html5模拟平抛运动

<html>
<head>
<meta charset=utf-8>
<title>html5炮弹</title>
<script>
//box
var box_x=0;
var box_y=0;
var box_width=300;
var box_height=300;
//ball

var ball_x=10;
var ball_y=10;
var ball_radius=10;
var ball_vx=10;
var ball_vy=0;
//constant
var g=10;//note
var rate=0.9;
//bound
var bound_left=box_x+ball_radius;
var bound_right=box_x+box_width-ball_radius;
var bound_top=box_y+ball_radius;
var bound_bottom=box_y+box_height-ball_radius;

//context
var ctx;
function init()
{
	
	ctx=document.getElementById('canvas').getContext('2d');
	ctx.lineWidth=ball_radius;
	ctx.fillStyle="rgb(200,0,50)";
	move_ball();
	setInterval(move_ball,100);
}
function move_ball()
{
	ctx.clearRect(box_x,box_y,box_width,box_height);
	move_and_check();
	ctx.beginPath();
	ctx.arc(ball_x,ball_y,ball_radius,0,Math.PI*2,true);
	ctx.fill();
	ctx.strokeRect(box_x,box_y,box_width,box_height);
}
function move_and_check()
{
	var cur_ball_x=ball_x+ball_vx;
                  var temp=ball_vy;
	ball_vy=ball_vy+g;
	var cur_ball_y=ball_y+ball_vy+g/2;
	if(cur_ball_x<bound_left)
	{
		cur_ball_x=bound_left;
		ball_vx=-ball_vx*0.9;
                                     ball_vy=ball_vy*0.9;                 
	}
	if(cur_ball_x>bound_right)
	{
		cur_ball_x=bound_right;
		ball_vx=-ball_vx*0.9;
                                   ball_vy=ball_vy*0.9;                 
                                                
	}
	if(cur_ball_y<bound_top)
	{
		cur_ball_y=bound_top;
		ball_vy=-ball_vy*0.9;
                                    ball_vx=ball_vx*0.9;
	}
	if(cur_ball_y>bound_bottom)
	{
		cur_ball_y=bound_bottom;
		ball_vy=-ball_vy*0.9;
                                    ball_vx=ball_vx*0.9;
	}
	ball_x=cur_ball_x;
	ball_y=cur_ball_y;
}
</script>
</head>
<body onLoad="init()">
<canvas id="canvas" width="400" height="400"/>
</body>
</html>

html5模拟小球平抛运动过程。

posted @ 2013-07-24 19:21  爱生活,爱编程  阅读(324)  评论(0编辑  收藏  举报