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How do I get object collision to work when using the Mouse follow Script?

Posted on 2009-05-13
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Medium Priority
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Last Modified: 2012-05-06
Hi guys, I'm back and still working on my breakout type game.  I have found this awesome script that let's me have my paddle move with my mouse cursor but since I added it, the object collision stopped working.  What I have figured out so far is even though the paddle image is on the screen, the paddle object is still sitting in it's original position and does not collide with the ball.  I seek you excellent advice again.  

Also on a side note, with the follow mouse script, I'm trying to follow on X axis only but when i comment out the Y axis i get multiple javascript page errors, it runs, is there a way to modify it so it only utilizes the X axis?

I have posted the code, everything I think is relevant to this issue, if you need more, just tell me and i'll post the whole thing.

Once again, thanks in advance for the help
// Sections from the rebound.js file
 
 
function init() {
    //instantiate HTML object instance vars
    ball = document.getElementById('idball');
    paddle = document.getElementById('idpaddle');
    score = document.getElementById('score');
    hiScore = document.getElementById('hiScore');
    gameTime = document.getElementById('gameTime');
    //resister key listener with document object
    document.onkeydown = keyListener;
 
//function keyListener(e) {
//    if (!e) {
//        //for IE
//        e = window.event;
//    }
//    if (e.keyCode == 37 && paddleLeft > 10) {
//        //keycode 37 is left arrow
//        paddleLeft -= 10;
//        paddle.style.left = paddleLeft + 'px';
//    }
//    if (e.keyCode == 39 && paddleLeft < 425) {
//        //keycode 39 is right arrow
//        paddleLeft += 10;
//        paddle.style.left = paddleLeft + "px";
//    }
//}
 
function detectCollisions() {
    //just reflect the ball on a collision
    //a more robust engine could change trajectory of
    //the ball based on where the ball hits the paddle
    if (collisionX())
        dx = dx * -1;
    if (collisionY())
        dy = dy * -1;
}
 
function collisionX() {
    //check left and right boundaries
    if (ballLeft < 4 || ballLeft > 480)
        return true;
    return false;
}
 
function collisionY() {
    //check if at top of playing area
    if(ballTop < 4)
    return true;
    //check to see if ball collided with paddle
    if(ballTop >450) {
        if(ballLeft > paddleLeft - 10 && ballLeft < paddleLeft + 64)
            return true;
        }
    return false;
}
 
var divName = 'mypaddle';  // div that is to follow the mouse
                           // (must be position:absolute)
var offX = -45;            // X offset from mouse position
var offY = 0;              // Y offset from mouse position
 
function mouseX(evt) {
	if (!evt) evt = window.event; 
	if (evt.pageX) return evt.pageX; 
	else if (evt.clientX)return evt.clientX + (document.documentElement.scrollLeft ?  document.documentElement.scrollLeft : document.body.scrollLeft); else return 0;}
 
//function mouseY(evt) {
	//if (!evt) evt = window.event;
	//if (evt.pageY) return evt.pageY; 
	//else if (evt.clientY)return evt.clientY + (document.documentElement.scrollTop ? document.documentElement.scrollTop : document.body.scrollTop); 
	//else return 0;}
 
function follow(evt) {if (document.getElementById) {var obj = document.getElementById(divName).style; obj.visibility = 'visible';
obj.left = (parseInt(mouseX(evt))+offX) + 'px';
obj.top = (parseInt(mouseY(evt))+offY) + 'px';}}
document.onmousemove = follow;
 
 
**************************************************
 
//HTML Div Tag
<div id="mypaddle">
            <img src="img\paddle1.gif" id="paddle" alt="" />
        </div>
 
 
*****************************************
 
//CSS Class 
#mypaddle 
{
	position:absolute; 
	overflow:hidden; 
	visibility: hidden; 
	top: 470px;
	width:64px; 
	height:16px;

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Question by:dtolle
  • 2
3 Comments
 
LVL 9

Accepted Solution

by:
Graceful_Penguin earned 1000 total points
ID: 24382446
The errors is caused by this line :
obj.top = (parseInt(mouseY(evt))+offY) + 'px';}}
Whitch calls to the function you commented out. so I also commented it out.

About the object collision, I can't see how the follow script can influence it but I think you need to post code that calls the detectCollisions() function. I think the problem could be there.
// Sections from the rebound.js file
 
 
function init() {
    //instantiate HTML object instance vars
    ball = document.getElementById('idball');
    paddle = document.getElementById('idpaddle');
    score = document.getElementById('score');
    hiScore = document.getElementById('hiScore');
    gameTime = document.getElementById('gameTime');
    //resister key listener with document object
    document.onkeydown = keyListener;
 
//function keyListener(e) {
//    if (!e) {
//        //for IE
//        e = window.event;
//    }
//    if (e.keyCode == 37 && paddleLeft > 10) {
//        //keycode 37 is left arrow
//        paddleLeft -= 10;
//        paddle.style.left = paddleLeft + 'px';
//    }
//    if (e.keyCode == 39 && paddleLeft < 425) {
//        //keycode 39 is right arrow
//        paddleLeft += 10;
//        paddle.style.left = paddleLeft + "px";
//    }
//}
 
function detectCollisions() {
    //just reflect the ball on a collision
    //a more robust engine could change trajectory of
    //the ball based on where the ball hits the paddle
    if (collisionX())
        dx = dx * -1;
    if (collisionY())
        dy = dy * -1;
}
 
function collisionX() {
    //check left and right boundaries
    if (ballLeft < 4 || ballLeft > 480)
        return true;
    return false;
}
 
function collisionY() {
    //check if at top of playing area
    if(ballTop < 4)
    return true;
    //check to see if ball collided with paddle
    if(ballTop >450) {
        if(ballLeft > paddleLeft - 10 && ballLeft < paddleLeft + 64)
            return true;
        }
    return false;
}
 
var divName = 'mypaddle';  // div that is to follow the mouse
                           // (must be position:absolute)
var offX = -45;            // X offset from mouse position
var offY = 0;              // Y offset from mouse position
 
function mouseX(evt) {
	if (!evt) evt = window.event; 
	if (evt.pageX) return evt.pageX; 
	else if (evt.clientX)return evt.clientX + (document.documentElement.scrollLeft ?  document.documentElement.scrollLeft : document.body.scrollLeft); else return 0;}
 
//function mouseY(evt) {
	//if (!evt) evt = window.event;
	//if (evt.pageY) return evt.pageY; 
	//else if (evt.clientY)return evt.clientY + (document.documentElement.scrollTop ? document.documentElement.scrollTop : document.body.scrollTop); 
	//else return 0;}
 
function follow(evt) {if (document.getElementById) {var obj = document.getElementById(divName).style; obj.visibility = 'visible';
obj.left = (parseInt(mouseX(evt))+offX) + 'px';
//obj.top = (parseInt(mouseY(evt))+offY) + 'px';}}
document.onmousemove = follow;
 
 
**************************************************
 
//HTML Div Tag
<div id="mypaddle">
            <img src="img\paddle1.gif" id="paddle" alt="" />
        </div>
 
 
*****************************************
 
//CSS Class 
#mypaddle 
{
	position:absolute; 
	overflow:hidden; 
	visibility: hidden; 
	top: 470px;
	width:64px; 
	height:16px;

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Author Comment

by:dtolle
ID: 24387106
I will give that a try today.
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Author Comment

by:dtolle
ID: 24598104
Sorry it took so long to respond, It worked so far with what i need, thank you!
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