javascript/canvas5.html at master · nithinmohan/javascript · GitHub

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<html>
<head>
	<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
	<script type="text/javascript"
	src="jquery.js">
	</script>
	<script type="text/javascript">
	window.onload = function() {
		var vector2d=function(x,y){
			var vec={
				vx:x,
				vy:y,
				scale:function(scale){
					vec.vx*=scale;
					vec.vy*=scale;
				},
				add:function(vec2){
					vec.vx*=vec2.vx;
					vec.vy*=vec2.vy;
				},
				negate:function(){
					vec.vx=-vec.vx;
					vec.vy=-vec.vy;
				},
				normalize:function(){
					len=vec.vx*vec.vx+vec.vy*vec.vy;
					if(len){
						vec.vx/=len;
						vec.vy/=len;
					}
					return len;
				},
				length:function(){
					return Math.sqrt(vec.vx*vec.vx+vec.vy*vec.vy);
				},
				lengthsq:function(){
					return vec.vx*vec.vx+vec.vy*vec.vy;
				},
				rotate: function (angle) {
					var vx = vec.vx,
					vy = vec.vy,
					cosVal = Math.cos(angle),
					sinVal = Math.sin(angle);
					vec.vx = vx * cosVal - vy * sinVal;
					vec.vy = vx * sinVal + vy * cosVal;
				},
// toString() is a utility function for displaying the vector as text,
// a useful debugging aid.
toString: function () {
	return '(' + vec.vx.toFixed(3) + ',' + vec.vy.toFixed(3) + ')';
}
};
return vec;
};
var gameObjects=[],
canvas=document.getElementById('canvas'),
ctx=canvas.getContext('2d');
var cannonBall=function(x,y,vector){
	var gravity=0;
	var that={
		x:x,
		y:y,
		removeMe:false,
		move:function(){
			vector.vy+=gravity;
			gravity+=.1;
			that.x =that.x+vector.vx;
			that.y =that.y+vector.vy;
			if(that.y>canvas.height-150)
				that.removeMe=true;
		},
		draw: function () {
			ctx.beginPath();
			ctx.arc(that.x, that.y, 5, 0, Math.PI * 2, true);
			ctx.fill();
			ctx.closePath();
		}
	};
	return that;
};
var cannon=function(x,y)
{
	var mx=0,
	my=0,
	angle=0,
	that={
		x:x,
		y:y,
		angle:0,
		removeMe:false,
		move:function(){
			//alert((my-that.y)/(mx-that.x));
			angle=Math.atan2((my-that.y),(mx-that.x));
		},
		draw:function()
		{
			ctx.save();
			ctx.lineWidth=2;
			ctx.translate(that.x,that.y);
			ctx.rotate(angle);
			ctx.strokeRect(0,-5,50,10);
			ctx.moveTo(0,0);
			ctx.beginPath();
			ctx.arc(0,0,15,0,Math.PI*2,true);
			ctx.fill();
			ctx.closePath();
			ctx.restore();
		}
	};
			// When mouse is clicked, fire a cannonball.
			canvas.onmousedown = function (event) {
			// Create a vector from cannon postion in direction of mouse.
			//alert(mx-that.x, my-that.y);
			var vec = vector2d(mx-that.x, -my-that.y);
			vec.normalize(); // Make it unit length.
			vec.scale(25); // Scale it up to 25 units per frame.
			// Create a new cannonball, and add it to the gameObjects list.
			gameObjects.push(cannonBall(that.x, that.y, vec));
		};
			// Keep a note of the mouse position over the canvas.
			canvas.onmousemove = function (event) {
				var bb = canvas.getBoundingClientRect();
				mx = (event.clientX - bb.left);
				my = (event.clientY - bb.top);
			};
			return that;
		};
		var drawSkyAndGrass = function (){
			ctx.save();
// Set transparency.
ctx.globalAlpha = 0.4;
// Create a CanvasGradient object in linGrad.
// The gradient line is defined from the top to the bottom of the canvas.
var linGrad = ctx.createLinearGradient(0, 0, 0, canvas.height);
// Start off with sky blue at the top.
linGrad.addColorStop(0, '#00BFFF');
// Fade to white in the middle.
linGrad.addColorStop(0.5, 'white');
// Green for the top of the grass.
linGrad.addColorStop(0.5, '#55dd00');
// Fade to white at the bottom.
linGrad.addColorStop(1, 'white');
// Use the CanvasGradient object as the fill style.
ctx.fillStyle = linGrad;
// Finally, fill a rectangle the same size as the canvas.
ctx.fillRect(0, 0, canvas.width, canvas.height);
ctx.restore();
};
// Add an initial cannon to the game objects list.
gameObjects.push(cannon(50,canvas.height-150));
			var vec = vector2d(12, -15);
			gameObjects.push(cannonBall(30, 300, vec));
// This is the main loop that moves and draws everything.
setInterval( function() {
	drawSkyAndGrass();
	//alert(gameObjects.length);
// Here, we loop through all the object in the gameObjects[]
// Array. As each object is found, it is drawn, moved, and then
// added to the gameObjectsFresh[] array,UNLESS it has its removeMe flag
// set. gameObjectsFresh[] is then copied into gameObjects[] ready for
// the next frame. gameObjects[] will now not contain any removed
// objects, and they will disappear, as nothing references them anymore.
gameObjectsFresh = [];
for(var i=0;i<gameObjects.length;i++) {
	gameObjects[i].move();
	gameObjects[i].draw();
	if ( gameObjects[i].removeMe === false) {
		gameObjectsFresh.push(gameObjects[i]);
	}
};
gameObjects = gameObjectsFresh;
},30);
};
</script>
</head>
<body>
	<canvas id = "canvas" width = "640" height = "480" style="border:1px solid">
		No HTML5 Canvas detected!
	</canvas>
</body>
</html>