javascript - 球与矩形碰撞检测 Canvas javascript

标签 javascript html canvas

最近我开始学习 Canvas 动画，并一直在网上学习一些教程等。然而，在数学方面我已经开始触及一些界限。一个特殊的问题涉及一旦球击中 Canvas 内的 div 元素，就会反转球的 x 和 y 坐标。下面可以看到球的预期所需运动的图片表示。

cavas image

如您所见，我希望球的 x 和 y 坐标根据所触摸的 div 的一侧而变化。

目前，球确实在 Canvas 两侧正确弹起，并且也从主 div 的左侧和右侧正确弹起。然而，一旦球击中主分区的顶部或底部，逻辑就会崩溃。我的项目代码如下所示。

var canvas = document.querySelector('canvas');
    var content = document.querySelector('.main-content h1');
    
    var contentPosition = content.getBoundingClientRect();
    
    canvas.width = window.innerWidth;
    canvas.height = window.innerHeight;
    
    var radius = 10;
    var maxRadius = 20;
    
    var mouse = {
        x: undefined,
        y: undefined
    }
    
    var colour = [
        '#FF530D',
        '#E82C0C',
        '#FF0000',
        '#E80C7A',
        '#FF0DFF'
    ];
    
    window.addEventListener('mousemove', function(event){
    
       mouse.x = event.x;
       mouse.y = event.y;
    
    });
    
    //c = context
    var c = canvas.getContext('2d');
    
        function circle(x, y, dx, dy, radius){
    
            this.x = x;
            this.y = y;
            this.dx = dx;
            this.dy = dy;
            this.radius = radius;
            this.minRadius = Math.floor(Math.random() * 10 + 1);
            this.fillColour = colour[Math.floor(Math.random() * colour.length )];
    
            this.draw = function(){
    
                c.beginPath();
                c.arc(this.x, this.y, this.radius, 0, Math.PI*2);
                c.fillStyle = this.fillColour;
                c.fill();
                c.closePath();
            }
    
            this.update = function(){
    
                if(this.x + this.radius > innerWidth || this.x - this.radius < 0){
    
                   this.dx =- this.dx;
                }
    
                if(this.y + this.radius >= innerHeight || this.y - this.radius < 0){
    
                    this.dy =- this.dy;
                }
    
               if(this.x + this.radius > contentPosition.left && this.x - this.radius < contentPosition.right  && this.y + this.radius > contentPosition.top && this.y - this.radius < contentPosition.bottom){
                   this.dx =- this.dx;
                }
                
                if(this.x - mouse.x < 50 && (this.x - mouse.x) > -50
                    && this.y - mouse.y < 50 && this.y - mouse.y > -50){
    
                    if(this.radius < maxRadius){
                        this.radius +=2;
                    }
                }
                else if(this.radius > this.minRadius){
                    this.radius -= 2;
                }
    
                this.x += this.dx;
                this.y += this.dy;
    
                this.draw();
    
            }
    
    
        }
    
        circleArray = [];
    
        function getDistance(x1, y1, x2, y2){
    
            var xDistance = x2 - x1;
            var yDistance = y2 - y1;
    
            return Math.sqrt( Math.pow(xDistance, 2) + Math.pow(yDistance, 2));
        }
    
        function randomIntFromInterval(min,max)
        {
            return Math.floor(Math.random()*(max-min+1)+min);
        }
    
        function init(){
    
            for(i = 0; i < 100; i++){
    
                x = randomIntFromInterval(radius, innerWidth - radius);
                y = randomIntFromInterval(radius, innerHeight - radius);
    
                dx = (Math.random() - 0.5) * 2;
                dy = (Math.random() - 0.5) * 2;
    
    
                circleArray.push(new circle(x, y, dx, dy, radius));
            }
    
        }
    
        function animate(){
    
            requestAnimationFrame(animate);
            c.clearRect(0, 0, innerWidth, innerHeight);
    
            for(i = 0; i < circleArray.length; i++){
                circleArray[i].update();
            }
    
        }
    
        init();
        animate();
canvas {
    position: fixed;
    z-index: -9999;
}

body {
    margin: 0;
}

.main-content{
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
}

.main-content h1{
    font-weight: 700;
    font-size: 40px;
    text-shadow: 0 0 2px #464646;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <script src="http://code.jquery.com/jquery-3.3.1.slim.js" integrity="sha256-fNXJFIlca05BIO2Y5zh1xrShK3ME+/lYZ0j+ChxX2DA=" crossorigin="anonymous"></script>
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous">
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap-theme.min.css" integrity="sha384-rHyoN1iRsVXV4nD0JutlnGaslCJuC7uwjduW9SVrLvRYooPp2bWYgmgJQIXwl/Sp" crossorigin="anonymous">
    <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js" integrity="sha384-Tc5IQib027qvyjSMfHjOMaLkfuWVxZxUPnCJA7l2mCWNIpG9mGCD8wGNIcPD7Txa" crossorigin="anonymous"></script>
    <link rel="stylesheet" href="styles.css">
    <title>Canvas Test</title>
</head>
<body>
    <canvas></canvas>

   <div class="main-content">
       <h1 class="text-center">Example Text For Main Div</h1>
   </div>

    <script src="canvas.js"></script>
</body>
</html>

上面演示了整个工作逻辑。上面代码片段中检测与主 div 碰撞的代码如下。

 if(this.x + this.radius > contentPosition.left && this.x - this.radius < contentPosition.right  && this.y + this.radius > contentPosition.top && this.y - this.radius < contentPosition.bottom){
               this.dx =- this.dx;
            }

目前，一旦 div 的左侧或右侧被球击中，只有球的 x 坐标会发生变化。如果主 div 的顶部或底部被击中，我需要进行此调整以包括 Y 坐标的更改。

任何有关如何更正我的代码的建议或任何基于在线数学 Material 的知识(将指向答案)将不胜感激。

提前致谢

更新

根据答案中给出的代码更新圆投影路径

enter image description here

最佳答案

更新以通知网格问题已得到解决，并包含显示正在运行的解决方案的代码片段。

根据给定的图像，我假设圆圈始终从矩形外部开始，并且矩形始终与轴对齐。您可以根据相应的一对墙将 x 和 y 否定分开。下面的解决方案测试圆位于 div 一侧中间的时刻。

// Aliases to avoid thinking of offsetting positions
var circleTop = this.y - this.radius;
var circleBottom = this.y + this.radius;
var circleLeft = this.x - this.radius;
var circleRight = this.x + this.radius;

// For uniformity with circle
var rectTop = contentPosition.top;
var rectBottom = contentPosition.bottom;
var rectLeft = contentPosition.left;
var rectRight = contentPosition.right;

// Circle penetration on the div's left and right walls
if (((circleRight > rectLeft && circleLeft < rectLeft) ||
    (circleLeft < rectRight && circleRight > rectRight)) &&
    circleTop < rectBottom && circleBottom > rectTop) {

    this.dx = -this.dx;
}

// Circle penetration on the div's top and bottom walls
if (((circleBottom > rectTop && circleTop < rectTop) ||               
    (circleTop < rectBottom && circleBottom > rectBottom)) &&
    circleLeft < rectRight && circleRight > rectLeft) {

    this.dy = -this.dy;
}

以下是你的代码，移植了我的代码。

var canvas = document.querySelector('canvas');
    var content = document.querySelector('.main-content h1');
    
    var contentPosition = content.getBoundingClientRect();
    
    // For uniformity with circle
    var rectTop = contentPosition.top;
    var rectBottom = contentPosition.bottom;
    var rectLeft = contentPosition.left;
    var rectRight = contentPosition.right;
    
    canvas.width = window.innerWidth;
    canvas.height = window.innerHeight;
    
    var radius = 10;
    var maxRadius = 20;
    
    var mouse = {
        x: undefined,
        y: undefined
    }
    
    var colour = [
        '#FF530D',
        '#E82C0C',
        '#FF0000',
        '#E80C7A',
        '#FF0DFF'
    ];
    
    window.addEventListener('mousemove', function(event){
    
       mouse.x = event.x;
       mouse.y = event.y;
    
    });
    
    //c = context
    var c = canvas.getContext('2d');
    
        function circle(x, y, dx, dy, radius){
    
            this.x = x;
            this.y = y;
            this.dx = dx;
            this.dy = dy;
            this.radius = radius;
            this.minRadius = Math.floor(Math.random() * 10 + 1);
            this.fillColour = colour[Math.floor(Math.random() * colour.length )];
    
            this.draw = function(){
    
                c.beginPath();
                c.arc(this.x, this.y, this.radius, 0, Math.PI*2);
                c.fillStyle = this.fillColour;
                c.fill();
                c.closePath();
            }
    
            this.update = function(){
    
                if(this.x + this.radius > innerWidth || this.x - this.radius < 0){
    
                   this.dx =- this.dx;
                }
    
                if(this.y + this.radius >= innerHeight || this.y - this.radius < 0){
    
                    this.dy =- this.dy;
                }
    
                // Aliases to avoid thinking of offsetting positions
                var circleTop = this.y - this.radius;
                var circleBottom = this.y + this.radius;
                var circleLeft = this.x - this.radius;
                var circleRight = this.x + this.radius;

                // Circle penetration on the div's left and right walls
                if (((circleRight > rectLeft && circleLeft < rectLeft) ||
                    (circleLeft < rectRight && circleRight > rectRight)) &&
                    circleTop < rectBottom && circleBottom > rectTop) {

                    this.dx = -this.dx;
                }

                // Circle penetration on the div's top and bottom walls
                if (((circleBottom > rectTop && circleTop < rectTop) ||               
                    (circleTop < rectBottom && circleBottom > rectBottom)) &&
                    circleLeft < rectRight && circleRight > rectLeft) {

                    this.dy = -this.dy;
                }
                
                if(this.x - mouse.x < 50 && (this.x - mouse.x) > -50
                    && this.y - mouse.y < 50 && this.y - mouse.y > -50){
    
                    if(this.radius < maxRadius){
                        this.radius +=2;
                    }
                }
                else if(this.radius > this.minRadius){
                    this.radius -= 2;
                }
    
                this.x += this.dx;
                this.y += this.dy;
    
                this.draw();
    
            }
    
    
        }
    
        circleArray = [];
    
        function getDistance(x1, y1, x2, y2){
    
            var xDistance = x2 - x1;
            var yDistance = y2 - y1;
    
            return Math.sqrt( Math.pow(xDistance, 2) + Math.pow(yDistance, 2));
        }
    
        function randomIntFromInterval(min,max)
        {
            return Math.floor(Math.random()*(max-min+1)+min);
        }
    
        function init(){
    
            for(i = 0; i < 100; i++){
    
                x = randomIntFromInterval(radius, innerWidth - radius);
                y = randomIntFromInterval(radius, innerHeight - radius);
    
                dx = (Math.random() - 0.5) * 2;
                dy = (Math.random() - 0.5) * 2;
    
    
                circleArray.push(new circle(x, y, dx, dy, radius));
            }
    
        }
    
        function animate(){
    
            requestAnimationFrame(animate);
            c.clearRect(0, 0, innerWidth, innerHeight);
    
            for(i = 0; i < circleArray.length; i++){
                circleArray[i].update();
            }
    
        }
    
        init();
        animate();
canvas {
    position: fixed;
    z-index: -9999;
}

body {
    margin: 0;
}

.main-content{
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
}

.main-content h1{
    font-weight: 700;
    font-size: 40px;
    text-shadow: 0 0 2px #464646;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <script src="http://code.jquery.com/jquery-3.3.1.slim.js" integrity="sha256-fNXJFIlca05BIO2Y5zh1xrShK3ME+/lYZ0j+ChxX2DA=" crossorigin="anonymous"></script>
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous">
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap-theme.min.css" integrity="sha384-rHyoN1iRsVXV4nD0JutlnGaslCJuC7uwjduW9SVrLvRYooPp2bWYgmgJQIXwl/Sp" crossorigin="anonymous">
    <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js" integrity="sha384-Tc5IQib027qvyjSMfHjOMaLkfuWVxZxUPnCJA7l2mCWNIpG9mGCD8wGNIcPD7Txa" crossorigin="anonymous"></script>
    <link rel="stylesheet" href="styles.css">
    <title>Canvas Test</title>
</head>
<body>
    <canvas></canvas>

   <div class="main-content">
       <h1 class="text-center">Example Text For Main Div</h1>
   </div>

    <script src="canvas.js"></script>
</body>
</html>

需要注意的是，如果你的圆的速度(你的 this.dx 和 this.dy)足够大，并且你的 div 和圆足够小，那么圆可以穿过 div 的墙壁而不触发上面的碰撞条件。在视频游戏碰撞编程中，这个问题称为隧道，并且涉及更多减轻影响的算法，例如提前投影运动中的形状并针对其阴影进行测试。

对于更复杂的情况，您可能会发现一些更复杂的碰撞算法很有帮助，例如 Separating Axis Theorem (SAT 算法)当您的形状不再轴对齐时。

关于javascript - 球与矩形碰撞检测 Canvas javascript，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/48596327/

上一篇：javascript - 如何在每天的特定时间自动对 PHP 脚本执行 AJAX 请求？

下一篇：javascript - 将 Bootstrap 添加到 index.js

相关文章：

Javascript - 多个不等随机数生成器

javascript - 如何清除 Canvas 以进行重绘

javascript - 用另一个对象数组过滤一个对象数组

javascript - ReactJS - 循环遍历子对象并在父对象中显示前 10 个子对象

javascript - 我如何在运行时 "disable"require.js？

android - 如何使用 HTML 标签在 Android 的 EditText 中格式化文本

javascript - 在 Node 4.3 中使用 Buffer.from 时，TypeError Base64 不是一个函数

c# - 滚动单击不适用于 NavigationManager.NavigateTo，我无法使用 href，因为我需要 forceLoad 功能

html - 是否可以仅使用 css 展开和折叠表行/数据？

javascript - html5 canvas stroke twice 再次绘制第一笔画

©2024 IT工具网  联系我们