我是javascript的新手，我正在努力制作一款希望最终成为等距的游戏（我不在乎这么多，只要我知道如何）。我的代码是：
<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0"/>
<style>
canvas {
border:1px solid #d3d3d3;
background-color: #f1f1f1;
}
</style>
</head>
<body onload="startGame()">
<script>
var myGamePiece;
function startGame() {
myGamePiece = new component(30, 30, "blue", 225, 225);
myGameArea.start();
}
var myGameArea = {
canvas : document.createElement("canvas"),
start : function() {
this.canvas.width = 480;
this.canvas.height = 270;
this.context = this.canvas.getContext("2d");
document.body.insertBefore(this.canvas, document.body.childNodes[0]);
this.frameNo = 0;
this.interval = setInterval(updateGameArea, 20);
window.addEventListener('keydown', function (e) {
e.preventDefault();
myGameArea.keys = (myGameArea.keys || []);
myGameArea.keys[e.keyCode] = (e.type == "keydown");
})
window.addEventListener('keyup', function (e) {
myGameArea.keys[e.keyCode] = (e.type == "keydown");
})
},
stop : function() {
clearInterval(this.interval);
},
clear : function() {
this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
}
}
function component(width, height, color, x, y, type) {
this.type = type;
this.width = width;
this.height = height;
this.speed = 0;
this.angle = 0;
this.moveAngle = 0;
this.x = x;
this.y = y;
this.update = function() {
ctx = myGameArea.context;
ctx.save();
ctx.translate(this.x, this.y);
ctx.rotate(this.angle);
ctx.fillStyle = color;
ctx.fillRect(this.width / -2, this.height / -2, this.width, this.height);
ctx.restore();
}
this.newPos = function() {
this.angle += this.moveAngle * Math.PI / 180;
this.x += this.speed * Math.sin(this.angle);
this.y -= this.speed * Math.cos(this.angle);
}
}
function updateGameArea() {
myGameArea.clear();
myGamePiece.moveAngle = 0;
myGamePiece.speed = 0;
if (myGameArea.keys && myGameArea.keys[37]) {myGamePiece.x -=2; }
if (myGameArea.keys && myGameArea.keys[39]) {myGamePiece.x += 2; }
if (myGameArea.keys && myGameArea.keys[38]) {myGamePiece.y -= 1; }
if (myGameArea.keys && myGameArea.keys[40]) {myGamePiece.y += 1; }
if (myGameArea.keys && myGameArea.keys[32]) {myGamePiece.y -= 3;}
myGamePiece.newPos();
myGamePiece.update();
}
</script>
<p></p>
</body>
</html>
我主要从其他网站（http://www.w3schools.com/games/tryit.asp?filename=trygame_movement_keyboard）复制并粘贴。我想知道的是如何使它成为当玩家按下空间时，myGamePiece上下跳动似乎是跳跃;使它向上移动一定数量的空格，然后返回到之前的坐标。
答案 0 :(得分：1)
真实世界的V游戏世界。
游戏跳跃通常是非确定性的，这意味着你不确定游戏何时何地着陆。非常不喜欢现实生活。在现实生活中，一旦你跳跃，你降落的地点和时间都取决于重力和空气摩擦，除非你能飞，否则跳跃的结果就是宇宙。
在游戏世界中，这远非如此。跳线通常可以改变方向，双跳，做一些挂起时间，或组合加速力量打击。所有这些事情都可以随时发生，具体取决于用户的输入。游戏世界中的引力也不像真正的引力，有时候因为它们很重而有些东西下降得更快，有些东西需要一秒钟或者感觉到重力的影响。名单还在继续。
<强>降
但是所有这一切都表明游戏必须做的重要事情就是不像电梯一样下降。当你在自由落体时加速，你的速度每变化一次，当你跳起来减速时，当你跌倒时你会加速。我们有我们的位置y和我们的速度dy（delta y）来增加重力（g）我们在屏幕上移动（dy <0）或向下移动时为速度添加常数重力以相同的速率在同一方向上改变速度。
所以每一帧，加上重力dy += g然后将我们的速度加到我们的位置y + = dy。这就是一个非常简单的重力模拟，如果你在游戏框架中测量时间也是对真实重力的完美模拟（接近地球这样的大事）
因此，做跳跃的最佳方式，以及发挥作用的重力是逐帧进行。
让我们定义我们需要做什么跳跃。
一个简单的字符
var c = {
x : ?, // this character's position
y : ?,
dx : ?, // the amount to move per frame The players velocity in x and y
dy : ?,
w : ?, // the character's width and height
h : ?,
onGround : false, // a flag to indicate on the ground or not
}
以及一些环境信息
const GROUND_Y = canvas.height - 10; // where the ground is
const GRAVITY = 1; // in pixels per frame
然后每一帧我们更新角色，检查是否在地面上，如果没有施加重力并检查地面。
c.update = function(){
if(this.onGround){ // nothing to do but wait
}else{ // must be in the air
// Every frame the player accelerates down by the pull of gravity
// so increase the player y speed
this.dy += GRAVITY; // apply the gravity to the speed.
// now add the y speed to the y position
this.y += this.dy;
// Now we must check for the ground which if the player position x,y is for
// its center the ground will be half it's height away
if(this.y + (this.h / 2) > GROUND_Y){ // have we hit the ground
// yes stop downward motion
this.dy = 0;
// the speed may have put the character slightly below the ground
// so fix the postion so that it is correct
this.y = GROUND_Y - this.h /2; // set position to the ground - half its height
// And set the flag to indicate that the character is on the ground
this.onGround = true;
}
}
}
这就是重力照顾。
<强>跳
为了跳跃，我们施加一股力量使我们远离地面。这种力量只是暂时的，一旦我们没有任何东西可以推动，所以我们可以不再施力，它可以通过引力来降低我们的压力。由于重力已在上述功能中排序，我们需要做的就是应用跳跃力。
const JUMP_ACCELERATION = GRAVITY * 20; // the bigger this number the higher the jump
现在添加跳转功能
c.jump = function(){
// check if we can jump. That is are we on the ground
if(this.onGround){
// flag that we are no longer on the ground and left to the will of gravity
this.onGround = false;
// then apply the change in speed.
this.dy -= JUMP_ACCELERATION; // subtract jump accel from the speed
// to give a negative speed (up)
}
}
就是这样，引力函数将为你处理所有事情，所以你必须每帧调用一次c.update函数，每次跳转只调用一次跳跃函数。
JUMPING IT DEMO
单击鼠标跳转，一个非挑战性的飞扬它。
从旧项目中获取此演示显示了一个非常简单的跳跃角色。对象名称为it，您要查看的功能为it.update()，it.jump()和it.preJump()您想要的代码位于注释之间//答案代码
所有角色都可以跳跃，它可以跳跃，如果你点击并按住鼠标就可以跳得更高，然后释放跳跃。
/** ImageTools.js begin **/
var imageTools = (function () {
var tools = {
canvas : function (width, height) { // create a blank image (canvas)
var c = document.createElement("canvas");
c.width = width;
c.height = height;
return c;
},
createImage : function (width, height) {
var i = this.canvas(width, height);
i.ctx = i.getContext("2d");
return i;
},
loadImage : function (url, cb) {
var i = new Image();
i.src = url;
i.addEventListener('load', cb);
i.addEventListener('error', cb);
return i;
},
image2Canvas : function (img) {
var i = this.canvas(img.width, img.height);
i.ctx = i.getContext("2d");
i.drawImage(i, 0, 0);
return i;
},
drawSprite : function(image,spriteIndex, x, y, scale, ang, alpha) {
var w,h,spr;
spr = image.sprites[spriteIndex];
w = spr.w; h = spr.h;
ctx.globalAlpha = alpha;
ctx.setTransform(scale, 0, 0, scale, x, y);
ctx.rotate(ang);
ctx.drawImage(image, spr.x, spr.y, w, h, -w/2, -h/2, w, h);
},
drawSpriteS : function(image,spriteIndex, x, y, scale, scaleX, ang, alpha) {
var w,h,spr;
spr = image.sprites[spriteIndex];
w = spr.w; h = spr.h;
ctx.globalAlpha = alpha;
ctx.setTransform(scale * scaleX, 0, 0, scale, x, y);
ctx.rotate(ang);
ctx.drawImage(image, spr.x, spr.y, w, h, -w/2, -h/2, w, h);
},
hex2RGBA : function(hex){
if(typeof hex === "string"){
var str = "rgba(";
if(hex.length === 4 || hex.length === 5){
str += (parseInt(hex.substr(1,1),16) * 16) + ",";
str += (parseInt(hex.substr(2,1),16) * 16) + ",";
str += (parseInt(hex.substr(3,1),16) * 16) + ",";
if(hex.length === 5){
str += (parseInt(hex.substr(3,1),16) / 16);
}else{
str += "1";
}
return str + ")";
}
if(hex.length === 7 || hex.length === 8){
str += parseInt(hex.substr(1,2),16) + ",";
str += parseInt(hex.substr(3,2),16) + ",";
str += parseInt(hex.substr(5,2),16) + ",";
if(hex.length === 5){
str += (parseInt(hex.substr(7,2),16) / 255).toFixed(3);
}else{
str += "1";
}
return str + ")";
}
return "rgba(0,0,0,0)";
}
},
createGradient : function(ctx, type, x, y, xx, yy, colours){
var i,g,c;
var len = colours.length;
if(type.toLowerCase() === "linear"){
g = ctx.createLinearGradient(x,y,xx,yy);
}else{
g = ctx.createRadialGradient(x,y,xx,x,y,yy);
}
for(i = 0; i < len; i++){
c = colours[i];
if(typeof c === "string"){
if(c[0] === " #"){
c = this.hex2RGBA(c);
}
g.addColorStop(Math.min(1,i / (len -1)),c); // need to clamp top to 1 due to floating point errors causes addColorStop to throw rangeError when number over 1
}
}
return g;
},
};
return tools;
})();
/** ImageTools.js end **/
/** SimpleFullCanvasMouse.js begin **/
const CANVAS_ELEMENT_ID = "canv";
const U = undefined;
var w, h, cw, ch; // short cut vars
var canvas, ctx, mouse;
var globalTime = 0;
var globalTimeInt = 0;
var createCanvas, resizeCanvas, setGlobals;
var L = typeof log === "function" ? log : function(d){ console.log(d); }
createCanvas = function () {
var c,cs;
cs = (c = document.createElement("canvas")).style;
c.id = CANVAS_ELEMENT_ID;
cs.position = "absolute";
cs.top = cs.left = "0px";
cs.zIndex = 1000;
document.body.appendChild(c);
return c;
}
resizeCanvas = function () {
if (canvas === U) { canvas = createCanvas(); }
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
ctx = canvas.getContext("2d");
if (typeof setGlobals === "function") { setGlobals(); }
}
setGlobals = function(){
cw = (w = canvas.width) / 2; ch = (h = canvas.height) / 2;
if(it !== undefined){
it = createIt(cw,ch,sprites);
}
}
mouse = (function(){
function preventDefault(e) { e.preventDefault(); }
var mouse = {
x : 0, y : 0, w : 0, alt : false, shift : false, ctrl : false, buttonRaw : 0,
over : false, // mouse is over the element
bm : [1, 2, 4, 6, 5, 3], // masks for setting and clearing button raw bits;
mouseEvents : "mousemove,mousedown,mouseup,mouseout,mouseover,mousewheel,DOMMouseScroll".split(",")
};
var m = mouse;
function mouseMove(e) {
var t = e.type;
m.x = e.offsetX; m.y = e.offsetY;
if (m.x === U) { m.x = e.clientX; m.y = e.clientY; }
m.alt = e.altKey; m.shift = e.shiftKey; m.ctrl = e.ctrlKey;
if (t === "mousedown") { m.buttonRaw |= m.bm[e.which-1]; }
else if (t === "mouseup") { m.buttonRaw &= m.bm[e.which + 2]; }
else if (t === "mouseout") { m.buttonRaw = 0; m.over = false; }
else if (t === "mouseover") { m.over = true; }
else if (t === "mousewheel") { m.w = e.wheelDelta; }
else if (t === "DOMMouseScroll") { m.w = -e.detail; }
if (m.callbacks) { m.callbacks.forEach(c => c(e)); }
e.preventDefault();
}
m.addCallback = function (callback) {
if (typeof callback === "function") {
if (m.callbacks === U) { m.callbacks = [callback]; }
else { m.callbacks.push(callback); }
} else { throw new TypeError("mouse.addCallback argument must be a function"); }
}
m.start = function (element, blockContextMenu) {
if (m.element !== U) { m.removeMouse(); }
m.element = element === U ? document : element;
m.blockContextMenu = blockContextMenu === U ? false : blockContextMenu;
m.mouseEvents.forEach( n => { m.element.addEventListener(n, mouseMove); } );
if (m.blockContextMenu === true) { m.element.addEventListener("contextmenu", preventDefault, false); }
}
m.remove = function () {
if (m.element !== U) {
m.mouseEvents.forEach(n => { m.element.removeEventListener(n, mouseMove); } );
if (m.contextMenuBlocked === true) { m.element.removeEventListener("contextmenu", preventDefault);}
m.element = m.callbacks = m.contextMenuBlocked = U;
}
}
return mouse;
})();
var done = function(){
window.removeEventListener("resize",resizeCanvas)
mouse.remove();
document.body.removeChild(canvas);
canvas = ctx = mouse = U;
L("All done!")
}
resizeCanvas(); // create and size canvas
mouse.start(canvas,true); // start mouse on canvas and block context menu
window.addEventListener("resize",resizeCanvas); // add resize event
function drawText(text,x,y,size,col){
var f = size + "px Arial";
if(f !== ctx.font){
ctx.font = f;
}
ctx.fillStyle = col;
ctx.fillText(text,x,y);
}
function drawLoad(){
if(!resourcesReady || !canPlay){
drawText(message,cw,ch * 0.5, FONT_SIZE, MESSAGE_COL);
if (!canPlay && resourcesReady){
drawText("Try reloading the page.",cw,ch * 0.5 + FONT_SIZE + 8,Math.floor(FONT_SIZE /2) ,MESSAGE_COL);
}else{
drawText("Loading resources." ,cw,ch * 0.5 + FONT_SIZE + 8,Math.floor(FONT_SIZE /2) ,MESSAGE_COL);
}
}else{
if(message !== ""){
drawText(message,cw,ch * 0.5, FONT_SIZE, MESSAGE_COL);
}
}
}
const FONT = "px Arial"
const FONT_SIZE = Math.max(Math.floor(window.innerHeight/20),24)
ctx.textAlign = "center";
ctx.textBaseline = "middle";
function loaded(e){
if(e.type !== "error"){
this.sprites = [
{ x : 0, y : 0, w : 74, h : 116, },
{ x : 0, y : 126, w : 100, h : 113, },
{ x : 75, y : 0, w : 29, h : 42, },
{ x : 75, y : 43, w : 17, h : 22, },
{ x : 0, y : 249, w : 42, h : 18, },
{ x : 75, y : 66, w : 17, h : 15, },
{ x : 75, y : 82, w : 17, h : 12, },
{ x : 75, y : 95, w : 16, h : 9, },
{ x : 75, y : 105, w : 7, h : 7, },
{ x : 0, y : 268, w : 11, h : 5, },
]
resourcesReady = true;
canPlay = true;
it = createIt(cw,ch,this );
message = "";
return;
}
resourcesReady = true;
message = "LOAD FAILED!"
}
var it = null; // it is the character
var resourcesReady = false;
var canPlay = false;
var message = "Please Wait..."
const MESSAGE_COL = "white";
//var sprites = imageTools.loadImage("GreenIt.png",loaded )
var sprites = imageTools.loadImage("http://i.stack.imgur.com/ED6oC.png",loaded )
var background = imageTools.createImage(8,8);
background.ctx.fillStyle = imageTools.createGradient(ctx,"linear",0,0,8,8,["#0AF","#05A"]);
background.ctx.fillRect(0,0,8,8);
var ground = imageTools.createImage(8,32);
ground.ctx.fillStyle = imageTools.createGradient(ctx,"linear",0,0,8,32,["#0A0","#450","#754"]);
ground.ctx.fillRect(0,0,8,32);
ground.ctx.fillStyle = "black";
ground.ctx.fillRect(0,0,8,4);
const GROUND_OFFSET = 32;
const GRAV = 1;
var landed = false;
const MESSAGES = [
"Click mouse button to Jump",
"Click hold ... release to to add power to jump",
"Double click to double jump",
""
];
var messageCount = 0;
var fly = { // something to see
x : 0,
y : 0,
dx : 0,
dy : 0,
wait : 0,
onTheWall : false,
update : function(){
if(this.wait <= 0){
this.wait = Math.random() * 200+ 60;
this.onTheWall = Math.random() < 0.1 ? true : false;
if(this.onTheWall){
this.dx = 0;
this.dy = 0;
}else{
this.wait = Math.random() < 0.2 ? 10 : this.wait;
var x = (Math.random()-0.5) * 200;
var y = (Math.random()-0.5) * 200;
this.dx = (x - this.x) / this.wait;
this.dx = (y - this.y) / this.wait;
}
}else{
this.wait -= 1;
this.x += this.dx;
this.y += this.dy;
}
}
};
/*==============================================================================================
// Answer code
==============================================================================================*/
// info to define the character
const IT = {
body : 0, // sprite indexes
bodyFly : 1,
footDown : 2,
eyeOpen : 3,
foot : 4,
mouthOpen : 5,
eyeShut : 6,
mouthSmirk : 7,
eyeBall : 8,
mouth : 9, // sprite index end
grav : GRAV, // grav accel
maxJumpPower : 40,
minJump : 10,
jumpPower : 30, // mutiplys squat amount to give jump power
squatRate : 1, // how quick the squat is
squatResist : 0.8, // limits the amount of squat
landingBlinkTime : 30, // how long blink is on landing
blinkTime : 15, // how many frames to close eyes
blinkRate : 60 * 5, // 60 is one second . Time between blinks average
eyePos : {x : 0.13, y : -0.1}, // position as fraction of size
footPos : {x : 0.3, y : 0.5}, // position as fraction of size
lookAtGround : 1, // look ats
lookAtMouse : 2,
lookAtUser : 3,
lookAtFly : 4,
}
// Function updates the character
const updateIt = function(){
if(this.blink > 0){
this.blink -= 1;
}
if(this.blinkTimer > 0){
this.blinkTimer -= 1;
if(this.blinkTimer === 0){
this.blink = IT.blinkTime;
}
}else{
// the two randoms create a random number that has a gausian distrabution centered on 0.5
// this creates a more realistic set of numbers.
this.blinkTimer = Math.floor(IT.blinkRate * (Math.random() + Math.random())/2 + IT.blinkRate / 2);
this.lookAt = Math.random() < 0.33 ? IT.lookAtUser : (Math.random() < 0.5 ? IT.lookAtMouse : IT.lookAtFly);
}
if(!this.onGround){
this.squat = 0;
//-------------------------------------
// do gravity
this.dy += IT.grav;
this.y += this.dy;
this.x += this.dx;
if(this.dy > 2){
this.lookAt = IT.lookAtGround;
}
// check for the ground
if(this.y + this.tall / 2 > h - GROUND_OFFSET){
this.y = h - GROUND_OFFSET - this.tall / 2;
this.blink = Math.floor(IT.landingBlinkTime * (this.dy / 20));
this.blinkTimer = this.blink + 30;
this.squat = this.dy;
this.dy = 0;
this.onGround = true;
}
}else{
this.squat *= IT.squatResist;
}
}
// draw the character
const drawIt = function(){
var bod = IT.body;
var spr = this.img.sprites;
var eye = this.blink > 0 ? IT.eyeShut : IT.eyeOpen;
var foot = IT.foot;
var footBehind = false; // draw feet behind or infront of body
if(!this.onGround){
if(this.dy >= 0){
if(this.dy > 2){
bod = IT.bodyFly;
}
}else{
footBehind = true;
foot = IT.footDown;
}
}
var x = this.x ;
var y = this.y + this.squat;
var t = this.tall;
var f = this.fat;
if(footBehind){
if(!this.onGround){
var r = 1 - Math.min(1,-this.dy / 10);
imageTools.drawSpriteS(this.img,foot,x + f * IT.footPos.x,y - this.squat+ t * IT.footPos.y,1,-1,r,1);
imageTools.drawSprite(this.img,foot,x - f * IT.footPos.x,y - this.squat + t * IT.footPos.y,1,r,1);
}
}
imageTools.drawSprite(this.img,bod,x,y,1,0,1);
if(!footBehind){
if(this.onGround){
imageTools.drawSpriteS(this.img,foot,x + f * IT.footPos.x,y - this.squat+ t * IT.footPos.y,1,-1,0,1);
imageTools.drawSprite(this.img,foot,x - f * IT.footPos.x,y - this.squat + t * IT.footPos.y,1,0,1);
}else{
var r = this.dy / 10;
imageTools.drawSpriteS(this.img,foot,x + f * IT.footPos.x,y - this.squat+ t * IT.footPos.y,1,-1,r,1);
imageTools.drawSprite(this.img,foot,x - f * IT.footPos.x,y - this.squat + t * IT.footPos.y,1,r,1);
}
}
if(this.blink){
imageTools.drawSprite(this.img,eye,x + f * IT.eyePos.x,y + t * IT.eyePos.y,1,0,1);
imageTools.drawSpriteS(this.img,eye,x - f * IT.eyePos.x,y + t * IT.eyePos.y,1,-1,0,1);
}else{
imageTools.drawSprite(this.img,eye,x + f * IT.eyePos.x,y + t * IT.eyePos.y,1,0,1);
imageTools.drawSpriteS(this.img,eye,x - f * IT.eyePos.x,y + t * IT.eyePos.y,1,-1,0,1);
var eyeDir = 0;
var eyeDist = 0;
if(this.blink === 0){
if(this.lookAt === IT.lookAtGround){
eyeDir = Math.PI/2;
eyeDist = 0.3;
}else
if(this.lookAt === IT.lookAtUser){
eyeDir = 0;
eyeDist = 0;
}else
if(this.lookAt === IT.lookAtFly){
eyeDir = Math.atan2(fly.y, fly.x);
eyeDist = (Math.hypot(fly.y ,fly.x) / 200) * 0.3;
}else{
eyeDir = Math.atan2(mouse.y - this.y, mouse.x - this.x);
eyeDist = (Math.hypot(this.y - mouse.y,this.x - mouse.x) / (Math.min(w,h)/2)) * 0.3;
}
eyeDist = Math.max(-0.3, Math.min(0.3, eyeDist));
var ex,ey;
ex = Math.cos(eyeDir) * spr[IT.eyeOpen].w * eyeDist;
ey = Math.sin(eyeDir) * spr[IT.eyeOpen].h * eyeDist;
imageTools.drawSprite(this.img, IT.eyeBall, x + f * IT.eyePos.x + ex, y + t * IT.eyePos.y + ey,1,0,1);
imageTools.drawSprite(this.img, IT.eyeBall, x - f * IT.eyePos.x + ex, y + t * IT.eyePos.y + ey,1,0,1);
}
}
}
// While mouse is down squat and prep to jump
const preJump = function(){
this.squat += IT.squatRate;
this.jumpPower += 0.5;
this.jumpReady = true;
}
// when mouse released apply jump force
const jumpIt = function(){
this.dy = -IT.jumpPower * Math.min(IT.maxJumpPower,Math.max(IT.minJump,this.jumpPower))/IT.maxJumpPower;
this.jumpPower = 0;
this.jumpReady = false;
this.squat = 0;
this.onGround = false;
}
// creates a character
var createIt = function(x,y,img){
return {
img : img,
x : x, // position
y : y,
dx : 0, // deltat speed
dy : 0,
sqaut : 0, // for landing and pre jump slight squat
onGround : false,
jumpPower : 0,
blink : 0, // blink controls
blinkTimer : 0,
lookAt : "ground", /// where to look
jumpReady : false, // flags if ready to jump
tall : img.sprites[IT.body].h, // how tall
fat : img.sprites[IT.body].w, // how wide
draw : drawIt, // functions
update : updateIt,
jump : jumpIt,
squatF : preJump,
}
}
function display(){ // put code in here
ctx.setTransform(1,0,0,1,0,0); // reset transform
ctx.globalAlpha = 1; // reset alpha
ctx.drawImage(background,0,0,w,h)
ctx.drawImage(ground,0,h-GROUND_OFFSET,w,GROUND_OFFSET);
fly.update()
drawLoad();
if(canPlay){
if(messageCount < MESSAGES.length){
if(it.onGround && !landed){
landed = true;
message = MESSAGES[messageCount];
messageCount += 1;
}
}
if(mouse.buttonRaw & 1){
it.squatF();
}else{
if(it.jumpReady){
it.jump();
landed = false;
}
}
it.update();
it.draw();
}
//ctx.clearRect(0,0,w,h);
}
/*==============================================================================================
// Answer End
==============================================================================================*/
function update(timer){ // Main update loop
globalTimeInt = Math.floor(globalTime = timer);
display(); // call demo code
// continue until mouse right down
if (!(mouse.buttonRaw & 4)) { requestAnimationFrame(update); } else { done(); }
}
requestAnimationFrame(update);
/** SimpleFullCanvasMouse.js end **/
答案 1 :(得分：0)
我建议您查看我遵循的this (part 1)和this(part 2)教程。
你的跳跃＆＃34;动画只是归结为创建jump函数，该函数为对象设置最大跳转高度，并将布尔值设置为var jumping = true。只要你的角色是＆＃34;跳跃＆＃34;你增加角色的y位置。
一旦达到理想的高度，创建一个相反的land函数。
答案 2 :(得分：0)
创建一个Javascript setinterval，每隔20ms更新一次对象的高度。 每20秒设定高度=初始_高度+ u * t - （1/2） g t ^ 2 根据你的屏幕使用g = 9.8，u =某个常数。 t =时间流逝至今。这意味着，最初t = 0，在第一次更新时t = 20ms，在第二次更新时t = 40ms。
基本上，你是在模拟真实生活中的重力跳跃。