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View Full Version : Elastic Trail Script - many problems! Help!!!



mrk13
12-03-2004, 10:18 PM
Hi!
I love your elastic trail script! It's beautiful. I've found it from many sites, always referring to you as the source. The first one worked fine in IE - but not in mozilla, which, of course, is my browser. So I tried again: three different sites, from yours, too: the blue bullets stayed glued to the top bar in IE, moving only sideways, and in mozilla no signs of life at all. Finally I located another working script: the bullets move nicely again in IE, while mozilla plays dead. This is supposed to work in all browsers? So: please help me! I'm trying to make pages for a dear friend, and she likes the trail... I'll glue the code here, ok, beause I've noticed differences in them, and this one works at least partially.
Million thanks, Mark
Here's the script:

<!-- Add the below to the BODY section of your page, immediately following the <body> tag itself: -->
<div id="dot0" style="position: absolute; visibility: hidden; height: 11; width: 11;"> <img src="images/bullet.gif" height=11 width=11> </div>
<div id="dot1" style="position: absolute; height: 11; width: 11;"> <img src="images/bullet.gif" height=11 width=11> </div>
<div id="dot2" style="position: absolute; height: 11; width: 11;"> <img src="images/bullet.gif" height=11 width=11> </div>
<div id="dot3" style="position: absolute; height: 11; width: 11;"> <img src="images/bullet.gif" height=11 width=11> </div>
<div id="dot4" style="position: absolute; height: 11; width: 11;"> <img src="images/bullet.gif" height=11 width=11> </div>
<div id="dot5" style="position: absolute; height: 11; width: 11;"> <img src="images/bullet.gif" height=11 width=11> </div>
<div id="dot6" style="position: absolute; height: 11; width: 11;"> <img src="images/bullet.gif" height=11 width=11> </div>
<script LANGUAGE="JavaScript">
<!-- hide code

/*
Elastic Trail script (By Philip Winston @ pwinston@yahoo.com, URL:

http://www.geocities.com/pwinston/)
Script featured on Dynamicdrive.com
For this and 100's more DHTML scripts, visit http://dynamicdrive.com
*/

var nDots = 7;

var Xpos = 0;
var Ypos = 0;

// fixed time step, no relation to real time
var DELTAT = .01;
// size of one spring in pixels
var SEGLEN = 10;
// spring constant, stiffness of springs
var SPRINGK = 10;
// all the physics is bogus, just picked stuff to
// make it look okay
var MASS = 1;
// Positive XGRAVITY pulls right, negative pulls left
// Positive YGRAVITY pulls down, negative up
var XGRAVITY = 0;
var YGRAVITY = 50;
// RESISTANCE determines a slowing force proportional to velocity
var RESISTANCE = 10;
// stopping criterea to prevent endless jittering
// doesn't work when sitting on bottom since floor
// doesn't push back so acceleration always as big
// as gravity
var STOPVEL = 0.1;
var STOPACC = 0.1;
var DOTSIZE = 11;
// BOUNCE is percent of velocity retained when
// bouncing off a wall
var BOUNCE = 0.75;

var isNetscape = navigator.appName=="Netscape";

// always on for now, could be played with to
// let dots fall to botton, get thrown, etc.
var followmouse = true;

var dots = new Array();
init();

function init()
{
var i = 0;
for (i = 0; i < nDots; i++) {
dots[i] = new dot(i);
}

if (!isNetscape) {
// I only know how to read the locations of the
// <LI> items in IE
//skip this for now
// setInitPositions(dots)
}

// set their positions
for (i = 0; i < nDots; i++) {
dots[i].obj.left = dots[i].X;
dots[i].obj.top = dots[i].Y;
}


if (isNetscape) {
// start right away since they are positioned
// at 0, 0
startanimate();
} else {
// let dots sit there for a few seconds
// since they're hiding on the real bullets
setTimeout("startanimate()", 1000);
}
}



function dot(i)
{
this.X = Xpos;
this.Y = Ypos;
this.dx = 0;
this.dy = 0;
if (isNetscape) {
this.obj = eval("document.dot" + i);
} else {
this.obj = eval("dot" + i + ".style");
}
}


function startanimate() {
setInterval("animate()", 20);
}


// This is to line up the bullets with actual LI tags on the page
// Had to add -DOTSIZE to X and 2*DOTSIZE to Y for IE 5, not sure why
// Still doesn't work great
function setInitPositions(dots)
{
// initialize dot positions to be on top
// of the bullets in the <ul>
var startloc = document.all.tags("LI");
var i = 0;
for (i = 0; i < startloc.length && i < (nDots - 1); i++) {
dots[i+1].X = startloc[i].offsetLeft
startloc[i].offsetParent.offsetLeft - DOTSIZE;
dots[i+1].Y = startloc[i].offsetTop +
startloc[i].offsetParent.offsetTop + 2*DOTSIZE;
}
// put 0th dot above 1st (it is hidden)
dots[0].X = dots[1].X;
dots[0].Y = dots[1].Y - SEGLEN;
}

// just save mouse position for animate() to use
function MoveHandler(e)
{
Xpos = e.pageX;
Ypos = e.pageY;
return true;
}

// just save mouse position for animate() to use
function MoveHandlerIE() {
Xpos = window.event.x + document.body.scrollLeft;
Ypos = window.event.y + document.body.scrollTop;
}

if (isNetscape) {
document.captureEvents(Event.MOUSEMOVE);
document.onMouseMove = MoveHandler;
} else {
document.onmousemove = MoveHandlerIE;
}


function vec(X, Y)
{
this.X = X;
this.Y = Y;
}

// adds force in X and Y to spring for dot[i] on dot[j]
function springForce(i, j, spring)
{
var dx = (dots[i].X - dots[j].X);
var dy = (dots[i].Y - dots[j].Y);
var len = Math.sqrt(dx*dx + dy*dy);
if (len > SEGLEN) {
var springF = SPRINGK * (len - SEGLEN);
spring.X += (dx / len) * springF;
spring.Y += (dy / len) * springF;
}
}


function animate() {
// dots[0] follows the mouse,
// though no dot is drawn there
var start = 0;
if (followmouse) {
dots[0].X = Xpos;
dots[0].Y = Ypos;
start = 1;
}

for (i = start ; i < nDots; i++ ) {

var spring = new vec(0, 0);
if (i > 0) {
springForce(i-1, i, spring);
}
if (i < (nDots - 1)) {
springForce(i+1, i, spring);
}

// air resisitance/friction
var resist = new vec(-dots[i].dx * RESISTANCE,
-dots[i].dy * RESISTANCE);

// compute new accel, including gravity
var accel = new vec((spring.X + resist.X)/MASS + XGRAVITY,
(spring.Y + resist.Y)/ MASS + YGRAVITY);

// compute new velocity
dots[i].dx += (DELTAT * accel.X);
dots[i].dy += (DELTAT * accel.Y);

// stop dead so it doesn't jitter when nearly still
if (Math.abs(dots[i].dx) < STOPVEL &&
Math.abs(dots[i].dy) < STOPVEL &&
Math.abs(accel.X) < STOPACC &&
Math.abs(accel.Y) < STOPACC) {
dots[i].dx = 0;
dots[i].dy = 0;
}

// move to new position
dots[i].X += dots[i].dx;
dots[i].Y += dots[i].dy;

// get size of window
var height, width;
if (isNetscape) {
height = window.innerHeight + window.pageYOffset;
width = window.innerWidth + window.pageXOffset;
} else {
height = document.body.clientHeight + document.body.scrollTop;
width = document.body.clientWidth + document.body.scrollLeft;
}

// bounce off 3 walls (leave ceiling open)
if (dots[i].Y >= height - DOTSIZE - 1) {
if (dots[i].dy > 0) {
dots[i].dy = BOUNCE * -dots[i].dy;
}
dots[i].Y = height - DOTSIZE - 1;
}
if (dots[i].X >= width - DOTSIZE) {
if (dots[i].dx > 0) {
dots[i].dx = BOUNCE * -dots[i].dx;
}
dots[i].X = width - DOTSIZE - 1;
}
if (dots[i].X < 0) {
if (dots[i].dx < 0) {
dots[i].dx = BOUNCE * -dots[i].dx;
}
dots[i].X = 0;
}

// move img to new position
dots[i].obj.left = dots[i].X;
dots[i].obj.top = dots[i].Y;
}
}

// end code hiding -->
</script>