[英]HTML5 Canvas 2D Frameworks focusing on collision detection and physics
[英]HTML5 Canvas - Collision with ball physics glitch
我正在使用牛頓方程來制作我目前正在研究的這個程序中的球,當它們相互碰撞時會“分裂”,但有時它們會相互卡住,這會造成很多麻煩。
.
這是我的代碼:
<center>
<canvas id="canvas" style="border: 2px solid black; cursor: crosshair;" width="1000" height="500"></canvas>
</center>
<script>
var canvas = document.getElementById("canvas")
var ctx = canvas.getContext("2d")
var w = canvas.width
var h = canvas.height
var ball = []
var gravity = 0.3
var force = 0.2
var mouse = {
d: false,
x1: 0,
y1: 0,
x2: 0,
y2: 0,
}
window.onmousedown = function(e) {
mouse.d = true
mouse.x1 = mouse.x2 = e.pageX - canvas.getBoundingClientRect().left
mouse.y1 = mouse.y2 = e.pageY - canvas.getBoundingClientRect().top
}
window.onmousemove = function(e) {
if (mouse.d) {
mouse.x2 = e.pageX - canvas.getBoundingClientRect().left
mouse.y2 = e.pageY - canvas.getBoundingClientRect().top
} else {
mouse.x1 = mouse.x2 = e.pageX - canvas.getBoundingClientRect().left
mouse.y1 = mouse.y2 = e.pageY - canvas.getBoundingClientRect().top
}
}
window.onmouseup = function() {
if (mouse.d) {
mouse.d = false
var dx = (mouse.x1 - mouse.x2);
var dy = (mouse.y1 - mouse.y2);
var mag = Math.sqrt(dx * dx + dy * dy);
ball.push({
x: mouse.x1,
y: mouse.y1,
r: Math.floor(Math.random() * 20) + 10,
vx: dx / mag * -(mag * force),
vy: dy / mag * -(mag * force),
b: 0.7,
})
}
}
document.onselectstart = function() {return false}
document.oncontextmenu = function() {return false}
setInterval(update, 1000 / 60)
function update() {
ctx.clearRect(0, 0, w, h)
ctx.beginPath()
ctx.moveTo(mouse.x1, mouse.y1)
ctx.lineTo(mouse.x2, mouse.y2)
ctx.stroke()
ctx.closePath()
for (i = 0; i < ball.length; i++) {
ball[i].vy += gravity
ball[i].x += ball[i].vx
ball[i].y += ball[i].vy
if (ball[i].x > w - ball[i].r) {
ball[i].x = w - ball[i].r
ball[i].vx *= -ball[i].b
}
if (ball[i].x < ball[i].r) {
ball[i].x = ball[i].r
ball[i].vx *= -ball[i].b
}
if (ball[i].y > h - ball[i].r) {
ball[i].y = h - ball[i].r
ball[i].vy *= -ball[i].b
}
if (ball[i].y < ball[i].r) {
ball[i].y = ball[i].r
ball[i].vy *= -ball[i].b
}
for (j = i + 1; j < ball.length; j++) {
var dx = ball[i].x - ball[j].x
var dy = ball[i].y - ball[j].y
var dist = Math.sqrt(dx * dx + dy * dy)
if (Math.abs(dx) + Math.abs(dy) != 0 && dist <= ball[i].r + ball[j].r) {
var angle = Math.atan2(dy, dx)
var sp1 = Math.sqrt(ball[i].vx*ball[i].vx + ball[i].vy*ball[i].vy);
var sp2 = Math.sqrt(ball[j].vx*ball[j].vx + ball[j].vy*ball[j].vy);
var dir1 = Math.atan2(ball[i].vy, ball[i].vx);
var dir2 = Math.atan2(ball[j].vy, ball[j].vx);
var vx1 = sp1 * Math.cos(dir1 - angle);
var vy1 = sp1 * Math.sin(dir1 - angle);
var vx2 = sp2 * Math.cos(dir2 - angle);
var vy2 = sp2 * Math.sin(dir2 - angle);
var fvx1 = ((ball[i].r - ball[j].r) * vx1 + (2 * ball[j].r) * vx2) / (ball[i].r + ball[j].r);
var fvx2 = ((2 * ball[i].r) * vx1 + (ball[j].r - ball[i].r) * vx2) / (ball[i].r + ball[j].r);
var fvy1 = vy1;
var fvy2 = vy2;
ball[i].vx = Math.cos(angle) * fvx1 + Math.cos(angle + Math.PI/2) * fvy1;
ball[i].vy = Math.sin(angle) * fvx1 + Math.sin(angle + Math.PI/2) * fvy1;
ball[j].vx = Math.cos(angle) * fvx2 + Math.cos(angle + Math.PI/2) * fvy2;
ball[j].vy = Math.sin(angle) * fvx2 + Math.sin(angle + Math.PI/2) * fvy2;
}
}
ctx.beginPath()
ctx.arc(ball[i].x, ball[i].y, ball[i].r, 0, Math.PI * 2, false)
ctx.fillStyle = "black"
ctx.fill()
ctx.closePath()
}
}
</script>
當你產生了很多球並且它們的速度很快時,就會發生這種情況:
為什么? 任何人都知道我該如何解決這個問題?
你的解決方案似乎只有基於速度的懲罰力。 這允許球體穿透,當任何球體沒有速度時,它們都不會試圖固定穿透。 要解決此問題,您需要添加基於位置的懲罰。 一個非常簡單的解決方案是使用彈簧。 計算穿透長度並使用胡克定律將相交的球體彼此推開。
最好的解決方案是使用隱式聯系解算算法。 這允許更加僵硬的接觸,但是算法更加復雜。 我建議你使用2D物理引擎來獲得快速和良好的結果: Box2D的JavaScript端口似乎最常用。
我非常關注@ schteppe的答案。 我想在這里告訴你這個鏈接: http : //www.paulirish.com/2011/requestanimationframe-for-smart-animating/
看看“我為什么要用它?” 部分。 它可能會對你的問題的答案有一些暗示,即你的代碼究竟是什么問題。
順便說一句,我也一直試圖使你的代碼工作,但沒有實質性的結果。 你可以在這里查看我的小提琴(我從你的復制品): http : //jsfiddle.net/sukhmeetsd/joqpqp49/
var canvas = document.getElementById("canvas")
var ctx = canvas.getContext("2d")
var w = canvas.width
var h = canvas.height
var d = 5; //distance to move on collision
var ball = []
var gravity = 0.3
var force = 0.2
var mouse = {
d: false,
x1: 0,
y1: 0,
x2: 0,
y2: 0,
}
window.onmousedown = function (e) {
mouse.d = true
mouse.x1 = mouse.x2 = e.pageX - canvas.getBoundingClientRect().left
mouse.y1 = mouse.y2 = e.pageY - canvas.getBoundingClientRect().top
}
window.onmousemove = function (e) {
if (mouse.d) {
mouse.x2 = e.pageX - canvas.getBoundingClientRect().left
mouse.y2 = e.pageY - canvas.getBoundingClientRect().top
} else {
mouse.x1 = mouse.x2 = e.pageX - canvas.getBoundingClientRect().left
mouse.y1 = mouse.y2 = e.pageY - canvas.getBoundingClientRect().top
}
}
window.onmouseup = function () {
if (mouse.d) {
mouse.d = false
var dx = (mouse.x1 - mouse.x2);
var dy = (mouse.y1 - mouse.y2);
var mag = Math.sqrt(dx * dx + dy * dy);
ball.push({
x: mouse.x1,
y: mouse.y1,
r: Math.floor(Math.random() * 20) + 10,
vx: dx / mag * -(mag * force),
vy: dy / mag * -(mag * force),
b: 0.7,
})
}
}
function getRandomColor() {
var letters = '0123456789ABCDEF'.split('');
var color = '#';
for (var i = 0; i < 6; i++ ) {
color += letters[Math.floor(Math.random() * 16)];
}
return color;
}
document.onselectstart = function () {
return false
}
document.oncontextmenu = function () {
return false
}
setInterval(update, 1000/60)
function update() {
ctx.clearRect(0, 0, w, h)
ctx.beginPath()
ctx.moveTo(mouse.x1, mouse.y1)
ctx.lineTo(mouse.x2, mouse.y2)
ctx.stroke()
ctx.closePath()
for (i = 0; i < ball.length; i++) {
ball[i].vy += gravity
ball[i].x += ball[i].vx
ball[i].y += ball[i].vy
if (ball[i].x > w - ball[i].r) {
ball[i].x = w - ball[i].r
ball[i].vx *= -ball[i].b
}
if (ball[i].x < ball[i].r) {
ball[i].x = ball[i].r
ball[i].vx *= -ball[i].b
}
if (ball[i].y > h - ball[i].r) {
ball[i].y = h - ball[i].r
ball[i].vy *= -ball[i].b
}
if (ball[i].y < ball[i].r) {
ball[i].y = ball[i].r
ball[i].vy *= -ball[i].b
}
for (j = i + 1; j < ball.length; j++) {
var dx = ball[i].x - ball[j].x
var dy = ball[i].y - ball[j].y
var dist = Math.sqrt(dx * dx + dy * dy)
if (Math.abs(dx) + Math.abs(dy) != 0 && dist <= ball[i].r + ball[j].r) {
var angle = Math.atan2(dy, dx)
var sp1 = Math.sqrt(ball[i].vx * ball[i].vx + ball[i].vy * ball[i].vy);
var sp2 = Math.sqrt(ball[j].vx * ball[j].vx + ball[j].vy * ball[j].vy);
var dir1 = Math.atan2(ball[i].vy, ball[i].vx);
var dir2 = Math.atan2(ball[j].vy, ball[j].vx);
d = Math.ceil(ball[i].r+ball[j].r-dist)/2;
//moving them back
ball[i].x = ball[i].x - Math.cos(dir1)*d-1;
ball[i].y = ball[i].y - Math.sin(dir1)*d-1;
ball[j].x = ball[j].x + Math.cos(dir2)*d+1;
ball[j].y = ball[j].y + Math.sin(dir2)*d+1;
//Checking for distance again
/*dx = ball[i].x - ball[j].x;
dy = ball[i].y - ball[j].y;
dist = Math.sqrt(dx * dx + dy * dy);
if (Math.abs(dx) + Math.abs(dy) != 0 && dist <= ball[i].r + ball[j].r){
ball[i].x = ball[i].x + Math.cos(dir1)*2*d;
ball[i].y = ball[i].y + Math.sin(dir1)*d*2;
ball[j].x = ball[j].x - Math.cos(dir2)*d*2;
ball[j].y = ball[j].y - Math.sin(dir2)*d*2;
}*/
var vx1 = sp1 * Math.cos(dir1 - angle);
var vy1 = sp1 * Math.sin(dir1 - angle);
var vx2 = sp2 * Math.cos(dir2 - angle);
var vy2 = sp2 * Math.sin(dir2 - angle);
var fvx1 = ((ball[i].r - ball[j].r) * vx1 + (2 * ball[j].r) * vx2) / (ball[i].r + ball[j].r);
var fvx2 = ((2 * ball[i].r) * vx1 + (ball[j].r - ball[i].r) * vx2) / (ball[i].r + ball[j].r);
var fvy1 = vy1;
var fvy2 = vy2;
ball[i].vx = Math.cos(angle) * fvx1 + Math.cos(angle + Math.PI / 2) * fvy1;
ball[i].vy = Math.sin(angle) * fvx1 + Math.sin(angle + Math.PI / 2) * fvy1;
ball[j].vx = Math.cos(angle) * fvx2 + Math.cos(angle + Math.PI / 2) * fvy2;
ball[j].vy = Math.sin(angle) * fvx2 + Math.sin(angle + Math.PI / 2) * fvy2;
}
}
ctx.beginPath()
ctx.arc(ball[i].x, ball[i].y, ball[i].r, 0, Math.PI * 2, false)
ctx.fillStyle = getRandomColor();
ctx.fill();
ctx.closePath();
}
}
我的代碼不會讓球粘住但是它們處於不斷的攪拌狀態。 我正准備按照@schteppe的建議實施胡克定律,但后來我聽說過Box2d及其魔法。
只需使用重疊。 可以計算為兩個粒子的半徑之和與它們之間的距離之差。 下面的代碼是用 javascript 編寫的。 它在我的模擬中效果很好:
let overlap = particle1.r + particle2.r - distance(particle1, particle2);
particle1.x += 0.5*overlap;
particle2.x -= 0.5*overlap;
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