» Archive for the ‘JavaScript’ Category

Games & JavaScriptSunday, April 15th, 2007

Simplifying JavaScript game developer’s life… PART II

In the second part of dhtml game developing tutorial I want to present simple and very effective sprite animation technique. The Background positioning. 1. You need to have an image that contains all animation frames of your sprite.

  1. All frames should have the same size.
  2. Put the frames in a suitable sequence.First frame: Mario stands,
    Mario first, second, third step in right
    Mario first, second, third step in left.
  3. The start position of the next frame should be the end position of the last frame.For example:First frame position: (0,y)Second frame position: (0+width,y) Third frame position: ((0+width)*2,y) So the main formula will be: n- frame number (width*(n-1),y) Your frame have 32px width and you need the position of the fourth frame (32*3,y) = (96,y) Remember this work only when all frames have the same width.
  4. Save your image as a GIF or PNG format. The JPEG is recommended for large images. Do not use BMP format.

2. Create a layer with the width of the one frame:
position: absolute; // we’ll use left, top, right, bottom properties,
width: 32px; // only one frame will be visible,
height: 64px; // the height of frame,
left: 0; top: 0; // place it wherever you want,
background-image: url(mario.gif); // path to our image,
background-position: 0 0; // This is important, pointing at the first frame.

3. Animation: Now, we need to change/move the frame:
background-position: -(width*(n-1)) 0; so, which frame do you want? fourth? ok (32*(4-1))*(-1)= -96 background-position: -96px 0;

Why we multiply by -1? Fourth frame starts at 96px, but we see only frame at position 0, so we need to move the image 96px left. Rule is simple: Plus - when we need to move right, Minus - when we need to move left. Here is a simple demonstration of this technique in action, also I’m using collision detection and getValue functions described in the previous part of this tutorial…

Background positioning demo - Mario

CSS background-position Property

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Games & JavaScriptTuesday, March 13th, 2007

Simplifying JavaScript game developer’s life… PART I

Today I will present few JavaScript functions that might be helpful in game programming.
All these functions was tested in the latest Firefox, Opera and IE.

Let’s go:

1. getValue(val)

Converts numbers in a string value to the float/integer values. It is usefull when you have to manipulate on top,left,right,bottom or z-index attributes, but also it will work with any strings that contains numbers.

function getValue(val) {

if (val==”) return ”;

if (isNaN(val)) {

val=val.toLowerCase();

var num=[];

var ar=val.split(’ ‘);

for (i in ar) {

var b=(ar[i].substr(0,ar[i].length-2));

if (b==”) b=ar[i];

if (!isNaN(b)) num.push(parseFloat(b)); else num.push(ar[i]);

}

val=num.length>1 ? num : num[0];

} else val=parseFloat(val);

return val;

}

Example:

var el=document.getElementById(’test’);
el.style.margin=’10px 20px 30px 40px’;
var n=getValue(el.style.margin);
Result: n = Array [10,20,30,40]
n=getValue(el.style.margin)[0]+2;
Result: n=12; - not array
el.style.width=”10%”;
n=getValue(el.style.width);
Result: n=10; - not array
n=getValue(’foo bar 10px foo bar 1.3em foo bar 10%’);
Result: n= Array [10,1.3,10]

2. colorToRGB(val)

Converts a color string value to decimal rgb values.

function colorToRGB(val) {

val=val.toLowerCase();

var n=[];

if (val.indexOf(’rgb’)!=-1) {

n=((val.slice(val.indexOf(’rgb’)+4,val.indexOf(’)'))).replace(/ /g,”)).split(’,');

n[0]=parseInt(n[0]);

n[1]=parseInt(n[1]);

n[2]=parseInt(n[2]);

} else

if (val.indexOf(’#')!=-1) {

if ( val.charCodeAt(val.indexOf(’#')+4)==32 || isNaN(val.charCodeAt(val.indexOf(’#')+4))

) {

var x=val.split(”);

n[0]=parseInt(x[val.indexOf('#')+1]+x[val.indexOf('#')+1],16);

n[1]=parseInt(x[val.indexOf('#')+2]+x[val.indexOf('#')+2],16);

n[2]=parseInt(x[val.indexOf('#')+3]+x[val.indexOf('#')+3],16);

} else {

n[0]=parseInt(val.substr(val.indexOf(’#')+1,2),16);

n[1]=parseInt(val.substr(val.indexOf(’#')+3,2),16);

n[2]=parseInt(val.substr(val.indexOf(’#')+5,2),16);

}

} else

{

var col=[

'alicebluef0f8ff','antiquewhitefaebd7','aqua00ffff',

'aquamarine7fffd4','azuref0ffff','beigef5f5dc',

'bisqueffe4c4','black000000','blanchedalmondffebcd',

'blue0000ff','blueviolet8a2be2','browna52a2a',

'burlywooddeb887','cadetblue5f9ea0','chartreuse7fff00',

'chocolated2691e','coralff7f50','cornflowerblue6495ed',

'cornsilkfff8dc','crimsondc143c','cyan00ffff',

'darkblue00008b','darkcyan008b8b','darkgoldenrodb8860b',

'darkgraya9a9a9','darkgreen006400','darkkhakibdb76b',

'darkmagenta8b008b','darkolivegreen556b2f','darkorangeff8c00',

'darkorchid9932cc','darkred8b0000','darksalmone9967a',

'darkseagreen8fbc8f','darkslateblue483d8b','darkslategray2f4f4f',

'darkturquoise00ced1','darkviolet9400d3','deeppinkff1493',

'deepskyblue00bfff','dimgray696969','dodgerblue1e90ff',

'firebrickb22222','floralwhitefffaf0','forestgreen228b22',

'fuchsiaff00ff','gainsborodcdcdc','ghostwhitef8f8ff',

'goldffd700','goldenroddaa520','gray808080',

'green008000','greenyellowadff2f','honeydewf0fff0',

'hotpinkff69b4','indianredcd5c5c','indigo4b0082',

'ivoryfffff0','khakif0e68c','lavendere6e6fa',

'lavenderblushfff0f5','lawngreen7cfc00','lemonchiffonfffacd',

'lightblueadd8e6','lightcoralf08080','lightcyane0ffff',

'lightgoldenrodyellowfafad2','lightgrayd3d3d3','lightgreen90ee90',

'lightpinkffb6c1','lightsalmonffa07a','lightseagreen20b2aa',

'lightskyblue87cefa','lightslategray778899','lightsteelblueb0c4de',

'lightyellowffffe0','lime00ff00','limegreen32cd32',

'linenfaf0e6','magentaff00ff','maroon800000',

'mediumaquamarine66cdaa','mediumblue0000cd','mediumorchidba55d3',

'mediumpurple9370d8','mediumseagreen3cb371','mediumslateblue7b68ee',

'mediumspringgreen00fa9a','mediumturquoise48d1cc','mediumvioletredc71585',

'midnightblue191970','mintcreamf5fffa','mistyroseffe4e1',

'moccasinffe4b5','navajowhiteffdead','navy000080',

'oldlacefdf5e6','olive808000','olivedrab6b8e23',

'orangeffa500','orangeredff4500','orchidda70d6',

'palegoldenrodeee8aa','palegreen98fb98','paleturquoiseafeeee',

'palevioletredd87093','papayawhipffefd5','peachpuffffdab9',

'perucd853f','pinkffc0cb','plumdda0dd',

'powderblueb0e0e6','purple800080','redff0000',

'rosybrownbc8f8f','royalblue4169e1','saddlebrown8b4513',

'salmonfa8072','sandybrownf4a460','seagreen2e8b57',

'seashellfff5ee','siennaa0522d','silverc0c0c0',

'skyblue87ceeb','slateblue6a5acd','slategray708090',

'snowfffafa','springgreen00ff7f','steelblue4682b4',

'tand2b48c','teal008080','thistled8bfd8',

'tomatoff6347','turquoise40e0d0','violetee82ee',

'wheatf5deb3','whiteffffff','whitesmokef5f5f5',

'yellowffff00','yellowgreen9acd32'];

for (i in col) if (val.indexOf(col[i].substr(0,col[i].length-6))!=-1) break;

n=colorToRGB(’#'+col[i].substr(col[i].length-6));

}

return n;

}

Example:

var el=document.getElementById(’test’);
el.style.color=”#FFFFFF”;
var n=colorToRGB(el.style.color);
Result: n= Array [255,255,255];
el.style.background=”#666″;
var n=colorToRGB(el.style.background);
Result: n= Array [102,102,102];
el.style.border=”1px solid turquoise”;
var n=colorToRGB(el.style.border);
Result: n= Array [64,224,208]
el.style.color=”white”;
var n=colorToRGB(el.style.color);
Result: n= Array [255,255,255]

3. getLayerCrd(id)

Gets the current positions of first (X,Y) and opposite (X+width,Y+height) vertex of an element based on container coordinates.

function getLayerCrd(id) {

if (document.getElementById(id)) {

var n=[];

var obj=document.getElementById(id);

n[0]=obj.offsetLeft;

n[1]=obj.offsetTop;

n[2]=obj.offsetLeft+obj.offsetWidth;

n[3]=obj.offsetTop+obj.offsetHeight;

return n;

} else return -1;

}

Example of use:

var n=getLayer(’test’);
el.style.margin=’10px 20px 30px 40px’;
Result: n= Array [x,y,x+width,y+height]

Note: getLayerCrd(id) should be used with block objects.

4. colDetect(id1,id2)

Returns true if two objects overlapping each other. Simple collision detection based on object coordinates (getLayerCrd(id) function is required)

function colDetect(id1,id2) {

var n1=getLayerCrd(id1);

var n2=getLayerCrd(id2);

if ((n1!=-1) && (n2!=-1)) {

if ((((n1[2]>=n2[0]) && (n1[2]<=n2[2])) ||

((n1[0]<=n2[2]) && (n1[0]>=n2[0]))) &&

(((n1[3]>=n2[1]) && (n1[3]<=n2[3])) ||

((n1[1]<=n2[3]) && (n1[1]>=n2[1]))))

{ return true;} else return false;

} else return false;

}

Example of use:

var n=colDetect(’test1′,’test2′);
el.style.margin=’10px 20px 30px 40px’;
returns true or false

Note: Same as with getLayerCrd(id) - use with block objects. Both objects should be placed in the same container or you will have to modify the getLayerCrd(id) function for geting position based on page coordinates.

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Games & JavaScriptSunday, March 4th, 2007

c# to JavaScript and Space Invaders

Thanks to Zproxy I found something what is called JSC - C# to JavaScript.
JSC is a compiler (or a decompiler) and as the name points out JSC will helps you prepare the JavaScript applications in the C# language. See the project website for more details.

Also, Zproxy has made nice implementation of the Space Invaders, written in C# and precompiled to JavaScript by using mentioned compiler.

Space Invaders (JSC version)

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