown(){
last_y = y;
last_x = x;
y += 50.0;
}
}
and i initiate the paddle position in the main class through global variable.
public Paddle p1 = new Paddle(10, 10);
public Paddle p2 = new Paddle(950, 10);
I have following event listeners for handling key strokes.
Action handle_up_action = new AbstractAction(){
public void actionPerformed(ActionEvent e){
p1_up = true;
}
};
Action handle_up_action_released = new AbstractAction(){
public void actionPerformed(ActionEvent e){
p1_up = false;
}
};
Action handle_down_action = new AbstractAction(){
public void actionPerformed(ActionEvent e){
p1_down = true;
}
};
Action handle_down_action_released = new AbstractAction(){
public void actionPerformed(ActionEvent e){
p1_down = false;
}
};

What are you trying to achieve with interpolation? From my understanding, it represents the percentage of time elapsed between previous previous and next "update time".
So it should progress continuously from 0 to 1 each 33.3 ms.
I don't know how you use this interpolation variable in the paintBall method, but for the paddles, it will draw your paddle at a "pseudo random position" between p.x;p.y and p.last_x;p.last_y (depending on the time between the two updateGame()).
In order to correct this, from your loop logic, you should understand that every game entity (balls, paddles, ...) must have two states (the positions):
- the logical state, which is updated only each TIME_BETWEEN_UPDATES
- the visual state, which can be updated anytime, at each render.
It is the same as if you have a set of points (which represent the logical states) and you want to interpolate anywhere between this points (reprensenting the visual state).
Your code is like this.
First solution
The simplest way to correct the paddle shaking, is to avoid the interpolation and use:
public void drawPaddle(Graphics g, Paddle p){
paddle_drawX = (int)p.x;
paddle_drawY = (int)p.y;
g.drawRect(paddle_drawX, paddle_drawY, 10, 50);
}
But your movement will look like this (visual position will be changed only each TIME_BETWEEN_UPDATES)
Second solution
You want p.x;p.y to be the logical position, but the visual position should be interpolated between p.last_x;p.last_y and the logical position if the rendering is done between the input processing and the next updateGame(): you must reset p.last_x;p.last_y when updateGame() is called. To achieve this, call the paddles' updateMovement() method inside updateGame().
public void updateMovement(){
last_y = y;
last_x = x;
}
You can have other solutions, such as to use a speed variable or a movement function, in order to have a smooth movement, accelerations, and so on. It is mainly a generalisation of second solution. It requires bigger changes, but it is more flexible and powerful. To achieve this, you may want to store in paddles the last "update position", and all movement-related variables, such as movement start date. Add a method to retrieve the "visual position" that can be called with any date between two updates, and a method to update the "logical position" called each updateGame().

Java 2d game - Issues with delta time and collision

I'm trying to make a java 2d game, and it seems to work out fine in general. The only problem is, that I can't figure out how to place my "delta" time, to make the movements move the same on 30 FPS as on 1000 FPS.
This is my code for the Entity class:
import java.awt.Rectangle;
import map.Tile;
import graphics.Sprite;
public class Entity {
private String name;
private float positionx, positiony; // Current coordinate
private int targetx,targety; // Target coordinate
private double vx, vy; // Current vector
private double lx, ly; // Last vector
private float speed;
private Sprite sprite;
public Entity(String name, int x, int y, Sprite sprite){
this.name = name;
this.speed = 1f;
this.positionx = x;
this.positiony = y;
this.sprite = sprite;
main.Main.e.addEntity(this); // These kind of calls are ugly, and should be fixed.
}
public void remove(){
main.Main.e.removeEntity(this);
sprite.remove();
}
public void setVector(double vx, double vy){
this.vx = vx;
this.vy = vy;
}
public void update(long delta){
//Multiply modifier to make it act the same on 30 fps as 1000 fps.
vx = vx*delta;
vy = vy*delta;
// Calculate vector
double distance = Math.sqrt((vx * vx) + (vy * vy));
if(distance > 0){ // Have we reached the target yet?
vx = ((vx / distance));
vy = ((vy / distance));
}else{
vx = 0;
vy = 0;
}
//Check collision with objects:
Rectangle rx = new Rectangle((int) (vx+positionx), (int)positiony, 32, 32);
Rectangle ry = new Rectangle((int) positionx, (int)(vy+positiony), 32, 32);
for(Entity e : main.Main.e.getEntities()){
if(this != e){
if(isIntersecting(rx, e.getBounds())){
vx = 0; // Disallow x direction.
}
if(isIntersecting(ry, e.getBounds())){
vy = 0; // Disallow y direction.
}
}
}
//Check tiles:
for(Tile t : main.Main.m.getNeighbours(positionx,positiony)){
if(t.isBlocking()){
if(isIntersecting(rx, t.getBounds())){
vx = 0;
}
if(isIntersecting(ry, t.getBounds())){
vy = 0;
}
}
}
//Update the position:
positionx += vx*speed;
positiony += vy*speed;
//Animate:
animate(vx, vy);
}
public boolean isIntersecting(Rectangle r1, Rectangle r2){
return r1.intersects(r2);
}
public Rectangle getBounds(){
return new Rectangle((int) positionx,(int) positiony,32,32);
}
public void setMoveTo(int x, int y){
this.targetx = x;
this.targety = y;
}
//This function is used by the bots, and not on players (they are setting the vector and use update directly):
public void moveTo(long delta){
setVector((targetx-positionx),(targety-positiony));
update(delta);
}
public void animate(double dx, double dy){
sprite.setPosition((int)positionx, (int)positiony);
if(dx > 0){
sprite.setAnimation(0, 7, 100); // Walk right.
}else if(dx < 0){
sprite.setAnimation(1, 7, 100); // Walk left.
}else{
if(lx > 0){
sprite.setAnimation(2, 3, 200); // Stand right.
}else if(lx < 0){
sprite.setAnimation(3, 3, 200); // Stand left.
}
}
lx = dx;
ly = dy;
}
}
The two problems, that I always run into:
1# The game runs differently on 60FPS than on 500FPS.
2# The game runs the same on 60FPS as 500FPS, but my collision screws up, and I can't move closer than 15px from the other object. I think I need to implement something like: If I can't get 10px closer, then move it 10px closer, but I don't know how to implement it.
How can I implement it correctly? That would help a lot!

The easiest way would be to consider that if you want a constant displacement with a constant velocity you can scale all the deltas relative to the delta of 30 FPS like so:
So if you run at 60 FPS but want the same displacement as on 30FPS alpha would be (1/30)/(1/60) = 2
So
Remove vx = vx*delta;
vy = vy*delta;
and change your position update to
alpha = (1.0/30)*delta;
positionx += alpha*vx*speed;
positiony += alpha*vy*speed;
This is only a crude solution, let me know how it works, I will drop in later and update for a more correct solution (taking into account that delta is not always 1/FPS due to rendering and computation taking some time).
Edit: Variable delta will come later. But some optimizations:
You don't need to construct a rectangle in both Y and X for collisiondetection, try drawing two rectangles, if they intersect they do so on both axis. Just create a rectangle from vx + posx, vy+posy and check for intersection with this.
The above should half your collisionchecks. For further optimization consider using a QuadTree an implementation can be found here.
For the problem of "blocky" collision testing (where you stop X pixels from the blocking object). You can do the following, in pseudocode:
if(new position will make this colide)
while(this.position is more than one pixel away from blocking object)
keep moving one pixel
This will make you stop 1px from the target.

Pendulum simulation only performing one period

I am making a simulation of a pendulum, but it only performs one swing before sending close to random positions for the bob to be at. Essentially, it does not go backwards.
I have tried to change the direction using the goingForward boolean, but it still doesnt work.
public class AnimationPane extends JPanel {
// START CHANGEABLE VARIABLES
private double startAngle = -60.0; // degrees
private double mass = 1; // kilogrammes
private int radius = 10; // m
private double gravity = 9.80665; // m/s^2 // on earth: 9.80665
// END CHANGEABLE VARIABLEs
private BufferedImage ball;
private BufferedImage rope;
private int pointX = 180;
private int pointY = 50;
private double endAngle = Math.abs(startAngle); // absolute value of startAngle
private double angle = startAngle; // current angle
private double circum = (2 * Math.PI * radius); // m
private double distance = 0; // m
private double velocity = 0; // m/s
private double totalEnergy = ((radius) - (Math.cos(Math.toRadians(angle)) * radius)) * gravity * mass + 0.00001;
private double previousE;
private int xPos = 0; // for program
private int yPos = 0; // for program
private boolean goingForward = true;
private double height = 0;
public AnimationPane() {
try {
ball = ImageIO.read(new File("rsz_black-circle-mask-to-fill-compass-outline.png"));
Timer timer = new Timer(100, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
double angleRad = Math.toRadians(Math.abs(angle));
double potentialE = ((radius) - (Math.cos(angleRad) * radius)) * gravity * mass;
Double pE = new Double(potentialE);
height = (radius - (Math.cos(angleRad) * radius));
double kineticE = totalEnergy - pE;
if (kineticE <= 0 || angle >= endAngle) {
if (goingForward == true) {
goingForward = false;
}
else
{
goingForward = true;
}
kineticE = 0.1;
angle = 60;
}
velocity = Math.sqrt(2 * kineticE / mass);
double ratio = distance / circum;
if (goingForward == true) {
distance = distance + (velocity / 10);
angle = startAngle + (360 * ratio);
}
else {
distance = distance - (velocity / 10);
angle = startAngle - (360 * ratio);
}
double angles = Math.toRadians(angle);
double xDouble = Math.sin(angles) * (radius * 10);
Double x = new Double(xDouble);
xPos = x.intValue() + 150;
double yDouble = Math.cos(angles) * (radius * 10);
Double y = new Double(yDouble);
yPos = y.intValue() + 50;
repaint();
}
});
timer.setRepeats(true);
timer.setCoalesce(true);
timer.start();
} catch (IOException ex) {
}
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawLine(xPos + 20, yPos + 20, pointX, pointY);
g.drawImage(ball, xPos, yPos, this);
}
}
I would really appreciate some help getting this to work.
Thank you

I could not debug your code, which was uneasy to work with and sometimes to understand (you use a lot of integer literals in your code, which hides their semantic, I have no idea what was your intention on some statements).
Therefore, I rewrote it using the solution of the differential equation for small oscillations. It works, you can take it as a clean base to implement it again the way you wanted. Note that as Andy Turner pointed it, you should not have to worry about the fact of going forward or backward. You have an equation, you solve it, it gives you the position of the ball at any time. If you want something which is accurate for large angles, I suggest you go on Wikipedia to see the movement equation in this case. Last option, you could numerically solve the differential equation although I would personally don't know how to do it at first glance.
package stackoverflow;
public class AnimationPane extends JPanel {
private static final long serialVersionUID = 1L;
private static final double GRAVITY = 9.80665;
private BufferedImage ball;
private final Point fixedCordPoint;
private final int cordLength;
private final double startAngle;
private double currentAngle;
private final double pulsation;
private final Point ballPos = new Point();
private int time = 1;
public AnimationPane(Point fixedCordPoint, int cordLength, double startAngleRadians) {
this.fixedCordPoint = new Point(fixedCordPoint);
this.cordLength = cordLength;
this.pulsation = Math.sqrt(GRAVITY / cordLength);
this.startAngle = startAngleRadians;
this.currentAngle = startAngleRadians;
this.ball = loadImage(new File("ball.jpg"));
}
private BufferedImage loadImage(File file) {
try {
return ImageIO.read(file);
} catch (IOException e) {
throw new RuntimeException("Could not load file : " + file, e);
}
}
public void start() {
Timer timer = new Timer(100, event -> {
ballPos.x = fixedCordPoint.x + (int) Math.round(Math.sin(currentAngle) * cordLength);
ballPos.y = fixedCordPoint.y + (int) Math.round(Math.cos(currentAngle) * cordLength);
repaint();
currentAngle = startAngle * Math.cos(pulsation * time);
time++;
});
timer.setRepeats(true);
timer.setCoalesce(true);
timer.start();
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawLine(ballPos.x, ballPos.y, fixedCordPoint.x, fixedCordPoint.y);
g.drawImage(ball, ballPos.x - ball.getWidth() / 2, ballPos.y - ball.getHeight() / 2, this);
}
public static void main(String[] args) {
JFrame frame = new JFrame();
AnimationPane pendulumAnimationPane = new AnimationPane(new Point(160, 25), 180, - Math.PI / 10);
frame.setContentPane(pendulumAnimationPane);
frame.setSize(400,400);
frame.setVisible(true);
pendulumAnimationPane.start();
}
}

I really can't follow your code. If I had to say where I thought the problem is, I would say that it is the distance variable, and its consequent use in ratio: this seems to be defined as being zero when the pendulum starts. When you switch the direction of the pendulum, I think that it needs to be rebased to zero... Somehow.
You should also separate out your GUI code from your simulation. You can just make it print out the x and y coordinates while you are debugging. For instance, you can write the values to a CSV file, so you can visualize them in Matlab (or whatever) to ensure that your simulation looks right over time.
I would make two suggestions to help you with the simulation:
Don't model it in terms of energy, which is a scalar quantity, meaning that you have to use additional state like a "direction flag" to model which way it is going;
You are going to need an additional state variable. Storing x and y is redundant, since these can be derived directly from the angle (and R, although that is constant). You are modelling a second-order system, so you need that second state variable which models the movement of the system at an instant, as well as its position. For example, you could model the angle and angular velocity over time.
And, of course, don't mess around with degrees - stick to radians :)
(On the matter of velocity, your variable of that name is actually speed - you don't know which direction it moves in, and that information is highly relevant to the dynamics of the system).
The derivation of the method using angle and angular velocity is quite straightforward, although my maths is rusty enough to caution its use without checking carefully!
The rotational form of Newton's second law of motion is:
Torque = moment of inertia * angular acceleration
The torque on the bob is given by -mgR sin angle (m is mass, g is gravity, R is length of pendulum, angle is the angular displacement of the pendulum from vertical). The minus sign is because the force tends to return the bob to vertical;
The moment of inertia of a point mass is mR^2 - this is a reasonable approximation if the pendulum is very long compared to the radius of the bob.
Therefore the angular acceleration is -g sin theta / R. Hopefully this should look like simple harmonic motion - an acceleration proportional to the distance from an equilibrium (for small theta, sin theta is approximately theta) and directed towards it.
You can now put this together into a numerical scheme to simulate the pendulum. For example, using Euler's method:
New angle = old angle + dt * old angular velocity
New angular velocity = old angular velocity vel - dt * g * sin(angle) / R
where dt is your time step.
You can, of course, use higher-order methods like Runge-Kutta to reduce the numerical errors in the simulation, but it is (slightly) more involved.