[js高手之路]html5 canvas动漫教程 - 边界判别与小球

作者:分分快三计划

左侧界:只要判别小球的圆心x 假若低于小球的半径,那必然是遭遇了左侧界,我们就让小球的中央x等于小球的半径。

分分快三计划 1

透过canvas的为主点,不停的向四周发射小球,产生散弹的效果与利益. 

 1 <head>
 2     <meta charset='utf-8' />
 3     <style>
 4         #canvas {
 5             border: 1px dashed #aaa;
 6         }
 7     </style>
 8     <script src="./ball.js"></script>
 9     <script>
10         window.onload = function () {
11             var oCanvas = document.querySelector("#canvas"),
12                 oGc = oCanvas.getContext('2d'),
13                 width = oCanvas.width, height = oCanvas.height,
14                 ball = new Ball(width / 2, height / 2);
15                 ball.fill( oGc );
16             addEventListener("keydown", function (ev) {
17                 oGc.clearRect(0, 0, width, height);
18                 var oEvent = ev || event;
19                 switch (oEvent.keyCode) {
20                     case 37:
21                         ball.x -= 5;
22                         checkBorder();
23                         ball.fill(oGc);
24                         break;
25                     case 39:
26                         ball.x  = 5;
27                         checkBorder();
28                         ball.fill(oGc);
29                         break;
30                     case 38:
31                         ball.y -= 5;
32                         checkBorder();
33                         ball.fill(oGc);
34                         break;
35                     case 40:
36                         ball.y  = 5;
37                         checkBorder();
38                         ball.fill(oGc);
39                         break;
40                 }
41             }, false);
42             function checkBorder() {
43                 if ( ball.x < ball.radius ) { //碰到左边界
44                     ball.x = ball.radius;
45                 } else if ( ball.y < ball.radius ) { //碰到上边界
46                     ball.y = ball.radius;
47                 } else if ( ball.x > width - ball.radius ) { //碰到右边界
48                     ball.x = width - ball.radius;
49                 }else if ( ball.y > height - ball.radius ){
50                     ball.y = height - ball.radius;
51                 }
52             }
53         }
54     </script>
55 </head>
56 
57 <body>
58     <canvas id="canvas" width="1200" height="600"></canvas>
59 </body>
 1 <head>
 2     <meta charset='utf-8' />
 3     <style>
 4         #canvas {
 5             border: 1px dashed #aaa;
 6         }
 7     </style>
 8     <script src="./ball.js"></script>
 9     <script>
10         window.onload = function () {
11             var oCanvas = document.querySelector("#canvas"),
12                 oGc = oCanvas.getContext('2d'),
13                 width = oCanvas.width, height = oCanvas.height,
14                 ball = new Ball(width / 2, height / 2);
15             ball.fill(oGc);
16             addEventListener("keydown", function (ev) {
17                 oGc.clearRect(0, 0, width, height);
18                 var oEvent = ev || event;
19                 switch (oEvent.keyCode) {
20                     case 37:
21                         ball.x -= 5;
22                         checkBorder();
23                         ball.fill(oGc);
24                         break;
25                     case 39:
26                         ball.x  = 5;
27                         checkBorder();
28                         ball.fill(oGc);
29                         break;
30                     case 38:
31                         ball.y -= 5;
32                         checkBorder();
33                         ball.fill(oGc);
34                         break;
35                     case 40:
36                         ball.y  = 5;
37                         checkBorder();
38                         ball.fill(oGc);
39                         break;
40                 }
41             }, false);
42             function checkBorder() {
43                 if (ball.x < -ball.radius) { //完全超出左边界
44                     ball.x = width   ball.radius; //让球从右边出来
45                 } else if (ball.y < -ball.radius) { //完全超出上边界
46                     ball.y = height   ball.radius;//让球从下面出来
47                 } else if (ball.x > width   ball.radius) { //完全超出右边界
48                     ball.x = -ball.radius;//让球从左边出来
49                 } else if (ball.y > height   ball.radius) {//完全超出下边界
50                     ball.y = -ball.radius; //让球从上边出来
51                 }
52             }
53         }
54     </script>
55 </head>
56 
57 <body>
58     <canvas id="canvas" width="1200" height="600"></canvas>
59 </body>

 

小编们得以在以前的功底上,加上海重型机器厂力的震慑,达成喷泉的效率

 分分快三计划 2

本身不清楚你们有未有那样的误区:不停的向四周发射小球,那是或不是要不停的创始小球呢?假诺您那样想,程序固然写出来了,确定会卡死.

备注:本文后边的代码,假使加载了ball.js,那么请使用那篇作品[js高手之路] html5 canvas动漫教程 - 匀速运动的ball.js代码.

 1 <head>
 2     <meta charset='utf-8' />
 3     <style>
 4         #canvas {
 5             border: 1px dashed #aaa;
 6         }
 7     </style>
 8     <script src="./ball.js"></script>
 9     <script>
10         window.onload = function () {
11             var oCanvas = document.querySelector("#canvas"),
12                 oGc = oCanvas.getContext('2d'),
13                 width = oCanvas.width, height = oCanvas.height,
14                 balls = [], n = 50, gravity = 0.2;
15             function getRandColor() {
16                 return '#'   (function (color) {
17                     return (color  = '0123456789abcdef'[Math.floor(Math.random() * 16)]) && (color.length == 6) ? color : arguments.callee(color);
18                 })('');
19             }
20             for (var i = 0; i < n; i  ) {
21                 var ball = new Ball(width / 2, height / 2, 20, getRandColor());
22                 ball.vx = (Math.random() * 2 - 1) * 5;
23                 ball.vy = (Math.random() * 2 - 1) * 10;
24                 balls.push(ball);
25             }
26             (function move() {
27                 oGc.clearRect(0, 0, width, height);
28                 balls.forEach(function (ball) {
29                     if (ball.x < -ball.radius
30                         || ball.x > width   ball.radius
31                         || ball.y < -ball.radius
32                         || ball.y > height   ball.radius) {
33                         ball.x = width / 2;
34                         ball.y = height / 2;
35                         ball.vx = (Math.random() * 2 - 1) * 5;
36                         ball.vy = (Math.random() * 2 - 1) * 10;
37                     }
38                     ball.x  = ball.vx;
39                     ball.y  = ball.vy;
40                     ball.vy  = gravity;
41                     ball.fill(oGc);
42                 });
43                 requestAnimationFrame(move);
44             })();
45         }
46     </script>
47 </head>
48 
49 <body>
50     <canvas id="canvas" width="1200" height="600"></canvas>
51 </body>
 1 <head>
 2     <meta charset='utf-8' />
 3     <style>
 4         #canvas {
 5             border: 1px dashed #aaa;
 6         }
 7     </style>
 8     <script src="./ball.js"></script>
 9     <script>
10         window.onload = function () {
11             var oCanvas = document.querySelector("#canvas"),
12                 oGc = oCanvas.getContext('2d'),
13                 width = oCanvas.width, height = oCanvas.height,
14                 balls = [], n = 50;
15             function getRandColor() {
16                 return '#'   ( function( color ){
17                     return ( color  = '0123456789abcdef' [Math.floor( Math.random() * 16 )] ) && ( color.length == 6 ) ? color : arguments.callee( color );
18                 } )( '' );
19             }
20             for( var i = 0; i < n; i   ) {
21                 var ball = new Ball( width / 2, height / 2, 20, getRandColor() );
22                 ball.vx = Math.abs( ( Math.random() * 2 - 1 ) * 5 );
23                 ball.vy = ( Math.random() * 2 - 1 ) * 5;
24                 balls.push( ball );
25             }
26             (function move(){
27                 oGc.clearRect( 0, 0, width, height );
28                 balls.forEach( function( ball ){
29                     if ( ball.x < -ball.radius
30                         || ball.x > width   ball.radius
31                         || ball.y < -ball.radius
32                         || ball.y > height   ball.radius ) {
33                             ball.x = width / 2;
34                             ball.y = height / 2;
35                             ball.vx = Math.abs( ( Math.random() * 2 - 1 ) * 5 );
36                             ball.vy = ( Math.random() * 2 - 1 ) * 5;
37                     }
38                     ball.x  = ball.vx;
39                     ball.y  = ball.vy;
40                     ball.fill( oGc );
41                 } );
42                 requestAnimationFrame( move );
43             })();
44         }
45     </script>
46 </head>
47 <body>
48     <canvas id="canvas" width="1200" height="600"></canvas>
49 </body>

分分快三计划 3

本文,大家要做点有趣的功力,首先,来贰个简易的边际判别,所谓边界剖断:就是把物体的移动节制在多个限定内.大家先来三个归纳的实例,在canvas上生成三个小球,小球的启幕地方是在canvas的正中间,然后通过键盘的光景左右来移动小球之处,假如小球遭逢canvas的左手,那么无法再向左运动,别的方向同理.

生龙活虎体化的散弹效果:

完全的实例代码:

别的上上面界跟左右是同理。

要兑现那么些成效,只须求一个边际推断,就能够。

右侧界:只要剖断小球的圆心x 假如超过canvas的上涨的幅度减去小球的半径,那鲜明是遇上了侧边界,大家就让小球的大旨x等于canvas的大幅度减去小球的半径

若是小球向左运动,且完全出乎侧面界,我们就让他从左侧出来,若是小球向右运动,且完全超过侧面界,大家就让他从左边出来。上下方向同理

分分快三计划 4

还足以经过决定小球的vx, vy,便是x方向和y方向的快慢,来界定小球朝某一个倾向发射,上面包车型地铁事例,大家只让小球朝着x轴的侧边发射

那张图,望着是否更像喷泉?

实在大家得以只创建,一定数额的小球,比方( 50, 60. ...100 ),然后当这个小球,完全抢先的疆界的时候,再把那些小球的圆心( x, y )设定到最先始的岗位,再一次随机x和y方向的速度,就足以达到指标了, 说白了便是,这几个完全超过边界的小球,大家让他再一次回来最早之处,只是改动了她的颜色和进度,给人认为正是十三分发射小球之处接连不断的在发射小球

 1 <head>
 2     <meta charset='utf-8' />
 3     <style>
 4         #canvas {
 5             border: 1px dashed #aaa;
 6         }
 7     </style>
 8     <script src="./ball.js"></script>
 9     <script>
10         window.onload = function () {
11             var oCanvas = document.querySelector("#canvas"),
12                 oGc = oCanvas.getContext('2d'),
13                 width = oCanvas.width, height = oCanvas.height,
14                 balls = [], n = 50;
15             function getRandColor() {
16                 return '#'   ( function( color ){
17                     return ( color  = '0123456789abcdef' [Math.floor( Math.random() * 16 )] ) && ( color.length == 6 ) ? color : arguments.callee( color );
18                 } )( '' );
19             }
20             for( var i = 0; i < n; i   ) {
21                 var ball = new Ball( width / 2, height / 2, 20, getRandColor() );
22                 ball.vx = ( Math.random() * 2 - 1 ) * 5;
23                 ball.vy = ( Math.random() * 2 - 1 ) * 5;
24                 balls.push( ball );
25             }
26             (function move(){
27                 oGc.clearRect( 0, 0, width, height );
28                 balls.forEach( function( ball ){
29                     if ( ball.x < -ball.radius
30                         || ball.x > width   ball.radius
31                         || ball.y < -ball.radius
32                         || ball.y > height   ball.radius ) {
33                             ball.x = width / 2;
34                             ball.y = height / 2;
35                             ball.vx = ( Math.random() * 2 - 1 ) * 5;
36                             ball.vy = ( Math.random() * 2 - 1 ) * 5;
37                     }
38                     ball.x  = ball.vx;
39                     ball.y  = ball.vy;
40                     ball.fill( oGc );
41                 } );
42                 requestAnimationFrame( move );
43             })();
44         }
45     </script>
46 </head>
47 <body>
48     <canvas id="canvas" width="1200" height="600"></canvas>
49 </body>

散弹效果:

 

分界穿透:

 1 function checkBorder() {
 2     if ( ball.x < ball.radius ) { //碰到左边界
 3         ball.x = ball.radius;
 4     } else if ( ball.y < ball.radius ) { //碰到上边界
 5         ball.y = ball.radius;
 6     } else if ( ball.x > width - ball.radius ) { //碰到右边界
 7         ball.x = width - ball.radius;
 8     }else if ( ball.y > height - ball.radius ){
 9         ball.y = height - ball.radius;
10     }
11 }

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