js画布对象移动动画使用勾股定理

Question

我试图让一个对象移动到点击位置，就像在暗黑破坏神或现代moba游戏等rpg中，我需要找到一种方法来动画点击坐标，我找到了一种使用勾股定理的方法，我理解并自定义了代码在一定程度上，但有一个bug，球在动画的最后一直弹跳。我知道这是因为"行动"而发生的。变量和循环，但不能确切地理解为什么。

这是绘制对象

的函数

function drawPlayer() {
//
ctx.clearRect(0, 0, canvas.width, canvas.height);
ctx.beginPath();
ctx.arc(player.x, player.y, 12, 0, Math.PI*2);
ctx.fillStyle = 'white';
ctx.fill();
ctx.closePath();

//Calculate variables
let dx = player.newx - player.x;
let dy = player.newy - player.y;
let distance = Math.sqrt(dx*dx + dy*dy);
let moves = distance/player.speed;
let xunits = (player.newx - player.x)/moves;
let yunits = (player.newy - player.y)/moves;
if (moves > 0 ) {
moves--;
player.x += xunits;
player.y += yunits;
console.log(moves);
}
}

const canvas = document.getElementById('canvas1');
const ctx = canvas.getContext('2d');
canvas.addEventListener('click', e => {
setClickCoords(e);
drawPlayer();
})
canvas.width = 300;
canvas.height = 300;
const player = {
x: 0,
y: 0,
newx: 0,
newy: 0,
speed: 1,
radius: 15,
}
function drawPlayer() {
//Draw 
ctx.clearRect(0, 0, canvas.width, canvas.height);
ctx.beginPath();
ctx.arc(player.x, player.y, 12, 0, Math.PI * 2);
ctx.fillStyle = 'white';
ctx.fill();
ctx.closePath();
//Calculate variables
let dx = player.newx - player.x;
let dy = player.newy - player.y;
let distance = Math.sqrt(dx * dx + dy * dy);
let moves = distance / player.speed;
let xunits = (player.newx - player.x) / moves;
let yunits = (player.newy - player.y) / moves;
console.log(moves);
if (moves > 0) {
moves--;
player.x += xunits;
player.y += yunits;
console.log(moves);
}
}
function setClickCoords(e) {
player.newx = e.offsetX;
player.newy = e.offsetY;
document.getElementById('oldcoords').innerHTML = "old Coords " + player.x + " " + player.y;
document.getElementById('newcoords').innerHTML = "new Coords " + player.newx + " " + player.newy;
}

function gameLoop() {
window.setTimeout(gameLoop, 24);
drawPlayer()
}
gameLoop();

body {
background: black;
display: flex;
flex-direction: column;
}
#canvas1 {
border: 3px solid white;
top: 50%;
left: 50%;
position: absolute;
width: 300px;
height: 300px;
transform: translate(-50%, -50%);
}
#oldcoords,
#newcoords {
color: white;
font-size: 18px;
}

<span id="oldcoords"></span>
<span id="newcoords"></span>
<canvas id="canvas1"> </canvas>

Answer 1

检查moves是否在0 ~ 1之间。如果介于两者之间，把球移到想要的位置。目前，球在这个方向上走得太远了，必须在下一个动画中返回。

const canvas = document.getElementById('canvas1');
const ctx = canvas.getContext('2d');
canvas.addEventListener('click', e => {
setClickCoords(e);
drawPlayer();
})
canvas.width = 300;
canvas.height = 300;
const player = {
x: 0,
y: 0,
newx: 0,
newy: 0,
speed: 1,
radius: 15,
}
function drawPlayer() {
//Draw 
ctx.clearRect(0, 0, canvas.width, canvas.height);
ctx.beginPath();
ctx.arc(player.x, player.y, 12, 0, Math.PI * 2);
ctx.fillStyle = 'white';
ctx.fill();
ctx.closePath();
//Calculate variables
let dx = player.newx - player.x;
let dy = player.newy - player.y;
let distance = Math.sqrt(dx * dx + dy * dy);
let moves = distance / player.speed;
console.log(moves);
if (moves > 1) {
let xunits = (player.newx - player.x) / moves;
let yunits = (player.newy - player.y) / moves;
moves--;
player.x += xunits;
player.y += yunits;
console.log(moves);
} else if (moves > 0) {
moves = 0;
player.x = player.newx;
player.y = player.newy;
console.log(moves);
}
}
function setClickCoords(e) {
player.newx = e.offsetX;
player.newy = e.offsetY;
document.getElementById('oldcoords').innerHTML = "old Coords " + player.x + " " + player.y;
document.getElementById('newcoords').innerHTML = "new Coords " + player.newx + " " + player.newy;
}

function gameLoop() {
window.setTimeout(gameLoop, 24);
drawPlayer()
}
gameLoop();

body {
background: black;
display: flex;
flex-direction: column;
}
#canvas1 {
border: 3px solid white;
top: 50%;
left: 50%;
position: absolute;
width: 300px;
height: 300px;
transform: translate(-50%, -50%);
}
#oldcoords,
#newcoords {
color: white;
font-size: 18px;
}

<span id="oldcoords"></span>
<span id="newcoords"></span>
<canvas id="canvas1"> </canvas>