I'm trying to make a simple interactive game where there are circles of different colours moving in the canvas and when the user clicks on the blue circles, it logs the number of clicks on the screen. When clicking circles with any other colour, the animation stops.
I'm very new to javascript but this is what I have for now. I've made a function with random coloured circles and a function with blue circles moving but I'm totally stuck on how to stop the animation when clicking on the function with a random coloured circles and logging the amount of clicks on the blue circles. If someone could help me move forward with it in any way (doesn't have to be the full thing), that would be awesome, thanks.
JS
var canvas;
var ctx;
var w = 1000;
var h = 600;
var colours = ["red", "blue"];
var allCircles = [];
for(var i=0; i<1; i++){
setTimeout(function(){console.log(i)},1000);
}
document.querySelector("#myCanvas").onclick = click;
createData(2);
createDataTwo(20);
setUpCanvas();
animationLoop();
function animationLoop(){
clear();
for(var i = 0; i<allCircles.length; i++){
circle(allCircles[i]);
forward(allCircles[i], 5)
turn(allCircles[i], randn(30));
collisionTestArray(allCircles[i],allCircles)
bounce(allCircles[i]);
}
requestAnimationFrame(animationLoop);
}
function collisionTestArray(o, a){
for(var i=0; i<a.length; i++){
if(o !=a[i]){
collision(o,a[i]);
}
}
}
function collision(o1,o2){
if(o1 && o2){
var differencex = Math.abs(o1.x-o2.x);
var differencey = Math.abs(o1.y-o2.y);
var hdif = Math.sqrt(differencex*differencex+differencey*differencey);
if(hdif<o1.r+o2.r){
if(differencex < differencey){
turn(o1, 180-2*o1.angle);
turn(o2, 180-2*o2.angle);
}else{
turn(o1, 360-2*o1.angle);
turn(o2, 360-2*o2.angle);
}
turn(o1, 180);
turn(o2, 180);
console.log("collision");
};
}
}
function click(event){
clear()
}
function bounce (o){
if(o.x > w || o.x < 0){
turn(o, 180-2*o.angle);
};
if(o.y > h || o.y < 0){
turn(o, 360-2*o.angle);
}
}
function clear(){
ctx.clearRect(0,0,w,h);
}
function stop (){
o1.changex = 0;
o1.changey = 0;
o2.changex = 0;
o2.changey = 0;
}
function circle (o){
var x = o.x;
var y = o.y;
var a = o.angle;
var d = o.d;
ctx.beginPath();
ctx.arc(o.x,o.y,o.r,0,2*Math.PI);
ctx.fillStyle = "hsla("+o.c+",100%,50%, "+o.a+")";
ctx.fill();
o.x = x;
o.y = y;
o.angle = a;
o.d = d;
}
function createData(num){
for(var i=0; i<num; i++){
allCircles.push({
"x": rand(w),
"changex": rand(10),
"y":rand(h),
"changex": rand(10),
"w": randn(w),
"h": randn(h),
"d": 1,
"a": 1,
"angle": 0,
"changle":15,
"c":216,
"r": 50
}
)
}
}
function createDataTwo(num){
for(var i=0; i<num; i++){
allCircles.push({
"x": rand(w),
"changex": rand(10),
"y":rand(h),
"changex": rand(10),
"w": randn(w),
"h": randn(h),
"d": 1,
"a": 1,
"angle": 0,
"changle":15,
"c":rand(90),
"r": 50
}
)
}
}
function turn(o,angle){
if(angle != undefined){
o.changle=angle;
};
o.angle+=o.changle;
}
function forward(o,d){
var changeX;
var changeY;
var oneDegree = Math.PI/180;
if(d != undefined){
o.d = d;
};
changeX= o.d*Math.cos(o.angle*oneDegree);
changeY = o.d*Math.sin(o.angle*oneDegree);
o.x+=changeX;
o.y+=changeY;
}
function randn(r){
var result = Math.random()*r - r/2
return result
}
function randi(r) {
var result = Math.floor(Math.random()*r);
return result
}
function rand(r){
return Math.random()*r
}
function setUpCanvas(){
canvas = document.querySelector("#myCanvas");
ctx = canvas.getContext("2d");
canvas.width = w;
canvas.height = h;
canvas.style.border = "5px solid orange"
ctx.fillStyle = "blue";
ctx.fillRect(0, 0, w, h);
}
console.log("assi4")
HTML
<html>
<head>
<link rel="stylesheet" type="text/css" href="../modules.css">
</head>
<body>
<div id="container">
<h1>Click the Blue Circles Only</h1>
<canvas id = "myCanvas"></canvas>
</div>
<script src="assi5.js"></script>
</body>
</html>
CSS
#container {
margin: auto;
width: 75%;
text-align: center;
}
You can use cancelAnimationFrame to stop the animation when a non-blue circle is clicked
You need to pass it a reference to the frame ID returned from requestAnimationFrame for it to work.
In order to tell if a circle was clicked, you need to check the coordinates of each circle against the coordinates of the click.
I have an example below if you had your blue circles in an array "blue", and other circles in array "other", the ID returned by requestAnimationFrame as "frame".
The check function returns the number of blue circles hit (the points scored) and if any other circles were hit, it stops the animation.
getCoords returns the coordinates of the click on the canvas from the click event.
canvas.addEventListener('click', event=>{
points += check(getCoords(event), blue, other, frame);
document.getElementById('points').textContent = points;
})
function check({x, y}, blue, other, frame) {
other.filter(circle=>circle.isWithin(x, y))
.length && cancelAnimationFrame(frame); // This is where animation stops
return blue.filter(circle=>circle.isWithin(x, y)).length;
}
function getCoords(event) {
const canvas = event.target;
const rect = canvas.getBoundingClientRect()
const x = event.clientX - rect.left;
const y = event.clientY - rect.top;
return { x, y };
}
I have an example that works below where I changed the circles to the result of a function rather than an inline object, and moved the functions you use on them into their own class. You don't have to do this, but I find it a lot easier to understand.
function main() {
const canvas = document.getElementById('canvas');
const context = canvas.getContext("2d");
const clear = () => context.clearRect(0, 0, canvas.width, canvas.height);
const blue = new Array(2).fill().map(() => new Circle(context, 216));
const other = new Array(10).fill().map(() => new Circle(context));
let circles = [...blue, ...other];
let frame = 0;
let points = 0;
// Move the circle a bit and check if it needs to bounce
function update(circle) {
circle.forward(1)
circle.turn(30, true)
circle.collisionTestArray(circles)
circle.bounce();
}
// Main game loop, clear canvas, update circle positions, draw circles
function loop() {
clear();
circles.filter(circle => circle.free).forEach(update);
circles.forEach(circle => circle.draw());
frame = requestAnimationFrame(loop);
}
loop();
canvas.addEventListener('click', event => {
points += check(getCoords(event), blue, other, frame, circles);
document.getElementById('points').textContent = points;
})
}
function check({ x, y }, blue, other, frame) {
other.filter(circle => circle.isWithin(x, y))
// .map(circle=>circle.toggle())
.length && cancelAnimationFrame(frame); // This is where animation stops
return blue.filter(circle => circle.isWithin(x, y)).length;
}
function getCoords(event) {
const canvas = event.target;
const rect = canvas.getBoundingClientRect()
const x = event.clientX - rect.left;
const y = event.clientY - rect.top;
return { x, y };
}
main();
function Circle(context, c) {
const randn = r => rand(r) - r / 2;
const randi = r => Math.floor(randi(r));
const rand = r => Math.random() * r;
// These are for easily stopping and starting a circle;
this.free = true;
this.stop = () => this.free = false;
this.release = () => this.free = true;
this.toggle = () => this.free = !this.free;
const {
width,
height
} = context.canvas;
// These are the same properties you were using in your code
this.x = rand(width);
this.changex = rand(10);
this.y = rand(height);
this.changey = rand(10);
this.w = randn(width);
this.h = randn(height);
this.d = 1;
this.a = 1;
this.angle = 0;
this.changle = 15;
this.c = c || rand(90); // This is the only difference between blue and other circles
this.r = 50;
// These next functions you had in your code, I just moved them into the circle definition
this.draw = () => {
const { x, y, r, c } = this;
context.beginPath();
context.arc(x, y, r, 0, 2 * Math.PI);
context.fillStyle = "hsla(" + c + ",100%,50%, 1)";
context.fill();
}
this.bounce = () => {
const { x, y, angle } = this;
if (x > width || x < 0) {
this.turn(180 - 2 * angle);
}
if (y > height || y < 0) {
this.turn(360 - 2 * angle);
}
}
this.turn = (angle, random = false) => {
this.changle = random ? randn(angle) : angle;
this.angle += this.changle;
}
this.forward = d => {
this.d = d;
this.x += this.d * Math.cos(this.angle * Math.PI / 180);
this.y += this.d * Math.sin(this.angle * Math.PI / 180);
}
this.collisionTestArray = a => a
.filter(circle => circle != this)
.forEach(circle => this.collision(circle));
this.collision = circle => {
var differencex = Math.abs(this.x - circle.x);
var differencey = Math.abs(this.y - circle.y);
var hdif = Math.sqrt(differencex ** 2 + differencey ** 2);
if (hdif < this.r + circle.r) {
if (differencex < differencey) {
this.turn(180 - 2 * this.angle);
circle.turn(180 - 2 * circle.angle);
} else {
this.turn(360 - 2 * this.angle);
circle.turn(360 - 2 * circle.angle);
}
this.turn(180);
circle.turn(180);
}
}
// These 2 functions I added to check if the circle was clicked
this.distanceFrom = (x, y) => Math.sqrt((this.x - x) ** 2 + (this.y - y) ** 2);
this.isWithin = (x, y) => this.r > this.distanceFrom(x, y);
}
#canvas {
border: 5px solid orange;
}
#container {
margin: auto;
width: 75%;
text-align: center;
}
<div id="container">
<h1>Click the Blue Circles Only</h1>
<canvas id="canvas" width="1000" height="600"></canvas>
<p>
Points: <span id="points">0</span>
</p>
</div>
using OOP is better in this situation and will save you a lot of time
I have written the OOP version of your game, I wrote it in harry so you may find some bugs but it is good as a starting point
const canvas = document.querySelector("canvas")
const ctx = canvas.getContext("2d")
let h = canvas.height = 600
let w = canvas.width = 800
const numberOfCircles = 20
let circles = []
// running gameover
let gameStatus = "running"
let score = 0
canvas.addEventListener("click", (e) => {
if(gameStatus === "gameOver") {
document.location.reload()
return;
}
const mouse = {x: e.offsetX, y: e.offsetY}
for(let circle of circles) {
if(distance(mouse, circle) <= circle.radius) {
if(circle.color == "blue") {
gameStatus = "running"
score += 1
} else {
gameStatus = "gameOver"
}
}
}
})
class Circle {
constructor(x, y, color, angle) {
this.x = x
this.y = y
this.color = color
this.radius = 15
this.angle = angle
this.speed = 3
}
draw(ctx) {
ctx.beginPath();
ctx.fillStyle = this.color;
ctx.arc(this.x, this.y, this.radius, 0, Math.PI * 2);
ctx.fill();
}
move(circles) {
this.check(circles)
this.x += Math.cos(this.angle) * this.speed
this.y += Math.sin(this.angle) * this.speed
}
check(circles) {
if(this.x + this.radius > w || this.x - this.radius < 0) this.angle += Math.PI
if(this.y + this.radius > h || this.y - this.radius < 0) this.angle += Math.PI
for(let circle of circles) {
if(circle === this) continue
if(distance(this, circle) <= this.radius + circle.radius) {
// invert angles or any other effect
// there are much better soultion for resolving colliusions
circle.angle += Math.PI / 2
this.angle += Math.PI / 2
}
}
}
}
}
setUp()
gameLoop()
function gameLoop() {
ctx.clearRect(0,0,w,h)
if(gameStatus === "gameOver") {
ctx.font = "30px Comic"
ctx.fillText("Game Over", w/2 - 150, h/2 - 100)
ctx.fillText("you have scored : " + score, w/2 - 150, h/2)
return;
}
ctx.font = "30px Comic"
ctx.fillText("score : " + score, 20, 30)
for (let i = 0; i < circles.length; i++) {
const cirlce = circles[i]
cirlce.draw(ctx)
cirlce.move(circles)
}
requestAnimationFrame(gameLoop)
}
function random(to, from = 0) {
return Math.floor(Math.random() * (to - from) + from)
}
function setUp() {
gameStatus = "running"
score = 0
circles = []
for (var i = 0; i < numberOfCircles; i++) {
const randomAngle = random(360) * Math.PI / 180
circles.push(new Circle(random(w, 20), random(h, 20), randomColor(), randomAngle))
}
}
function randomColor() {
const factor = random(10)
if(factor < 3) return "blue"
return `rgb(${random(255)}, ${random(255)}, ${random(100)})`
}
function distance(obj1, obj2) {
const xDiff = obj1.x - obj2.x
const yDiff = obj1.y - obj2.y
return Math.sqrt(Math.pow(xDiff, 2) + Math.pow(yDiff, 2))
}
Related
N-Body gravity simulation seems to be working fine at first glance, and the same is true for body collisions, but once gravitationally attracted objects start to collide, they start to spiral around each other frantically and the collection of them as a whole have very erratic motion... The code (html-javascript) will be included below, and to reproduce what I'm talking about, you can create a new body by clicking in a random location on the screen.
The math for gravitational attraction is done in the Body.prototype.gravityCalc() method of the Body object type (line 261). The math for the collision resolution is found in the dynamic collision section of the bodyHandle() function (line 337).
//////////////////////////////////////////////////////////////////////////////////////////////////////////
// event handling
document.addEventListener('keydown', keyDown);
document.addEventListener('mousedown', mouseDown)
document.addEventListener('mouseup', mouseUp)
document.addEventListener('mousemove', mouseMove);
document.addEventListener('touchstart', touchStart);
document.addEventListener('touchmove', touchMove);
document.addEventListener('touchend', touchEnd);
window.addEventListener('resize', resize);
window.onload = function() {reset()}
mouseDown = false;
nothingGrabbed = true;
mouseX = 0;
mouseY = 0;
function keyDown(data) {
if(data.key == "r") {
clearInterval(loop);
reset();
}
else if(data.key == 'g') {
gravityOn = !gravityOn;
}
else if(data.key == 'Delete') {
for(i = 0; i < bodies.length ; i++) {
if(((mouseX - bodies[i].x)**2 + (mouseY - bodies[i].y)**2) <= bodies[i].radius**2) {
bodies.splice(i, 1);
}
}
}
else if(data.key == 'c') {
gravity_c *= -1;
}
else if(data.key == 'f') {
falling = !falling;
}
else if(data.key == 'a') {
acceleration *= -1;
}
}
function mouseDown(data) {
mouseDown = true;
nothingGrabbed = true;
mouseX = data.clientX;
mouseY = canvas.height - data.clientY;
}
function mouseUp(data) {
mouseDown = false;
nothingGrabbed = true;
for(i = 0; i < bodies.length; i++) {
bodies[i].grabbed = false
}
}
function mouseMove(data) {
mouseX = data.clientX;
mouseY = canvas.height - data.clientY;
}
function touchStart(data) {
mouseDown = true;
nothingGrabbed = true;
mouseX = data.touches[0].clientX;
mouseY = canvas.height - data.touches[0].clientY;
}
function touchMove(data) {
mouseX = data.touches[0].clientX;
mouseY = canvas.height - data.touches[0].clientY;
}
function touchEnd(data) {
mouseDown = false;
nothingGrabbed = true;
for(i=0;i<bodies.length;i++) {
bodies[i].grabbed = false;
}
}
function resize(data) {
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
}
//////////////////////////////////////////////////////////////////////////////////////////////////////////
// Initialize Variables
function reset() {
canvas = document.getElementById("canvas");
ctx = canvas.getContext('2d');
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
canvas.color = 'rgb(70, 70, 70)';
scale = Math.min(canvas.width, canvas.height);
fps = 120;
running = true;
loop = setInterval(main, 1000/fps);
gravityOn = true // if true, objects are gravitationally attracted to each other
gravity_c = 334000 // universe's gravitational constant
boundaryCollision = true // if true, objects collide with edges of canvas
wallDampen = 0.7 // number to multiply by when an objects hit a wall
bodyCollision = true // if true, bodies will collide with each other
bodyDampen = 0.4 // number to multiply when two objects collide
falling = false // if true, objects will fall to the bottom of the screen
acceleration = 400
bodies = [] // a list of each Body object
collidingPairs = [] // a list of pairs of colliding bodies
/*
var bounds = 200;
for(i = 0; i<70; i++) { // randomly place bodies
Body.create({
x: Math.floor(Math.random()*canvas.width),
y: Math.floor(Math.random()*canvas.height),
a: Math.random()*Math.PI*2,
xV: Math.floor(Math.random() * (bounds - -bounds)) + -bounds,
yV: Math.floor(Math.random() * (bounds - -bounds)) + -bounds,
mass: Math.ceil(Math.random()*23)
})
} */
/*
Body.create({
x: canvas.width/2 - 50,
xV: 10,
yV: 0,
aV: 3,
y: canvas.height/2 + 0,
mass: 10
});
Body.create({
x: canvas.width/2 + 50,
xV: 0,
aV: 0,
y: canvas.height/2,
mass: 10
});
*/
Body.create({
x: canvas.width/2,
y: canvas.height/2,
mass: 24,
xV: -10.83
});
Body.create({
x: canvas.width/2,
y: canvas.height/2 + 150,
mass: 1,
xV: 260,
color: 'teal'
});
}
//////////////////////////////////////////////////////////////////////////////////////////////////////////
// Body Type Object
function Body(params) {
this.x = params.x || canvas.width/2;
this.y = params.y || canvas.height/2;
this.a = params.a || 0;
this.xV = params.xV || 0;
this.yV = params.yV || 0;
this.aV = params.aV || 0;
this.xA = params.xA || 0;
this.yA = params.yA || 0;
this.aA = params.aA || 0;
this.grabbed = false;
this.edgeBlock = params.edgeBlock || boundaryCollision;
this.gravity = params.gravityOn || gravityOn;
this.mass = params.mass || 6;
this.density = params.density || 0.008;
this.radius = params.radius || (this.mass/(Math.PI*this.density))**0.5;
this.color = params.color || 'crimson';
this.lineWidth = params.lineWidth || 2;
}
Body.create = function(params) {
bodies.push(new Body(params));
}
Body.prototype.move = function() {
this.xV += this.xA/fps;
this.yV += this.yA/fps;
this.aV += this.aA/fps;
this.x += this.xV/fps;
this.y += this.yV/fps;
this.a += this.aV/fps;
if(this.edgeBlock) {
if(this.x + this.radius > canvas.width) {
this.x = canvas.width - this.radius;
this.xV *= -wallDampen
}
else if(this.x - this.radius < 0) {
this.x = this.radius;
this.xV *= -wallDampen;
}
if(this.y + this.radius > canvas.height) {
this.y = canvas.height - this.radius;
this.yV *= -wallDampen;
}
else if(this.y - this.radius < 0) {
this.y = this.radius;
this.yV *= -wallDampen;
}
}
if(this.grabbed) {
this.xA = 0;
this.yA = 0;
this.xV = 0;
this.yV = 0;
this.x = mouseX;
this.y = mouseY;
}
}
Body.prototype.draw = function() {
ctx.beginPath();
ctx.strokeStyle = 'black';
ctx.lineWidth = this.lineWidth;
ctx.fillStyle = this.color;
ctx.arc(this.x, canvas.height - this.y, this.radius, 0, Math.PI*2, true);
ctx.fill();
ctx.stroke();
ctx.closePath()
ctx.beginPath();
ctx.strokeStyle = 'black';
ctx.lineWidth = this.linewidth;
ctx.moveTo(this.x, canvas.height - this.y);
ctx.lineTo(this.x + this.radius*Math.cos(this.a), canvas.height - (this.y + this.radius*Math.sin(this.a)))
ctx.stroke();
ctx.closePath();
}
// calculates gravitational attraction to 'otherObject'
Body.prototype.gravityCalc = function(otherObject) {
var x1 = this.x;
var y1 = this.y;
var x2 = otherObject.x;
var y2 = otherObject.y;
var distSquare = ((x2-x1)**2 + (y2-y1)**2);
var val = (gravity_c*otherObject.mass)/((distSquare)**(3/2));
var xA = val * (x2 - x1);
var yA = val * (y2 - y1);
return [xA, yA]
}
//////////////////////////////////////////////////////////////////////////////////////////////////////////
// Physics Code
function bodyHandle() {
for(i = 0; i < bodies.length; i++) {
if(mouseDown && nothingGrabbed) {
if(Math.abs((mouseX - bodies[i].x)**2 + (mouseY - bodies[i].y)**2) <= bodies[i].radius**2) {
bodies[i].grabbed = true;
nothingGrabbed = false;
}
}
bodies[i].draw()
if(running) {
if(falling) {
bodies[i].yV -= acceleration/fps;
}
bodies[i].move();
}
bodies[i].xA = 0;
bodies[i].yA = 0;
collidingPairs = []
if(gravityOn || bodyCollision) {
for(b = 0; b < bodies.length; b++) {
if(i != b) {
if(bodyCollision) {
var x1 = bodies[i].x;
var y1 = bodies[i].y;
var x2 = bodies[b].x;
var y2 = bodies[b].y;
var rSum = bodies[i].radius + bodies[b].radius;
var dist = { // vector
i: x2 - x1,
j: y2 - y1,
mag: ((x2-x1)**2 + (y2-y1)**2)**0.5,
norm: {
i: (x2-x1)/(((x2-x1)**2 + (y2-y1)**2)**0.5),
j: (y2-y1)/(((x2-x1)**2 + (y2-y1)**2)**0.5)
}
}
if(dist.mag <= rSum) { // static collision
var overlap = rSum - dist.mag;
bodies[i].x -= overlap/2 * dist.norm.i;
bodies[i].y -= overlap/2 * dist.norm.j;
bodies[b].x += overlap/2 * dist.norm.i;
bodies[b].y += overlap/2 * dist.norm.j;
collidingPairs.push([bodies[i], bodies[b]]);
}
}
if(gravityOn) {
if(bodies[i].gravity) {
var accel = bodies[i].gravityCalc(bodies[b]);
bodies[i].xA += accel[0];
bodies[i].yA += accel[1];
}
}
}
}
}
for(c = 0; c < collidingPairs.length; c++) { // dynamic collision
var x1 = collidingPairs[c][0].x;
var y1 = collidingPairs[c][0].y;
var r1 = collidingPairs[c][0].radius;
var x2 = collidingPairs[c][1].x;
var y2 = collidingPairs[c][1].y;
var r2 = collidingPairs[c][1].radius;
var dist = { // vector from b1 to b2
i: x2 - x1,
j: y2 - y1,
mag: ((x2-x1)**2 + (y2-y1)**2)**0.5,
norm: {
i: (x2-x1)/(((x2-x1)**2 + (y2-y1)**2)**0.5),
j: (y2-y1)/(((x2-x1)**2 + (y2-y1)**2)**0.5)
}
}
var m1 = collidingPairs[c][0].mass;
var m2 = collidingPairs[c][1].mass;
var norm = { // vector normal along 'wall' of collision
i: -dist.j/(((dist.i)**2 + (-dist.j)**2)**0.5),
j: dist.i/(((dist.i)**2 + (-dist.j)**2)**0.5)
}
var perp = { // vector normal pointing from b1 to b2
i: dist.norm.i,
j: dist.norm.j
}
var vel1 = { // vector of b1 velocity
i: collidingPairs[c][0].xV,
j: collidingPairs[c][0].yV,
dot: function(vect) {
return collidingPairs[c][0].xV * vect.i + collidingPairs[c][0].yV * vect.j
}
}
var vel2 = { // vector of b2 velocity
i: collidingPairs[c][1].xV,
j: collidingPairs[c][1].yV,
dot: function(vect) {
return collidingPairs[c][1].xV * vect.i + collidingPairs[c][1].yV * vect.j
}
}
// new velocities along perp^ of b1 and b2
var nV1Perp = (vel1.dot(perp))*(m1-m2)/(m1+m2) + (vel2.dot(perp))*(2*m2)/(m1+m2);
var nV2Perp = (vel1.dot(perp))*(2*m1)/(m1+m2) + (vel2.dot(perp))*(m2-m1)/(m1+m2);
/* testing rotation after collision
// velocities of the points of collision on b1 and b2
var pVel1M = vel1.dot(norm) + collidingPairs[c][0].aV*r1;
var pVel2M = vel2.dot(norm) + collidingPairs[c][1].aV*r2;
// moment of inertia for b1 and b2
var I1 = 1/2 * m1 * r1**2;
var I2 = 1/2 * m2 * r2**2;
// new velocities of the points of collisions on b1 and b2
var newpVel1M = ((I1-I2)/(I1+I2))*pVel1M + ((2*I2)/(I1+I2))*pVel2M;
var newpVel2M = ((2*I1)/(I1+I2))*pVel1M + ((I2-I1)/(I1+I2))*pVel2M;
var vectToCol1 = { // vector from x1,y1 to point of collision on b1
i: r1*perp.i,
j: r1*perp.j
};
var vectToCol2 = { // vector from x2,y2 to point of collision on b2
i: r2*-perp.i,
j: r2*-perp.j
};
// sign of cross product of pVelM and vectToCol
var vCrossR1 = (pVel1M*norm.i)*(vectToCol1.j) - (pVel1M*norm.j)*(vectToCol1.i);
vCrossR1 = vCrossR1/Math.abs(vCrossR1);
var vCrossR2 = (pVel2M*norm.i)*(vectToCol2.j) - (pVel2M*norm.j)*(vectToCol2.i);
vCrossR2 = vCrossR2/Math.abs(vCrossR2);
collidingPairs[c][0].aV = vCrossR1 * (newpVel1M)/r1;
collidingPairs[c][1].aV = vCrossR2 * (newpVel2M)/r2;
/* draw collision point velocity vectors [debugging]
ctx.beginPath();
ctx.strokeStyle = 'black';
ctx.moveTo(x1 + vectToCol1.i, canvas.height - (y1 + vectToCol1.j));
ctx.lineTo((x1+vectToCol1.i) + pVel1M*norm.i, (canvas.height- (y1+vectToCol1.j + pVel1M*norm.j)));
ctx.stroke();
ctx.closePath();
ctx.beginPath();
ctx.strokeStyle = 'white';
ctx.moveTo(x2 + vectToCol2.i, canvas.height - (y2 + vectToCol2.j));
ctx.lineTo((x2+vectToCol2.i) + pVel2M*norm.i, (canvas.height- (y2+vectToCol2.j + pVel2M*norm.j)));
ctx.stroke();
ctx.closePath();
console.log(pVel1M, pVel2M);
clearInterval(loop);
*/
collidingPairs[c][0].xV = vel1.dot(norm)*norm.i + nV1Perp*perp.i * bodyDampen;
collidingPairs[c][0].yV = vel1.dot(norm)*norm.j + nV1Perp*perp.j * bodyDampen;
collidingPairs[c][1].xV = vel2.dot(norm)*norm.i + nV2Perp*perp.i * bodyDampen;
collidingPairs[c][1].yV = vel2.dot(norm)*norm.j + nV2Perp*perp.j * bodyDampen;
}
}
}
//////////////////////////////////////////////////////////////////////////////////////////////////////////
// Main Loop
function main() {
// blank out canvas
ctx.fillStyle = canvas.color;
ctx.fillRect(0, 0, canvas.width, canvas.height);
bodyHandle();
if(nothingGrabbed && mouseDown) {
bodies.push(new Body({x: mouseX,
y: mouseY,
mass: 90}));
bodies[bodies.length-1].move();
bodies[bodies.length-1].draw();
}
}
<html>
<meta name='viewport' content='width=device-width,height=device-height'>
<body>
<canvas id="canvas" width='300px' height='300px'></canvas>
<style>
body {
padding: 0;
margin: 0;
}
canvas {
padding: 0;
margin: 0;
}
</style>
</html>
I cannot tell you much about the code. Personally it seems to me that the animations could be correct.
If you want to test your code you could try to test if laws of conservation of energy and momentum are respected. You could, for example, sum the momentum of every object (mass times velocity) and see if the number are maintained constant when there are no forces from the outside (collisions with the wall). To do this I would suggest to make the free space available larger. Another quantity is the total energy (kinetic plus potential) which is a bit harder, but still easy to compute (to compute tot. pot. energy you have to sum over all pairs).
I'm working on a certain layout where I need to draw a hexagon which needs to be clickable. I'm using the Path2D construct and isPointInPath function. I'm constructing an animation where a number of hexagons is created and then each moved to a certain position. After the movement is done, I am attaching onclick event handlers to certain hexagons. However there is weird behaviour.
Some initialized variables
const COLOR_DARK = "#73b6c6";
const COLOR_LIGHT = "#c3dadd";
const COLOR_PRIMARY = "#39a4c9";
const TYPE_PRIMARY = 'primary';
let hexagons = [];
Below is the function which draws the hexagons.
function drawHex(ctx, x, y, hexProps, stroke, color) {
let myPath = new Path2D();
myPath.moveTo(x + hexProps.width*0.5, y);
myPath.lineTo(x, y + hexProps.height*hexProps.facShort);
myPath.lineTo(x, y + hexProps.height*hexProps.facLong);
myPath.lineTo(x + hexProps.width*0.5, y + hexProps.height);
myPath.lineTo(x + hexProps.width, y + hexProps.height*hexProps.facLong);
myPath.lineTo(x + hexProps.width, y + hexProps.height*hexProps.facShort);
myPath.lineTo(x + hexProps.width*0.5, y);
myPath.closePath();
if (stroke){
ctx.strokeStyle = color;
ctx.stroke(myPath);
} else {
ctx.fillStyle = color;
ctx.fill(myPath);
}
return myPath;
}
This function populates the hexagon array
function populateLeftHex(canvasWidth, canvasHeight, hexProps) {
const startX = canvasWidth / 2;
const startY = canvasHeight / 2;
const baseLeft = canvasWidth * 0.05;
for(let i = 0; i < 5; i++){
let hexNumber = (i % 4 == 0)? 2: 1;
for(let j = 0; j < hexNumber; j++){
hexagons.push({
startX: startX,
startY: startY,
endX: baseLeft + (2 * j) + ((i % 2 == 0)? (hexProps.width * j) : (hexProps.width/2)),
endY: ((i + 1) * hexProps.height) - ((i) * hexProps.height * hexProps.facShort) + (i* 2),
stroke: true,
color: ( i % 2 == 0 && j % 2 == 0)? COLOR_DARK : COLOR_LIGHT,
type: TYPE_PRIMARY
});
}
}
}
And here is where Im calling the isPointInPath function.
window.onload = function (){
const c = document.getElementById('canvas');
const canvasWidth = c.width = window.innerWidth,
canvasHeight = c.height = window.innerHeight,
ctx = c.getContext('2d');
window.requestAnimFrame = (function (callback) {
return window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || window.oRequestAnimationFrame || window.msRequestAnimationFrame || function (callback) {
window.setTimeout(callback, 1000 / 60);
};
})();
console.log(canvasWidth);
let hexProps = {
width: canvasWidth * 0.075,
get height () {
return this.width/Math.sqrt(3) + (1.5)*(this.width/Math.sqrt(2)/2);
} ,
facShort: 0.225,
get facLong () {
return 1 - this.facShort;
}
};
populateLeftHex(canvasWidth, canvasHeight, hexProps);
let pct = 0;
const fps = 200;
animate();
function animate () {
setTimeout(function () {
// increment pct towards 100%
pct += .03;
// if we're not done, request another animation frame
if (pct < 1.00) {
requestAnimFrame(animate);
} else { //if pct is no longer less than 1.00, then the movement animation is over.
hexagons.forEach(function (hex) {
if(hex.type === TYPE_PRIMARY) {
console.info(hex.path);
c.onclick = function(e) {
let x = e.clientX - c.offsetLeft,
y = e.clientY - c.offsetTop;
console.info(ctx.isPointInPath(hex.path, (e.clientX - c.offsetLeft), (e.clientY - c.offsetTop) ));
};
}
})
}
ctx.clearRect(0, 0, c.width, c.height);
// draw all hexagons
for ( let i = 0; i < hexagons.length; i++) {
// get reference to next shape
let hex = hexagons[i];
// note: dx/dy are fixed values
// they could be put in the shape object for efficiency
let dx = hex.endX - hex.startX;
let dy = hex.endY - hex.startY;
let nextX = hex.startX + dx * pct;
let nextY = hex.startY + dy * pct;
hex = hexagons[i];
ctx.fillStyle = hex.color;
hex.path = drawHex(ctx, nextX, nextY, hexProps, hex.stroke, hex.color);
}
}, 1000 / fps);
}
Can you help me figure out what I'm doing wrong? Maybe I misunderstood how Path2D works? Thanks in advance.
Had to do a bit of work to build a test page as your example is incomplete, but this is working for me - though my hexagon is concave...
var myCanvas = document.getElementById("myCanvas");
var ctx = myCanvas.getContext("2d");
var hexProps = {width:100, height:100, facShort:-2, facLong:10};
var hexagons = [];
function drawHex(ctx, x, y, hexProps, stroke, color) {
let myPath = new Path2D();
myPath.moveTo(x + hexProps.width*0.5, y);
myPath.lineTo(x, y + hexProps.height*hexProps.facShort);
myPath.lineTo(x, y + hexProps.height*hexProps.facLong);
myPath.lineTo(x + hexProps.width*0.5, y + hexProps.height);
myPath.lineTo(x + hexProps.width, y + hexProps.height*hexProps.facLong);
myPath.lineTo(x + hexProps.width, y + hexProps.height*hexProps.facShort);
myPath.lineTo(x + hexProps.width*0.5, y);
myPath.closePath();
if (stroke){
ctx.strokeStyle = color;
ctx.stroke(myPath);
} else {
ctx.fillStyle = color;
ctx.fill(myPath);
}
return myPath;
}
hexagons.push({type:0, path:drawHex(ctx,100,100,hexProps,false,"#0f0")});
hexagons.forEach(function (hex) {
if(hex.type === 0) {
console.info(hex.path);
myCanvas.onclick = function(e) {
let x = e.clientX - myCanvas.offsetLeft,
y = e.clientY - myCanvas.offsetTop;
console.info(x,y);
console.info(ctx.isPointInPath(hex.path, (e.clientX -
myCanvas.offsetLeft), (e.clientY - myCanvas.offsetTop) ));
};
}
})
<canvas width=500 height=500 id=myCanvas style='border:1px solid red'></canvas>
Test clicks give true and false where expected:
test.htm:48 165 168
test.htm:49 true
test.htm:48 151 336
test.htm:49 false
test.htm:48 124 314
test.htm:49 true
test.htm:48 87 311
test.htm:49 false
I'm trying to create a hyperdrive effect, like from Star Wars, where the stars have a motion trail. I've gotten as far as creating the motion trail on a single circle, it still looks like the trail is going down in the y direction and not forwards or positive in the z direction.
Also, how could I do this with (many) randomly placed circles as if they were stars?
My code is on jsfiddle (https://jsfiddle.net/5m7x5zxu/) and below:
var canvas = document.querySelector("canvas");
var context = canvas.getContext("2d");
var xPos = 180;
var yPos = 100;
var motionTrailLength = 16;
var positions = [];
function storeLastPosition(xPos, yPos) {
// push an item
positions.push({
x: xPos,
y: yPos
});
//get rid of first item
if (positions.length > motionTrailLength) {
positions.pop();
}
}
function update() {
context.clearRect(0, 0, canvas.width, canvas.height);
for (var i = positions.length-1; i > 0; i--) {
var ratio = (i - 1) / positions.length;
drawCircle(positions[i].x, positions[i].y, ratio);
}
drawCircle(xPos, yPos, "source");
var k=2;
storeLastPosition(xPos, yPos);
// update position
if (yPos > 125) {
positions.pop();
}
else{
yPos += k*1.1;
}
requestAnimationFrame(update);
}
update();
function drawCircle(x, y, r) {
if (r == "source") {
r = 1;
} else {
r*=1.1;
}
context.beginPath();
context.arc(x, y, 3, 0, 2 * Math.PI, true);
context.fillStyle = "rgba(255, 255, 255, " + parseFloat(1-r) + ")";
context.fill();
}
Canvas feedback and particles.
This type of FX can be done many ways.
You could just use a particle systems and draw stars (as lines) moving away from a central point, as the speed increase you increase the line length. When at low speed the line becomes a circle if you set ctx.lineWidth > 1 and ctx.lineCap = "round"
To add to the FX you can use render feedback as I think you have done by rendering the canvas over its self. If you render it slightly larger you get a zoom FX. If you use ctx.globalCompositeOperation = "lighter" you can increase the stars intensity as you speed up to make up for the overall loss of brightness as stars move faster.
Example
I got carried away so you will have to sift through the code to find what you need.
The particle system uses the Point object and a special array called bubbleArray to stop GC hits from janking the animation.
You can use just an ordinary array if you want. The particles are independent of the bubble array. When they have moved outside the screen they are move to a pool and used again when a new particle is needed. The update function moves them and the draw Function draws them I guess LOL
The function loop is the main loop and adds and draws particles (I have set the particle count to 400 but should handle many more)
The hyper drive is operated via the mouse button. Press for on, let go for off. (It will distort the text if it's being displayed)
The canvas feedback is set via that hyperSpeed variable, the math is a little complex. The sCurce function just limits the value to 0,1 in this case to stop alpha from going over or under 1,0. The hyperZero is just the sCurve return for 1 which is the hyper drives slowest speed.
I have pushed the feedback very close to the limit. In the first few lines of the loop function you can set the top speed if(mouse.button){ if(hyperSpeed < 1.75){ Over this value 1.75 and you will start to get bad FX, at about 2 the whole screen will just go white (I think that was where)
Just play with it and if you have questions ask in the comments.
const ctx = canvas.getContext("2d");
// very simple mouse
const mouse = {x : 0, y : 0, button : false}
function mouseEvents(e){
mouse.x = e.pageX;
mouse.y = e.pageY;
mouse.button = e.type === "mousedown" ? true : e.type === "mouseup" ? false : mouse.button;
}
["down","up","move"].forEach(name => document.addEventListener("mouse"+name,mouseEvents));
// High performance array pool using buubleArray to separate pool objects and active object.
// This is designed to eliminate GC hits involved with particle systems and
// objects that have short lifetimes but used often.
// Warning this code is not well tested.
const bubbleArray = () => {
const items = [];
var count = 0;
return {
clear(){ // warning this dereferences all locally held references and can incur Big GC hit. Use it wisely.
this.items.length = 0;
count = 0;
},
update() {
var head, tail;
head = tail = 0;
while(head < count){
if(items[head].update() === false) {head += 1 }
else{
if(tail < head){
const temp = items[head];
items[head] = items[tail];
items[tail] = temp;
}
head += 1;
tail += 1;
}
}
return count = tail;
},
createCallFunction(name, earlyExit = false){
name = name.split(" ")[0];
const keys = Object.keys(this);
if(Object.keys(this).indexOf(name) > -1){ throw new Error(`Can not create function name '${name}' as it already exists.`) }
if(!/\W/g.test(name)){
let func;
if(earlyExit){
func = `var items = this.items; var count = this.getCount(); var i = 0;\nwhile(i < count){ if (items[i++].${name}() === true) { break } }`;
}else{
func = `var items = this.items; var count = this.getCount(); var i = 0;\nwhile(i < count){ items[i++].${name}() }`;
}
!this.items && (this.items = items);
this[name] = new Function(func);
}else{ throw new Error(`Function name '${name}' contains illegal characters. Use alpha numeric characters.`) }
},
callEach(name){var i = 0; while(i < count){ if (items[i++][name]() === true) { break } } },
each(cb) { var i = 0; while(i < count){ if (cb(items[i], i++) === true) { break } } },
next() { if (count < items.length) { return items[count ++] } },
add(item) {
if(count === items.length){
items.push(item);
count ++;
}else{
items.push(items[count]);
items[count++] = item;
}
return item;
},
getCount() { return count },
}
}
// Helpers rand float, randI random Int
// doFor iterator
// sCurve curve input -Infinity to Infinity out -1 to 1
// randHSLA creates random colour
// CImage, CImageCtx create image and image with context attached
const randI = (min, max = min + (min = 0)) => (Math.random() * (max - min) + min) | 0;
const rand = (min = 1, max = min + (min = 0)) => Math.random() * (max - min) + min;
const doFor = (count, cb) => { var i = 0; while (i < count && cb(i++) !== true); }; // the ; after while loop is important don't remove
const sCurve = (v,p) => (2 / (1 + Math.pow(p,-v))) -1;
const randHSLA = (h, h1, s = 100, s1 = 100, l = 50, l1 = 50, a = 1, a1 = 1) => { return `hsla(${randI(h,h1) % 360},${randI(s,s1)}%,${randI(l,l1)}%,${rand(a,a1)})` }
const CImage = (w = 128, h = w) => (c = document.createElement("canvas"),c.width = w,c.height = h, c);
const CImageCtx = (w = 128, h = w) => (c = CImage(w,h), c.ctx = c.getContext("2d"), c);
// create image to hold text
var textImage = CImageCtx(1024, 1024);
var c = textImage.ctx;
c.fillStyle = "#FF0";
c.font = "64px arial black";
c.textAlign = "center";
c.textBaseline = "middle";
const text = "HYPER,SPEED FX,VII,,Battle of Jank,,Hold the mouse,button to increase,speed.".split(",");
text.forEach((line,i) => { c.fillText(line,512,i * 68 + 68) });
const maxLines = text.length * 68 + 68;
function starWarIntro(image,x1,y1,x2,y2,pos){
var iw = image.width;
var ih = image.height;
var hh = (x2 - x1) / (y2 - y1); // Slope of left edge
var w2 = iw / 2; // half width
var z1 = w2 - x1; // Distance (z) to first line
var z2 = (z1 / (w2 - x2)) * z1 - z1; // distance (z) between first and last line
var sk,t3,t3a,z3a,lines, z3, dd = 0, a = 0, as = 2 / (y2 - y1);
for (var y = y1; y < y2 && dd < maxLines; y++) { // for each line
t3 = ((y - y1) * hh) + x1; // get scan line top left edge
t3a = (((y+1) - y1) * hh) + x1; // get scan line bottom left edge
z3 = (z1 / (w2 - t3)) * z1; // get Z distance to top of this line
z3a = (z1 / (w2 - t3a)) * z1; // get Z distance to bottom of this line
dd = ((z3 - z1) / z2) * ih; // get y bitmap coord
a += as;
ctx.globalAlpha = a < 1 ? a : 1;
dd += pos; // kludge for this answer to make text move
// does not move text correctly
lines = ((z3a - z1) / z2) * ih-dd; // get number of lines to copy
ctx.drawImage(image, 0, dd , iw, lines, t3, y, w - t3 * 2, 1.5);
}
}
// canvas settings
var w = canvas.width;
var h = canvas.height;
var cw = w / 2; // center
var ch = h / 2;
// diagonal distance used to set point alpha (see point update)
var diag = Math.sqrt(w * w + h * h);
// If window size is changed this is called to resize the canvas
// It is not called via the resize event as that can fire to often and
// debounce makes it feel sluggish so is called from main loop.
function resizeCanvas(){
points.clear();
canvas.width = innerWidth;
canvas.height = innerHeight;
w = canvas.width;
h = canvas.height;
cw = w / 2; // center
ch = h / 2;
diag = Math.sqrt(w * w + h * h);
}
// create array of points
const points = bubbleArray();
// create optimised draw function itterator
points.createCallFunction("draw",false);
// spawns a new star
function spawnPoint(pos){
var p = points.next();
p = points.add(new Point())
if (p === undefined) { p = points.add(new Point()) }
p.reset(pos);
}
// point object represents a single star
function Point(pos){ // this function is duplicated as reset
if(pos){
this.x = pos.x;
this.y = pos.y;
this.dead = false;
}else{
this.x = 0;
this.y = 0;
this.dead = true;
}
this.alpha = 0;
var x = this.x - cw;
var y = this.y - ch;
this.dir = Math.atan2(y,x);
this.distStart = Math.sqrt(x * x + y * y);
this.speed = rand(0.01,1);
this.col = randHSLA(220,280,100,100,50,100);
this.dx = Math.cos(this.dir) * this.speed;
this.dy = Math.sin(this.dir) * this.speed;
}
Point.prototype = {
reset : Point, // resets the point
update(){ // moves point and returns false when outside
this.speed *= hyperSpeed; // increase speed the more it has moved
this.x += Math.cos(this.dir) * this.speed;
this.y += Math.sin(this.dir) * this.speed;
var x = this.x - cw;
var y = this.y - ch;
this.alpha = (Math.sqrt(x * x + y * y) - this.distStart) / (diag * 0.5 - this.distStart);
if(this.alpha > 1 || this.x < 0 || this.y < 0 || this.x > w || this.h > h){
this.dead = true;
}
return !this.dead;
},
draw(){ // draws the point
ctx.strokeStyle = this.col;
ctx.globalAlpha = 0.25 + this.alpha *0.75;
ctx.beginPath();
ctx.lineTo(this.x - this.dx * this.speed, this.y - this.dy * this.speed);
ctx.lineTo(this.x, this.y);
ctx.stroke();
}
}
const maxStarCount = 400;
const p = {x : 0, y : 0};
var hyperSpeed = 1.001;
const alphaZero = sCurve(1,2);
var startTime;
function loop(time){
if(startTime === undefined){
startTime = time;
}
if(w !== innerWidth || h !== innerHeight){
resizeCanvas();
}
// if mouse down then go to hyper speed
if(mouse.button){
if(hyperSpeed < 1.75){
hyperSpeed += 0.01;
}
}else{
if(hyperSpeed > 1.01){
hyperSpeed -= 0.01;
}else if(hyperSpeed > 1.001){
hyperSpeed -= 0.001;
}
}
var hs = sCurve(hyperSpeed,2);
ctx.globalAlpha = 1;
ctx.setTransform(1,0,0,1,0,0); // reset transform
//==============================================================
// UPDATE the line below could be the problem. Remove it and try
// what is under that
//==============================================================
//ctx.fillStyle = `rgba(0,0,0,${1-(hs-alphaZero)*2})`;
// next two lines are the replacement
ctx.fillStyle = "Black";
ctx.globalAlpha = 1-(hs-alphaZero) * 2;
//==============================================================
ctx.fillRect(0,0,w,h);
// the amount to expand canvas feedback
var sx = (hyperSpeed-1) * cw * 0.1;
var sy = (hyperSpeed-1) * ch * 0.1;
// increase alpha as speed increases
ctx.globalAlpha = (hs-alphaZero)*2;
ctx.globalCompositeOperation = "lighter";
// draws feedback twice
ctx.drawImage(canvas,-sx, -sy, w + sx*2 , h + sy*2)
ctx.drawImage(canvas,-sx/2, -sy/2, w + sx , h + sy)
ctx.globalCompositeOperation = "source-over";
// add stars if count < maxStarCount
if(points.getCount() < maxStarCount){
var cent = (hyperSpeed - 1) *0.5; // pulls stars to center as speed increases
doFor(10,()=>{
p.x = rand(cw * cent ,w - cw * cent); // random screen position
p.y = rand(ch * cent,h - ch * cent);
spawnPoint(p)
})
}
// as speed increases make lines thicker
ctx.lineWidth = 2 + hs*2;
ctx.lineCap = "round";
points.update(); // update points
points.draw(); // draw points
ctx.globalAlpha = 1;
// scroll the perspective star wars text FX
var scrollTime = (time - startTime) / 5 - 2312;
if(scrollTime < 1024){
starWarIntro(textImage,cw - h * 0.5, h * 0.2, cw - h * 3, h , scrollTime );
}
requestAnimationFrame(loop);
}
requestAnimationFrame(loop);
canvas { position : absolute; top : 0px; left : 0px; }
<canvas id="canvas"></canvas>
Here's another simple example, based mainly on the same idea as Blindman67, concetric lines moving away from center at different velocities (the farther from center, the faster it moves..) also no recycling pool here.
"use strict"
var c = document.createElement("canvas");
document.body.append(c);
var ctx = c.getContext("2d");
var w = window.innerWidth;
var h = window.innerHeight;
var ox = w / 2;
var oy = h / 2;
c.width = w; c.height = h;
const stars = 120;
const speed = 0.5;
const trailLength = 90;
ctx.fillStyle = "#000";
ctx.fillRect(0, 0, w, h);
ctx.fillStyle = "#fff"
ctx.fillRect(ox, oy, 1, 1);
init();
function init() {
var X = [];
var Y = [];
for(var i = 0; i < stars; i++) {
var x = Math.random() * w;
var y = Math.random() * h;
X.push( translateX(x) );
Y.push( translateY(y) );
}
drawTrails(X, Y)
}
function translateX(x) {
return x - ox;
}
function translateY(y) {
return oy - y;
}
function getDistance(x, y) {
return Math.sqrt(x * x + y * y);
}
function getLineEquation(x, y) {
return function(n) {
return y / x * n;
}
}
function drawTrails(X, Y) {
var count = 1;
ctx.fillStyle = "#000";
ctx.fillRect(0, 0, w, h);
function anim() {
for(var i = 0; i < X.length; i++) {
var x = X[i];
var y = Y[i];
drawNextPoint(x, y, count);
}
count+= speed;
if(count < trailLength) {
window.requestAnimationFrame(anim);
}
else {
init();
}
}
anim();
}
function drawNextPoint(x, y, step) {
ctx.fillStyle = "#fff";
var f = getLineEquation(x, y);
var coef = Math.abs(x) / 100;
var dist = getDistance( x, y);
var sp = speed * dist / 100;
for(var i = 0; i < sp; i++) {
var newX = x + Math.sign(x) * (step + i) * coef;
var newY = translateY( f(newX) );
ctx.fillRect(newX + ox, newY, 1, 1);
}
}
body {
overflow: hidden;
}
canvas {
position: absolute;
left: 0;
top: 0;
}
I am trying to create a blackhole simulation, where all the balls that are outside of it go away from it at a given speed and those that fall on it are dragged towards the circle until they reach the center of it, where they would stop and disappear, here is my code:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8" />
<title>blackhole simulation escape velocity</title>
<script>
var canvas, ctx;
var blackhole;
var circle;
var circles = new Array();
var G = 6.67e-11, //gravitational constant
pixel_G = G / 1e-11,
c = 3e8, //speed of light (m/s)
M = 12e31, // masseof the blackhole in kg (60 solar masses)
pixel_M = M / 1e32
Rs = (2 * G * M) / 9e16, //Schwarzchild radius
pixel_Rs = Rs / 1e3, // scaled radius
ccolor = 128;
function update() {
var pos, i, distance, somethingMoved = false;
for (i = 0; i < circles.length; i++) {
pos = circles[i].position;
distance = Math.sqrt(((pos.x - 700) * (pos.x - 700)) + ((pos.y - 400) * (pos.y - 400)));
if (distance > pixel_Rs-5 ) {
var delta = new Vector2D(0, 0);
var forceDirection = Math.atan2(pos.y - 400, pos.x - 700);
var evelocity = Math.sqrt((2 * pixel_G * pixel_M) / (distance * 1e-2));
delta.x += Math.cos(forceDirection) * evelocity;
delta.y += Math.sin(forceDirection) * evelocity;
pos.x += delta.x;
pos.y += delta.y;
somethingMoved = true;
} else {
var delta2 = new Vector2D (0,0);
var forceDirection2 = Math.atan2(pos.y - 400, pos.x - 700);
var g = (pixel_G*pixel_M)/(distance*distance*1e2);
delta2.x += Math.cos(forceDirection2)*g;
delta2.y += Math.sin(forceDirection2)*g;
pos.x -= delta2.x;
pos.y -= delta2.y;
somethingMoved = true;
circles[i].color -= 1;
if (pos.x == 700 && pos.y == 400){
somethingMoved = false;
};
}
}
if (somethingMoved) {
drawEverything();
requestAnimationFrame(update);
};
}
function drawEverything() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
blackhole.draw(ctx);
for (var i = 0; i < circles.length; i++) {
circles[i].draw(ctx);
}
}
function init(event) {
canvas = document.getElementById("space");
ctx = canvas.getContext('2d');
blackhole = new Ball(pixel_Rs, { x: 700,
y: 400 }, 0);
for (var i = 0; i < 200; i++) {
var vec2D = new Vector2D(Math.floor(Math.random() * 1400), Math.floor(Math.random() * 800));
circle = new Ball(5, vec2D, ccolor);
circles.push(circle);
}
drawEverything();
requestAnimationFrame(update);
}
function Ball(radius, position, color) {
this.radius = radius;
this.position = position;
this.color = color;
}
Ball.prototype.draw = function(ctx) {
var c=parseInt(this.color);
ctx.fillStyle = 'rgba(' + c + ',' + c + ',' + c + ',1)';
ctx.beginPath();
ctx.arc(this.position.x, this.position.y, this.radius, 0, 2 * Math.PI);
ctx.closePath();
ctx.fill();
};
function Vector2D(x, y) {
this.x = x;
this.y = y;
}
function onClick (){
canvas = document.getElementById ('space');
ctx = canvas.getContext ('2d')
canvas.addEventListener ("mousedown", init, false)
blackhole = new Ball (5, {x: 700,
y: 400 }, 0);
blackhole.draw (ctx) ;
}
window.onload = onClick;
</script>
<style>
body {
background-color:#021c36 ;
margin: 0px;
}
</style>
</head>
<body>
<canvas id = "space", width = "1400", height = "800">
</canvas>
</body>
</html>
Now as you can see, I created a second variable called delta2, but the problem is that it can't update the position of the circles, which in term makes it impossible to move the circle, can someone tell me what is wrong. Also, how can I make the big black circle after a certain amount of time, i know i probably should create a timer, but i don't know how they work
The gravity is too weak. I put a pseudo gravity to demonstrate.
var canvas, ctx;
var blackhole;
var circle;
var circles = new Array();
var bh = {
w:500,
h:300
};
bh.cx = Math.floor(bh.w/2);
bh.cy = Math.floor(bh.h/2)
var G = 6.67e-11, //gravitational constant
pixel_G = G / 1e-11,
c = 3e8, //speed of light (m/s)
M = 12e31, // masseof the blackhole in kg (60 solar masses)
pixel_M = M / 1e32
Rs = (2 * G * M) / 9e16, //Schwarzchild radius
pixel_Rs = Rs / 1e3, // scaled radius
ccolor = 128;
function update() {
var pos, i, distance, somethingMoved = false;
for (i = 0; i < circles.length; i++) {
pos = circles[i].position;
distance = Math.sqrt(((pos.x - bh.cx) * (pos.x - bh.cx)) + ((pos.y - bh.cy) * (pos.y - bh.cy)));
if (distance > pixel_Rs - 5) {
var delta = new Vector2D(0, 0);
var forceDirection = Math.atan2(pos.y - bh.cy, pos.x - bh.cx);
var evelocity = Math.sqrt((2 * pixel_G * pixel_M) / (distance * 1e-2));
delta.x += Math.cos(forceDirection) * evelocity;
delta.y += Math.sin(forceDirection) * evelocity;
pos.x += delta.x;
pos.y += delta.y;
somethingMoved = true;
} else {
var delta2 = new Vector2D(0, 0);
var forceDirection2 = Math.atan2(pos.y - bh.cy, pos.x - bh.cx);
// FIX THIS!!!
var g = 1;//(pixel_G * pixel_M) / (distance * distance * 1e2);
delta2.x += Math.cos(forceDirection2) * g;
delta2.y += Math.sin(forceDirection2) * g;
pos.x -= delta2.x;
pos.y -= delta2.y;
somethingMoved = true;
circles[i].color -= 1;
if (pos.x == bh.cx && pos.y == bh.cy) {
somethingMoved = false;
};
}
}
if (somethingMoved) {
drawEverything();
requestAnimationFrame(update);
};
}
function drawEverything() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
blackhole.draw(ctx);
for (var i = 0; i < circles.length; i++) {
circles[i].draw(ctx);
}
}
function init(event) {
canvas = document.getElementById("space");
canvas.width = bh.w;
canvas.height = bh.h;
ctx = canvas.getContext('2d');
blackhole = new Ball(5, { //pixel_Rs, {
x: bh.cx,
y: bh.cy
}, 0);
for (var i = 0; i < 200; i++) {
var vec2D = new Vector2D(Math.floor(Math.random() * bh.w), Math.floor(Math.random() * bh.h));
circle = new Ball(5, vec2D, ccolor);
circles.push(circle);
}
drawEverything();
requestAnimationFrame(update);
}
function Ball(radius, position, color) {
this.radius = radius;
this.position = position;
this.color = color;
}
Ball.prototype.draw = function(ctx) {
var c = parseInt(this.color);
ctx.fillStyle = 'rgba(' + c + ',' + c + ',' + c + ',1)';
ctx.beginPath();
ctx.arc(this.position.x, this.position.y, this.radius, 0, 2 * Math.PI);
ctx.closePath();
ctx.fill();
};
function Vector2D(x, y) {
this.x = x;
this.y = y;
}
function onClick() {
canvas = document.getElementById('space');
ctx = canvas.getContext('2d')
canvas.addEventListener("mousedown", init, false)
blackhole = new Ball(5, {
x: bh.cx,
y: bh.cy
}, 0);
blackhole.draw(ctx);
}
window.onload = onClick;
body {
background-color: #021c36;
margin: 0px;
}
<canvas id="space" , width="700" , height="400"></canvas>
For the last step of this project, I want the growing circle to stop when it collides with another circle. The isOnCircle function already checks for this successfully when creating a new circle. However, when adding the condition !isOnCircle to my grow() function (line 61) it prevents any new circles from being added.
function grow() {
var a = circles[circles.length - 1];
if (!isOnCircle(a)){
a.radius += 1;
}}
Perhaps the circle is being created first, then in the check for collision, it's colliding with itself. Where else could I put the !isOnCircle check so that it gets checked at every radius increase and stops the grow function then?
check this
//set up canvas
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var circles = [];
//create circle
function create(location) {
circles.push({
x: location.x,
y: location.y,
radius: 10,
color: '#' + Math.floor(Math.random() * 16777215).toString(16)
});
}
//figure out mouse position
var rect = document.getElementById("canvas").getBoundingClientRect();
// Get canvas offset on page
var offset = {
x: rect.left,
y: rect.top
};
function isOnCanvas(a) {
if ((a.x >= 0 && a.x <= rect.width) && (a.y >= 0 && a.y <= rect.height)) {
return true;
}
return false;
}
function isOnCircle(a) {
var i = 0,
l = circles.length,
x, y, d, c;
for (; i < l; ++i) {
c = circles[i];
x = a.x - c.x;
y = a.y - c.y;
d = (a.radius || 10) + c.radius;
if (x * x + y * y <= d * d) {
return true;
}
}
return false;
}
// draw all circles
function draw() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
for (var i = 0; i < circles.length; i++) {
var p = circles[i];
ctx.beginPath();
ctx.arc(p.x, p.y, p.radius, 0, 2 * Math.PI);
ctx.fillStyle = p.color;
ctx.fill();
}
}
//make last drawn circle 1px bigger
function grow() {
var a = circles[circles.length - 1];
a.radius += 1;
}
//find percentage of canvas filled in
var totalSpace = canvas.width * canvas.height;
var totalFilled = function () {
total = 0;
for (var i = 0; i < circles.length; i++) {
var p = circles[i];
total += Math.PI * Math.pow(p.radius, 2);
}
return total;
console.log(total);
}
function findPercentage() {
return (totalFilled() / totalSpace) * 100;
}
function updateInfo() {
percentage = findPercentage();
document.getElementById("percentage").innerHTML = "You've filled in " + percentage.toFixed(1) + "%";
}
//do all the stuff
var animate = function () {
grow();
draw();
updateInfo();
}
//put this outside function so we can stop it later
var growLoop;
window.onmousedown = function (e) {
// get event location on page offset by canvas location
var location = {
x: e.pageX - offset.x,
y: e.pageY - offset.y
};
if (isOnCanvas(location) && !isOnCircle(location)) {
create(location);
draw();
updateInfo();
growLoop = setInterval(animate, 100);
}
};
window.onmouseup = function () {
clearInterval(growLoop);
}
window.onmouseout = function () {
clearInterval(growLoop);
}
it's colliding with itself.
Probably. You definitely should avoid that in the collision detection:
function isOnCircle(a) {
var l = circles.length,
x, y, d, c;
for (var i = 0; i < l; ++i) {
c = circles[i];
if (a == c) // add these
continue; // two lines!
x = a.x - c.x;
y = a.y - c.y;
d = (a.radius || 10) + c.radius;
if (x * x + y * y <= d * d) {
return true;
}
}
return false;
}
It is colliding with itself. Since you know the current circle will always be the last one in circles you can modify isOnCircle like this:
l = circles.length - 1,
so that it won't check against the current circle.
http://jsfiddle.net/SeAGU/91/