Basically below is my script for a prototype which uses 128x128 tiles to draw a map on a canvas which user can drag to move around.
Script does work. However I have a few problems to be solved:
1. Poor performance and I can't figure out why.
2. I am missing a method to buffer the tiles before the actual drawing.
3. If you notice any other issues also that could help me to make things run more smoothly it would be fantastic.
Some explanations for the script:
variables
coordinates - Defines the actual images to be displayed. Image file names are type of '0_1.jpg', where 0 is Y and 1 is X.
mouse_position - As name says, is keeping record of mouse position.
position - This is a poorly named variable. It defines the position of the context drawn on canvas. This changes when user drags the view.
Any assistance would be appreciated greatly. Thank you.
var coordinates = [0, 0];
var mouse_position = [0, 0];
var position = [-128, -128];
var canvas = document.getElementById('map_canvas');
var context = canvas.getContext('2d');
var buffer = [];
var buffer_x = Math.floor(window.innerWidth/128)+4;
var buffer_y = Math.floor(window.innerHeight/128)+4;
var animation_frame_request = function() {
var a = window.requestAnimationFrame;
var b = window.webkitRequestAnimationFrame;
var c = window.mozRequestAnimationFrame;
var d = function(callback) {
window.setTimeout(callback, 1000/60);
}
return a || b || c || d;
}
var resizeCanvas = function() {
window.canvas.width = window.innerWidth;
window.canvas.height = window.innerHeight;
window.buffer_x = Math.floor(window.innerWidth/128)+4;
window.buffer_y = Math.floor(window.innerHeight/128)+4;
window.buffer = [];
for (row = 0; row < window.buffer_y; row++) {
x = [];
for (col = 0; col < window.buffer_x; col++) {
x.push(new Image());
}
window.buffer.push(x);
}
}
var render = function() {
animation_frame_request(render);
for (row = 0; row < window.buffer_y; row++) {
for (col = 0; col < window.buffer_x; col++) {
cy = window.coordinates[1]+row;
cx = window.coordinates[0]+col;
window.buffer[row][col].src = 'map/'+cy+'_'+cx+'.jpg';
}
}
for (row = 0; row < window.buffer_y; row++) {
for (col = 0; col < window.buffer_x; col++) {
window.context.drawImage(window.buffer[row][col],
window.position[0]+col*128,
window.position[1]+row*128, 128, 128);
}
}
}
var events = function() {
window.canvas.onmousemove = function(e) {
if (e['buttons'] == 1) {
window.position[0] += (e.clientX-window.mouse_position[0]);
window.position[1] += (e.clientY-window.mouse_position[1]);
if (window.position[0] >= 0) {
window.position[0] = -128;
window.coordinates[0] -= 1;
} else if (window.position[0] < -128) {
window.position[0] = 0;
window.coordinates[0] += 1;
}
if (window.position[1] >= 0) {
window.position[1] = -128;
window.coordinates[1] -= 1;
} else if (window.position[1] < -128) {
window.position[1] = 0;
window.coordinates[1] += 1;
}
render();
}
window.mouse_position[0] = e.clientX;
window.mouse_position[1] = e.clientY;
}
}
window.addEventListener('resize', resizeCanvas, false);
window.addEventListener('load', resizeCanvas, false);
window.addEventListener('mousemove', events, false);
resizeCanvas();
To get better performance you should avoid changing the src of img nodes and move them around instead.
A simple way to minimize the number of img nodes handled and modified (except for screen positioning) is to use an LRU (Least Recently Used) cache.
Basically you keep a cache of last say 100 image nodes (they must be enough to cover at least one screen) by using a dictionary mapping the src url to a node object and also keeping them all in a doubly-linked list.
When a tile is required you first check in the cache, and if it's already there just move it to the front of LRU list and move the img coordinates, otherwise create a new node and set the source or, if you already hit the cache limit, reuse the last node in the doubly-linked list instead. In code:
function setTile(x, y, src) {
var t = cache[src];
if (!t) {
if (cache_count == MAXCACHE) {
t = lru_last;
t.prev.next = null;
lru_last = t.prev;
t.prev = t.next = null;
delete cache[t.src]
t.src = src;
t.img.src = src;
cache[t.src] = t;
} else {
t = { prev: null,
next: null,
img: document.createElement("img") };
t.src = src;
t.img.src = src;
t.img.className = "tile";
scr.appendChild(t.img);
cache[t.src] = t;
cache_count += 1;
}
} else {
if (t.prev) t.prev.next = t.next; else lru_first = t.next;
if (t.next) t.next.prev = t.prev; else lru_last = t.prev;
}
t.prev = null; t.next = lru_first;
if (t.next) t.next.prev = t; else lru_last = t;
lru_first = t;
t.img.style.left = x + "px";
t.img.style.top = y + "px";
scr.appendChild(t.img);
}
I'm also always appending the requested tile to the container so that it goes in front of all other existing tiles; this way I don't need to remove old tiles and they're simply left behind.
To update the screen I just iterate over all the tiles I need and request them:
function setView(x0, y0) {
var w = scr.offsetWidth;
var h = scr.offsetHeight;
var iy0 = y0 >> 7;
var ix0 = x0 >> 7;
for (var y=iy0; y*128 < y0+h; y++) {
for (var x=ix0; x*128 < x0+w; x++) {
setTile(x*128-x0, y*128-y0, "tile_" + y + "_" + x + ".jpg");
}
}
}
most of the time the setTile request will just update the x and y coordinates of an existing img tag, without changing anything else. At the same time no more than MAXCACHE image nodes will be present on the screen.
You can see a full working example in
http://raksy.dyndns.org/tiles/tiles.html
Related
To fully understand this note this; `when the page loads it gets the area of the image (width * height) and creates all the x,y positions for all the positions in the area.
This works fine.
When I have another area from pos x,y and with also an area (width * height) should pop the positions from the first list so it can separate the two areas.
Little bug I noticed is I get little lines that are horizontal to the selected area and they don't extend far from that. I believe the reason is instead of making a clean square inside the image every line is offseted by a pixel or two.
Here's a video of the behaviour https://youtu.be/v1b6dEmfxQw
so since there's already an all positions list this code created a clone of the array and removes the positions.
var drop_boxes = $('.drop-box');
var area_grid = [];
var image_width = $('.img-class')[0].naturalWidth;
var image_height = $('.img-class')[0].naturalHeight;
drop_boxes.each(function() {
var position = $(this).position();
var width = $(this).width();
var height = $(this).height();
var positions_clone = positions.slice(0);
//console.log(positions_clone.length);
var top_offset = parseInt((position['top'] * image_width)/img_width);
var left_offset = parseInt((position['left'] * image_height)/img_height);
position['top'] = top_offset;
position['left'] = left_offset;
var width_offset = parseInt((width * image_width)/img_width);
var height_offset = parseInt((height * image_height)/img_height);
var width_counter = 0;
var height_counter = 0;
var area = width_offset * height_offset;
console.log(position);
console.log(width_offset);
console.log(height_offset);
if (position['top'] < image_height-1 && position['left'] < image_width) {
for (counter = 0; counter < area; counter++) {
var pos = [parseInt(position['left']+width_counter), parseInt(position['top']+height_counter)];
var index = positions.findIndex(function(item) {
// return result of comparing `data` with `item`
// This simple implementation assumes that all `item`s will be Arrays.
return pos.length === item.length && item.every(function(n, i) { return n === pos[i] });
});
//console.log(pos);
if (index > -1) {
positions_clone.splice(index, 1);
}
//area_grid.push(pos);
if (width_counter == width_offset) {
width_counter = 0;
height_counter += 1;
}
if (counter%100 == 0) {
var percentage = Math.round((counter/area)*100, 2);
console.log("Percentage: "+percentage+"%" + " "+counter);
}
width_counter += 1;
}
console.log(positions_clone.length);
console.log(area_grid.length);
areas[area_counter] = {'area': area_grid, 'positions': positions_clone};
parent.find('.area').text(area_counter);
area_counter += 1;
}
any clues in fixing it will be appreciated. I've showed how it behaves after commenting out certain parts of the code in the video.
Change
var index = positions.findIndex(function(item) {
to
var index = positions_clone.findIndex(function(item) {
Because after each splice, the indices of the original positions doesn't change but you are still using those indices to splice the clone.
I have recently been working on a web based project using canvas on HTML5. The program consists of a 16x16 grid of tiles that have been pseudo-randomly generated. I am relatively new to canvas, but have built this program in several other environments, none of which however compile successfully to a web based language. this is the main code section that is giving me bother:
var A = 8765432352450986;
var B = 8765432352450986;
var M = 2576436549074795;
var X = 1;
var rx = 0;
var ry = 0;
this.image = new Image();
var i = 0;
var ii = 0;
while(i < 16)
{
while(ii < 16)
{
this.image = new Image();
this.image.src = "textures/grass.png";
x = (((A*X)+B)%M)%M;
if((x/2)%1 == 0)
{
this.image.src = "textures/grass.png";
}
if((x/8)%1 == 0)
{
this.image.src = "textures/hill.png";
}
if((x/21)%1 == 0)
{
this.image.src = "textures/trees.png";
}
if((x/24)%1 == 0)
{
this.image.src = "textures/sea.png";
}
if((x/55)%1 == 0)
{
this.image.src = "textures/mountain.png";
}
if((x/78)%1 == 0)
{
this.image.src = "textures/lake.png";
}
if((x/521)%1 == 0)
{
this.image.src = "textures/volcano.png";
}
if((x/1700)%1 == 0)
{
this.image.src = "textures/shrine.png";
}
if((x/1890)%1 == 0)
{
this.image.src = "textures/outpost.png";
}
if((x/1999)%1 == 0)
{
this.image.src = "textures/civ.png";
}
ctx = myGameArea.context;
ctx.drawImage(this.image,rx, ry, 20, 20);
ii ++;
rx += 20;
}
i ++;
rx = 0;
ry += 16;
}
I would like canvas to draw along the lines of this code above, effectively generating a grid like this
pre generated grid image
(please try and ignore the obvious bad tile drawings, I planned on either finding an artist or trying slightly harder on them when I get the game fully working.)
The black square is a separate movable object. I haven't got as far as implementing it in this version, but if you have any suggestions for it please tell me
in the full html file I have now, the canvas renders but none of the background (using the w3schools tutorials, I can make objects render however)
In short: how do I render a background consisting of a 16x16 grid of pseudo-random tiles on an event triggered or on page loaded, using canvas or if that does not work another web based technology
Thank you for your time.
A few problems but the main one is that you need to give an image some time to load before you can draw it to the canvas.
var image = new Image();
image.src = "image.png";
// at this line the image may or may not have loaded.
// If not loaded you can not draw it
To ensure an image has loaded you can add a onload event handler to the image
var image = new Image();
image.src = "image.png";
image.onload = function(){ ctx.drawImage(image,0,0); }
The onload function will be called after all the current code has run.
To load many images you want to know when all have loaded. One way to do this is to count the number of images you are loading, and then use the onload to count the number of images that have loaded. When the loaded count is the same as the loading count you know all have loaded and can then call a function to draw what you want with the images.
// Array of image names
const imageNames = "grass,hill,trees,sea,mountain,lake,volcano,shrine,outpost,civ".split(",");
const images = []; // array of images
const namedImages = {}; // object with named images
// counts of loaded and waiting toload images
var loadedCount = 0;
var imageCount = 0;
// tile sizes
const tileWidth = 20;
const tileHeight = 20;
// NOT SURE WHERE YOU GOT THIS FROM so have left it as you had in your code
// Would normally be from a canvas element via canvasElement.getContext("2d")
var ctx = myGameArea.context;
// seeded random function encapsulated in a singleton
// You can set the seed by passing it as an argument rand(seed) or
// just get the next random by not passing the argument. rand()
const rand = (function(){
const A = 8765432352450986;
const B = 8765432352450986; // This value should not be the same as A?? left as is so you get the same values
const M = 2576436549074795;
var seed = 1;
return (x = seed) => seed = ((A * x) + B) % M;
}());
// function loads an image with name
function addImage(name){
const image = new Image;
image.src = "textures/" + name + ".png";
image.onload = () => {
loadedCount += 1;
if(loadedCount === imageCount){
if(typeof allImagesLoaded === "function"){
allImagesLoaded();
}
}
}
imageCount += 1;
images.push(image);
namedImages[name] = image;
}
imageNames.forEach(addImage); // start loading all the images
// This function draws the tiles
function allImagesLoaded(){ /// function that is called when all the images have been loaded
var i, x, y, image;
for(i = 0; i < 256; i += 1){ // loop 16 by 16 times
ctx.drawImage(
images[Math.floor(rand()) % images.length]; //random function does not guarantee an integer so must floor
(i % 16) * tileWidth, // x position
Math.floor(i / 16) * tileHeight, // y position
tileWidth, tileHeight // width and height
);
}
}
I have a scenario in which I am having a canvas, I am dragging some drawing from the left side of the canvas and dropping it on the right side of it and if I am dropping one box near to another one it also clubbing together. Now I need to do two more things -
First, as soon as I am clubbing one with another I want to give this set, of more than one boxes, a treatment of one box. meaning that if I am dragging any one of the box which are clubbed together, whole set of the boxes should be dragged together.
second, as and when I am dropping the boxes I want to generate some plain text based on the box which has been dropped, for example if I dropped "first box", the plain text should be something like "you dropped first box first". And this thing I need to do on the sequence, meaning if the second box is appearing first the text according to that box should appear first.
Here is the code which I have completed
<script type="text/javascript">
window.onload = function(){
draw();
}
</script>
<body style="margin: 0;padding:0;clear:both; cursor: pointer">
<canvas id="canvas" tabindex="1" style="float:left" ></canvas>
<div id="plainEnglish" tabindex="2" style="float: left;"></div>
</body>
<script>
var c = document.getElementById("canvas");
var ctx = c.getContext("2d");
c.width = 600;
c.height = 300;
//My mouse coordinates
var x,y;
c.addEventListener("mousedown",down);
c.addEventListener("mousemove",move);
c.addEventListener("mouseup",up);
var r = 0;
function counter() {
r++;
console.log(r);
}
//I'll save my boxes in this array
var myBoxes = new Array();
// Those boxes which I have moved to droppable area of the canvas.
var myDroppedBoxes = new Array();
//This function describes what a box is.
//Each created box gets its own values
function box(x,y,w,h,rgb,text) {
this.x = x,
this.y = y;
this.xS = x; //saving x
this.yS = y; //saving y
this.w = w;
this.h = h;
this.rgb = rgb;
this.text = text;
//to determine if the box is being draged
this.draging = false;
this.isBeingDragged = false;
}
//Let's make some boxes!!
myBoxes[0] = new box(20,20,75,20,"#6AA121","First");
myBoxes[1] = new box(20,50,75,20,"#6AA121", "Second");
myBoxes[2] = new box(20,80,75,20,"#6AA121","third");
//here we draw everything
function draw() {
ctx.clearRect(0,0,c.width,c.height);
//Dropable area
ctx.fillStyle="red";
ctx.fillRect(c.width/2,0,c.width,c.height);
//Boxes!
for (var i = 0; i<myBoxes.length; i++) {
var b = myBoxes[i];
if (b.draging) { //box on the move
//Also draw it on the original spot
ctx.fillStyle=b.rgb;
ctx.fillRect(b.xS,b.yS,b.w,b.h);
ctx.strokeRect(b.xS,b.yS,b.w,b.h);
ctx.font = "14px Arial";
ctx.strokeText(b.text, b.xS + 5 , b.yS + 15);
}
ctx.fillStyle=b.rgb;
ctx.fillRect(b.x,b.y,b.w,b.h);
ctx.strokeRect(b.x,b.y,b.w,b.h);
ctx.font = "14px Arial";
ctx.strokeText(b.text, b.x + 5 , b.y + 15);
}
for(var i = 0; i< myDroppedBoxes.length; i++) {
var b = myDroppedBoxes[i];
ctx.fillStyle=b.rgb;
ctx.fillRect(b.x,b.y,b.w,b.h);
ctx.strokeRect(b.x,b.y,b.w,b.h);
ctx.font = "14px Arial";
ctx.strokeText(b.text, b.x + 5 , b.y + 15);
}
}
function down(event) {
event = event || window.event;
x = event.pageX - c.offsetLeft,
y = event.pageY - c.offsetTop;
for (var i = 0; i<myBoxes.length; i++) {
var b = myBoxes[i];
if (x>b.xS && x<b.xS+b.w && y>b.yS && y<b.yS+b.h) {
myBoxes[i].draging = true;
myBoxes[i].isBeingDragged = true;
}
}
for (var i = 0; i<myDroppedBoxes.length; i++) {
var b = myDroppedBoxes[i];
if (x>b.x && x<b.x + b.w && y>b.y && y<b.y + b.h) {
b.draging = true;
b.isBeingDragged = true;
}
}
draw();
}
function move(event) {
event = event || window.event;
x = event.pageX - c.offsetLeft,
y = event.pageY - c.offsetTop;
for (var i = 0; i<myBoxes.length; i++) {
var b = myBoxes[i];
if (b.draging && b.isBeingDragged) {
myBoxes[i].x = x;
myBoxes[i].y = y;
if (b.x>c.width/2) {
var length = myDroppedBoxes.length ;
myDroppedBoxes[length] = new box(x,y,b.w,b.h,b.rgb,b.text);
myDroppedBoxes[length].draging = true;
myDroppedBoxes[length].isBeingDragged = true;
b.x = b.xS;
b.y = b.yS;
b.isBeingDragged = false;
}
}
}
for (var i = 0; i<myDroppedBoxes.length; i++) {
var b = myDroppedBoxes[i];
if (b.draging && b.isBeingDragged) {
b.x = x;
b.y = y;
}
}
draw();
}
function up(event) {
event = event || window.event;
x = event.pageX - c.offsetLeft,
y = event.pageY - c.offsetTop;
for (var i = 0; i< myBoxes.length; i++) {
var b = myBoxes[i];
if (b.draging && b.isBeingDragged) {
//Let's see if the rectangle is inside the dropable area
if (b.x < c.width/2) {
myBoxes[i].x = b.xS;
myBoxes[i].y = b.yS;
myBoxes[i].draging = false;
b.isBeingDragged = false;
}
}
}
for (var i = 0; i< myDroppedBoxes.length; i++) {
var b = myDroppedBoxes[i];
if ( b.isBeingDragged) {
//Let's see if the rectangle is inside the dropable area
if (b.x>c.width/2) {
b.x = x;
b.y = y;
clubLegos(b);
plainTextMaker();
b.isBeingDragged = false;
}
else {
//No it's not, sending it back to its original spot
myDroppedBoxes.splice(i,1);
}
}
}
draw();
}
function clubLegos(b) {
// this loop is for checking that the box is lying near to which other box.
for(var j = 0; j < myDroppedBoxes.length; j++) {
var z = myDroppedBoxes[j];
if(!z.isBeingDragged) {
if(((x > z.x) && (x < (z.x + z.w))) && ((y > (z.y - 15)) && (y < (z.y + z.h + 10)))) {
b.x = z.x;
if( (y - z.y) >= 0) {
b.y = (z.y + z.h);
console.log("inside if " + y + " " + z.y);
}
else {
console.log("inside else " + y + " " + z.y);
b.y = (z.y - z.h);
}
}
}
}
}
function plainTextMaker() {
plainEnglishDiv = document.getElementById("plainEnglish");
plainEnglishDiv.innerHTML = "<h3>Here I am generating some plain text based on each drag and drop</h3>";
}
</script>
</html>
Here is the JS Fiddle for the same -
http://jsfiddle.net/akki166786/wa52f9pm/
Any help is greatly appreciated.
Thanks in advance.
Give each of your box objects something similar to Html's class.
This way you can drag every box with the same "class" simultaneously.
Add a club: property to each box.
// at top of app set a counter to make new clubs
var nextClub=0;
// each new box gets a unique "club"
function box(x,y,w,h,rgb,text) {
...
club:(nextClub++),
...
In clubLegos(b) when you're attaching dragged box b to another box z, also give the dropped box (b) & any member of (z)'s group a brand new club id:
// give the dropped box (b) & any member of (z)'s group a brand new club id
...if attaching b to z
b.club=nextClub;
for(var i=0;i<myBoxes.length;i++){
var bb=myBoxes[i];
if(bb.club==z.club){
bb.club=nextClub;
}
}
nextClub++;
This way, for example, if the mousedown has the user starting to drag a box with club==2, then you can add each myBoxes with club==2 into your dragging array and every box with club==2 will be dragged simultaneously.
I have a project I am trying to get an animated <canvas> working with Paper JS. What I am curious about is if there is anything built into PaperJS that allows the ability to detect interactivity between items (i.e. if a item is X distance from any other item on the layer). Here is what I have so far:
HTML
<canvas id="myCanvas" resize></canvas>
CSS
html, body{margin:0; padding: 0;}
#myCanvas{width: 100%; height: 100%;}
JS
$(function(){
var canvas = $('#myCanvas')[0];
paper.setup(canvas);
var viewSize = paper.view.size;
var itemCount = 20;
var theBall = new paper.Path.Rectangle({
point : [0,0],
size : 10,
fillColor : '#00a950',
});
var theBallSymbol = new paper.Symbol(theBall);
// Create and place symbol on view
for (var i = 1; i <= itemCount; i++) {
var center = paper.Point.random().multiply(viewSize);
var placedSymbol = theBallSymbol.place(center);
placedSymbol.scale(i / itemCount);
placedSymbol.data = {
origin : center,
direction : (Math.round(Math.random())) ? 'right' : 'left',
}
placedSymbol.onFrame = function(e){
var pathWidth = this.bounds.width * 20;
var center = this.data.origin;
var moveValue = this.bounds.width / 20;
if(this.data.direction == 'right'){
if(this.position.x < center.x + pathWidth){
this.position.x += moveValue;
} else{
this.position.x -= moveValue;
this.data.direction = 'left';
}
} else {
if(this.position.x > center.x - pathWidth){
this.position.x -= moveValue;
} else {
this.position.x += moveValue;
this.data.direction = 'right';
}
}
}
}
paper.view.onFrame = function (e){
// For entire view
for (var i = 0; i < itemCount; i++) {
var item = paper.project.activeLayer.children[i];
// I imagine I would need to do something here
// I tried a hitTest already, but I'm not sure
// that will give me the information I would need
}
}
});
JSFiddle
That part so far is working well. What I am curious about how I can do the following:
Whenever any given item (the squares) come within a distance of X between each other, create a line (path) between them
The idea is very similar to this page: http://panasonic.jp/shaver/lamdash/dna/
Any ideas would be greatly appreciated. Thanks!
Paper.js does not keep track of the inter-point distance between an item's center and all other items. The only way to gather that information is to manually loop through them.
In your case, I think it would be easiest to:
Create an array of lines
Only keep lines that might become shorter than the threshold value
Loop through the lines array on each onFrame() and adjust the opacity.
By only choosing lines that will come within a threshold value, you can avoid creating unnecessary paths that would slow the framerate. Without this, you'd be checking ~5 times as many items.
Here's a quick example:
$(function(){
var canvas = $('#myCanvas')[0];
paper.setup(canvas);
var viewSize = paper.view.size;
var itemCount = 60;
//setup arrays to change line segments
var ballArray = [];
var lineArray = [];
//threshold distance for lines
var threshold = Math.sqrt(paper.view.size.width*paper.view.size.height)/5;
var theBall = new paper.Path.Rectangle({
point : [0,0],
size : 10,
fillColor : '#00a950',
});
var theBallSymbol = new paper.Symbol(theBall);
// Create and place symbol on view
for (var i = 1; i <= itemCount; i++) {
var center = paper.Point.random().multiply(viewSize);
var placedSymbol = theBallSymbol.place(center);
placedSymbol.scale(i / itemCount);
placedSymbol.data = {
origin : center,
direction : (Math.round(Math.random())) ? 'right' : 'left',
}
// Keep each placedSymbol in an array
ballArray.push( placedSymbol );
placedSymbol.onFrame = function(e){
var pathWidth = this.bounds.width * 20;
var center = this.data.origin;
var moveValue = this.bounds.width / 20;
if(this.data.direction == 'right'){
if(this.position.x < center.x + pathWidth){
this.position.x += moveValue;
} else{
this.position.x -= moveValue;
this.data.direction = 'left';
}
} else {
if(this.position.x > center.x - pathWidth){
this.position.x -= moveValue;
} else {
this.position.x += moveValue;
this.data.direction = 'right';
}
}
}
}
// Run through every possible line
// Only keep lines whose length might become less than threshold
for (var i = 0; i < itemCount; i++) {
for (j = i + 1, point1 = ballArray[i].data.origin; j < itemCount; j++) {
if ( Math.abs(point1.y - ballArray[j].bounds.center.y) < threshold && Math.abs(point1.x - ballArray[j].data.origin.x) < 4 * threshold) {
var line = new paper.Path.Line( point1, ballArray[j].bounds.center ) ;
line.strokeColor = 'black';
line.strokeWidth = .5;
//note the index of the line's segments
line.point1 = i;
line.point2 = j;
if (line.length > 1.4 * threshold && ballArray[j].data.direction == ballArray[i].data.direction) {
line.remove();
}
else {
lineArray.push(line);
}
}
}
}
paper.view.onFrame = function (e){
// Update the segments of each line
// Change each line's opacity with respect to distance
for (var i = 0, l = lineArray.length; i < l; i++) {
var line = lineArray[i];
line.segments[0].point = ballArray[line.point1].bounds.center;
line.segments[1].point = ballArray[line.point2].bounds.center;
if(line.length < threshold) {
line.opacity = (threshold - line.length) / threshold;
}
else line.opacity = 0;
}
}
});
I need to adjust the script from http://javascript.about.com/library/blcvert.htm to change direction of scrolling to DOWN.
Could anybody help?
Of course, it would be also helpful if anybody knows/have some other script which produces the same effect.
Thanx
P.S. the script (in readable format is):
var imgAry1 = ['img1.png','img2.png'];
function startCloud() {
new mq('clouds', imgAry1, 380);
mqRotate(mqr);
}
$(document).ready(function() {
startCloud();
});
var mqr = [];
function mq(id, ary, heit) {
this.mqo=document.getElementById(id);
var wid = this.mqo.style.width;
this.mqo.onmouseout=function() { mqRotate(mqr); };
this.mqo.onmouseover=function() { clearTimeout(mqr[0].TO); };
this.mqo.ary=[];
var maxw = ary.length;
for (var i=0;i<maxw;i++) {
this.mqo.ary[i]=document.createElement('img');
this.mqo.ary[i].src=ary[i];
this.mqo.ary[i].style.position = 'absolute';
this.mqo.ary[i].style.top = (heit*i)+'px';
this.mqo.ary[i].style.height = heit+'px';
this.mqo.ary[i].style.width = wid;
this.mqo.appendChild(this.mqo.ary[i]);
}
mqr.push(this.mqo);
}
function mqRotate(mqr) {
if (!mqr) return;
for (var j=mqr.length - 1; j > -1; j--) {
maxa = mqr[j].ary.length;
for (var i=0;i<maxa;i++) {
var x = mqr[j].ary[i].style;
x.top=(parseInt(x.top,10)-1)+'px';
}
var y = mqr[j].ary[0].style;
if (parseInt(y.top,10)+parseInt(y.height,10)<0) {
var z = mqr[j].ary.shift();
z.style.top = (parseInt(z.style.top) + parseInt(z.style.height)*maxa) + 'px';
mqr[j].ary.push(z);
}
}
mqr[0].TO=setTimeout('mqRotate(mqr)',10);
}
On this line:
x.top=(parseInt(x.top,10)-1)+'px';
it says that you take x.top in pixels, parse out the number, subtract one and add the 'px' again. The element's position from top is decreased by 1 each time, so it goes up. All you need to do for it to go down is to add the one.
x.top=(parseInt(x.top,10)+1)+'px';
I also tested this hypothesis on the page you linked :)