html5 乒乓球(碰撞检测)

时间：2022-09-27 12:37:37

html5 乒乓球(碰撞检测)

演示地址

http://koking.8u.hanmandarin.com/html5/1.html

简单介绍

小球可以在方框内部*运动

可以通过方向键控制黑色砖块上下左右移动去与小球发生碰撞

代码实现

<!--

To change this template, choose Tools | Templates

and open the template in the editor.

-->

<!DOCTYPE html>

<html>

    <head>

        <title>乒乓球游戏</title>

        <meta http-equiv="Content-Type" content="text/html; charset=utf-8">

        <script>

            var ctx;

			var canvas;

			var ball_x=10;

			var ball_y=10;

			var ball_radius=10;

			var ball_vx=10;

			var ball_vy=8;

			var wall_x=30;

			var wall_y=40;

			var wall_width=30;

			var wall_height=60;

			var box_x=0;

			var box_y=0;

			var box_width=300;

			var box_height=300;

			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;

			var unit=10;

                        function intersect(sx, sy, fx, fy, cx, cy, rad)

                        {

                            var dx;

                            var dy;

                            var t;

                            var rt;

                            dx = fx - sx;

                            dy = fy - sy;

                            t = 0.0 - (((sx - cx) * dx + (sy - cy) * dy) / (dx * dx + dy * dy));

                            if (t < 0.0)

                            {

                                t = 0.0;

                            }

                            else if (t > 1.0)

                                t = 1.0;

                            var dx1 = (sx + t * dx) - cx;

                            var dy1 = (sy + t * dy) - cy;

                            var rt = dx1 * dx1 + dy1 * dy1;

                            if (rt < rad * rad)

                                return true;

                            else

                                return false;

                        }

			function move_ball()

			{

				ball_x=ball_x+ball_vx;

				ball_y=ball_y+ball_vy;

				if(ball_x<bound_left)

				{

					ball_x=bound_left;

					ball_vx=-ball_vx;

				}

				if(ball_x>bound_right)

				{

					ball_x=bound_right;

					ball_vx=-ball_vx;

				}

				if(ball_y<bound_top)

				{

					ball_y=bound_top;

					ball_vy=-ball_vy;

				}

				if(ball_y>bound_bottom)

				{

					ball_y=bound_bottom;

					ball_vy=-ball_vy;

				}

                                //撞到上边

                                if(intersect(wall_x,wall_y,wall_x+wall_width,wall_y+wall_height,ball_x,ball_y,ball_radius))

                                {

                                    ball_y=wall_y-ball_radius;

                                    ball_vy=-ball_vy;

                                }

                                //撞到左边

                                 if(intersect(wall_x,wall_y,wall_x,wall_y+wall_height,ball_x,ball_y,ball_radius))

                                {

                                    ball_x=wall_x-ball_radius;

                                    ball_vx=-ball_vx;

                                }

                                //撞到右边

                                 if(intersect(wall_x+wall_width,wall_y,wall_x+wall_width,wall_y+wall_height,ball_x,ball_y,ball_radius))

                                {

                                    ball_x=wall_x+wall_width+ball_radius;

                                    ball_vx=-ball_vx;

                                }

                                //撞到下边

                                 if(intersect(wall_x,wall_y+wall_height,wall_x+wall_width,wall_y+wall_height,ball_x,ball_y,ball_radius))

                                {

                                    ball_y=wall_y+wall_height+ball_radius;

                                    ball_vy=-ball_vy;

                                }

			}

			function move_wall(ev)

			{

				var keyCode;

				if(event==null)

				{

					keyCode=window.event.keyCode;

					window.event.preventDefault();

				}

				else

				{

					keyCode=event.keyCode;

					event.preventDefault();

				}

				switch(keyCode)

				{

					case 37://left;

					wall_x-=unit;

                                        if(wall_x<bound_left)

                                            wall_x=bound_left;

					break;

					case 38://up

					wall_y-=unit;

                                        if(wall_y<bound_top)

                                            wall_y=bound_top;

					break;

					case 39://right

					wall_x+=unit;

                                        if(wall_x+wall_width>bound_right)

                                            wall_x=bound_right-wall_width;

					break;

					case 40://down

					wall_y+=unit;

                                        if(wall_y+wall_height>bound_bottom)

                                            wall_y=bound_bottom-wall_height;

					break;

					default:

					break;

				}

			}

			function draw_all()

			{

                            ctx.beginPath();

				ctx.clearRect(box_x,box_y,box_width,box_height);

				ctx.fillStyle="rgb(255,0,0)";

				//ctx.lineWidth=ball_radius;

				ctx.arc(ball_x,ball_y,ball_radius,0,Math.PI*2,true);

				ctx.fill();//note

				ctx.fillStyle="rgb(0,0,0)";

				ctx.fillRect(wall_x,wall_y,wall_width,wall_height);

				ctx.strokeRect(box_x,box_y,box_width,box_height);

			}

			function init()

			{

				canvas=document.getElementById('canvas');

				ctx=canvas.getContext('2d');

				draw_all();

				setInterval(draw_all,100);

                                setInterval(move_ball,50);

				window.addEventListener('keydown',move_wall,false);//note

			}

         </script>

    </head>

    <body onLoad="init();">

        <canvas id="canvas" width="300" height="300"></canvas>

    </body>

</html>

难点

小球和砖块的碰撞检测以及碰撞处理

将砖块分解为4条线段

分别对小球和每条线段进行碰撞检测。

小球和线段的碰撞检测在另一篇文章

http://blog.csdn.net/foreverkoking/article/details/9453831

中有介绍。

相关文章