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Set Velocity.X based on which part of sprite is clicked


heisenthurg
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I am making a soccer keep up game, which consists solely of a ball that you click and have to prevent hitting the floor. So far I have got everything working, apart from the left/right movement of the ball. Currently, I have set it so when the ball is clicked, it is given a Y velocity making it go up in the air again. The issue is it goes straight up. I tried generating a random X velocity to make it also go left/right on click, but the problem is it is random. So if the ball is falling from left to right, clicking on the right side of the ball should make it go back left (as a ball would react in real life) but as it is currently random sometimes it will right instead. 

I feel like I need to get the position of the actual click on the sprite, and from that determine which direction the ball should go. Unless there is a better way? I have included my code below:

var game = new Phaser.Game(800, 600, Phaser.AUTO, 'game-wrapper', { preload: preload, create: create, render:render });	

var score = 0;
var text;

function preload() {
	
	//Load Assets
	game.load.image('ball', 'ball.png');	

}	

function create() {

	//Add Game Text
	text = game.add.text(100, 50, "Score: 0", { font: "32px Arial", fill: "#ff0000" });
    text.anchor.set(0.5);

	 //  Enable p2 physics engine
    game.physics.startSystem(Phaser.Physics.P2JS);

    //Enable Impact Events for Collisions/Clicks etc
    game.physics.p2.setImpactEvents(true);

    //Set Background Color
    game.stage.backgroundColor = '#009900';

    //Set Physics - Gravity and Ball 'Weight'
    game.physics.p2.gravity.y = 500;
    game.physics.p2.restitution = 0.9;

    //Add Ball, clip to circle, enable physics on ball
	ball = game.add.sprite(350, 150, 'ball');
	game.physics.p2.enable(ball);
	ball.body.setCircle(80);

	//Stop ball from colliding with world boundaries
	ball.body.collideWorldBounds = false;

	//Allow input on ball, and check for click input
	ball.inputEnabled = true;
	ball.events.onInputDown.add(clickDown, this);

	//Check location of ball to see if it is within boundaries, run function 'offScreen' if not
	ball.checkWorldBounds = true;
	ball.events.onOutOfBounds.add(offScreen, this);

}	


function render() {

   game.debug.spriteInputInfo(ball, 50, 500);


}

function clickDown(ball, pointer) {

	var randX = Math.floor(Math.random()*300) + 1;
	randX *= Math.floor(Math.random()*2) == 1 ? 1 : -1;

	ball.body.velocity.y = -500;
	ball.body.velocity.x = randX;

	
	score += 1;
	text.text = "Score: " + score;

}

function offScreen() {
	alert("You lose!");

}

 

Any help would be appreciated!

Thanks :)

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The simplest way of just having left/right detection I can think of is to have two buttons, each one is half as wide as the ball sprite, and attach them to the ball. Each button when pressed, gives a left/right velocity.

text4163-5.png

Perhaps a more elegant solution would be when the ball is pressed, calculate if the input down X is more or less than the X of the center of the ball sprite. If input down X is greater than the center X of the ball sprite, the right half of the sprite was pressed. Else, must have been left side.

 

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The Phaser example Breakout game has a working example of the latter solution Arcanorum suggested, applying the difference between the clicked point and the center of the sprite to the velocity. 

http://phaser.io/examples/v2/games/breakout

function ballHitPaddle (_ball, _paddle) {

    var diff = 0;

    if (_ball.x < _paddle.x)
    {
        //  Ball is on the left-hand side of the paddle
        diff = _paddle.x - _ball.x;
        _ball.body.velocity.x = (-10 * diff);
    }
    else if (_ball.x > _paddle.x)
    {
        //  Ball is on the right-hand side of the paddle
        diff = _ball.x -_paddle.x;
        _ball.body.velocity.x = (10 * diff);
    }
    else
    {
        //  Ball is perfectly in the middle
        //  Add a little random X to stop it bouncing straight up!
        _ball.body.velocity.x = 2 + Math.random() * 8;
    }

}

 

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