首页 > 代码库 > 动画原理——碰撞检测
动画原理——碰撞检测
书籍名称：HTML5-Animation-with-JavaScript
书籍源码：https://github.com/lamberta/html5-animation1
1.两个物体
和判断鼠标是否在物体内相似，额外要多考虑鼠标方物体的半径。这不是准确的碰撞，它是假设物体在正方形基础上的简易方法。
01-object-hit-test.html
<!doctype html><html> <head> <meta charset="utf-8"> <title>Object Hit Test</title> <link rel="stylesheet" href="../include/style.css"> </head> <body> <header> Example from <a href="http://amzn.com/1430236655?tag=html5anim-20"><em>Foundation HTML5 Animation with JavaScript</em></a> </header> <canvas id="canvas" width="400" height="400"></canvas> <textarea id="log"></textarea> <aside>Drag circle with mouse.</aside> <script src="../include/utils.js"></script> <script src="./classes/ball.js"></script> <script> window.onload = function () { var canvas = document.getElementById(‘canvas‘), context = canvas.getContext(‘2d‘), log = document.getElementById(‘log‘), mouse = utils.captureMouse(canvas), ballA = new Ball(), ballB = new Ball(); ballA.x = canvas.width / 2; ballA.y = canvas.height / 2; (function drawFrame () { window.requestAnimationFrame(drawFrame, canvas); context.clearRect(0, 0, canvas.width, canvas.height); ballB.x = mouse.x; ballB.y = mouse.y; if (utils.intersects(ballA.getBounds(), ballB.getBounds())) { log.value = "Hit!"; } else { log.value = ‘‘; } ballA.draw(context); ballB.draw(context); //draw bounding boxes var boundsA = ballA.getBounds(), boundsB = ballB.getBounds(); context.strokeRect(boundsA.x, boundsA.y, boundsA.width, boundsA.height); context.strokeRect(boundsB.x, boundsB.y, boundsB.width, boundsB.height); }()); }; </script> </body></html>
utils.js
/** * Normalize the browser animation API across implementations. This requests * the browser to schedule a repaint of the window for the next animation frame. * Checks for cross-browser support, and, failing to find it, falls back to setTimeout. * @param {function} callback Function to call when it‘s time to update your animation for the next repaint. * @param {HTMLElement} element Optional parameter specifying the element that visually bounds the entire animation. * @return {number} Animation frame request. */if (!window.requestAnimationFrame) { window.requestAnimationFrame = (window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || window.msRequestAnimationFrame || window.oRequestAnimationFrame || function (callback) { return window.setTimeout(callback, 17 /*~ 1000/60*/); });}/** * ERRATA: ‘cancelRequestAnimationFrame‘ renamed to ‘cancelAnimationFrame‘ to reflect an update to the W3C Animation-Timing Spec. * * Cancels an animation frame request. * Checks for cross-browser support, falls back to clearTimeout. * @param {number} Animation frame request. */if (!window.cancelAnimationFrame) { window.cancelAnimationFrame = (window.cancelRequestAnimationFrame || window.webkitCancelAnimationFrame || window.webkitCancelRequestAnimationFrame || window.mozCancelAnimationFrame || window.mozCancelRequestAnimationFrame || window.msCancelAnimationFrame || window.msCancelRequestAnimationFrame || window.oCancelAnimationFrame || window.oCancelRequestAnimationFrame || window.clearTimeout);}/* Object that contains our utility functions. * Attached to the window object which acts as the global namespace. */window.utils = {};/** * Keeps track of the current mouse position, relative to an element. * @param {HTMLElement} element * @return {object} Contains properties: x, y, event */window.utils.captureMouse = function (element) { var mouse = {x: 0, y: 0, event: null}, body_scrollLeft = document.body.scrollLeft, element_scrollLeft = document.documentElement.scrollLeft, body_scrollTop = document.body.scrollTop, element_scrollTop = document.documentElement.scrollTop, offsetLeft = element.offsetLeft, offsetTop = element.offsetTop; element.addEventListener(‘mousemove‘, function (event) { var x, y; if (event.pageX || event.pageY) { x = event.pageX; y = event.pageY; } else { x = event.clientX + body_scrollLeft + element_scrollLeft; y = event.clientY + body_scrollTop + element_scrollTop; } x -= offsetLeft; y -= offsetTop; mouse.x = x; mouse.y = y; mouse.event = event; }, false); return mouse;};/** * Keeps track of the current (first) touch position, relative to an element. * @param {HTMLElement} element * @return {object} Contains properties: x, y, isPressed, event */window.utils.captureTouch = function (element) { var touch = {x: null, y: null, isPressed: false, event: null}, body_scrollLeft = document.body.scrollLeft, element_scrollLeft = document.documentElement.scrollLeft, body_scrollTop = document.body.scrollTop, element_scrollTop = document.documentElement.scrollTop, offsetLeft = element.offsetLeft, offsetTop = element.offsetTop; element.addEventListener(‘touchstart‘, function (event) { touch.isPressed = true; touch.event = event; }, false); element.addEventListener(‘touchend‘, function (event) { touch.isPressed = false; touch.x = null; touch.y = null; touch.event = event; }, false); element.addEventListener(‘touchmove‘, function (event) { var x, y, touch_event = event.touches[0]; //first touch if (touch_event.pageX || touch_event.pageY) { x = touch_event.pageX; y = touch_event.pageY; } else { x = touch_event.clientX + body_scrollLeft + element_scrollLeft; y = touch_event.clientY + body_scrollTop + element_scrollTop; } x -= offsetLeft; y -= offsetTop; touch.x = x; touch.y = y; touch.event = event; }, false); return touch;};/** * Returns a color in the format: ‘#RRGGBB‘, or as a hex number if specified. * @param {number|string} color * @param {boolean=} toNumber=false Return color as a hex number. * @return {string|number} */window.utils.parseColor = function (color, toNumber) { if (toNumber === true) { if (typeof color === ‘number‘) { return (color | 0); //chop off decimal } if (typeof color === ‘string‘ && color[0] === ‘#‘) { color = color.slice(1); } return window.parseInt(color, 16); } else { if (typeof color === ‘number‘) { color = ‘#‘ + (‘00000‘ + (color | 0).toString(16)).substr(-6); //pad } return color; }};/** * Converts a color to the RGB string format: ‘rgb(r,g,b)‘ or ‘rgba(r,g,b,a)‘ * @param {number|string} color * @param {number} alpha * @return {string} */window.utils.colorToRGB = function (color, alpha) { //number in octal format or string prefixed with # if (typeof color === ‘string‘ && color[0] === ‘#‘) { color = window.parseInt(color.slice(1), 16); } alpha = (alpha === undefined) ? 1 : alpha; //parse hex values var r = color >> 16 & 0xff, g = color >> 8 & 0xff, b = color & 0xff, a = (alpha < 0) ? 0 : ((alpha > 1) ? 1 : alpha); //only use ‘rgba‘ if needed if (a === 1) { return "rgb("+ r +","+ g +","+ b +")"; } else { return "rgba("+ r +","+ g +","+ b +","+ a +")"; }};/** * Determine if a rectangle contains the coordinates (x,y) within it‘s boundaries. * @param {object} rect Object with properties: x, y, width, height. * @param {number} x Coordinate position x. * @param {number} y Coordinate position y. * @return {boolean} */window.utils.containsPoint = function (rect, x, y) { return !(x < rect.x || x > rect.x + rect.width || y < rect.y || y > rect.y + rect.height);};/** * Determine if two rectangles overlap. * @param {object} rectA Object with properties: x, y, width, height. * @param {object} rectB Object with properties: x, y, width, height. * @return {boolean} */window.utils.intersects = function (rectA, rectB) { return !(rectA.x + rectA.width < rectB.x || rectB.x + rectB.width < rectA.x || rectA.y + rectA.height < rectB.y || rectB.y + rectB.height < rectA.y);};
动画原理——碰撞检测
声明：以上内容来自用户投稿及互联网公开渠道收集整理发布，本网站不拥有所有权，未作人工编辑处理，也不承担相关法律责任，若内容有误或涉及侵权可进行投诉： 投诉/举报 工作人员会在5个工作日内联系你，一经查实，本站将立刻删除涉嫌侵权内容。