We Keep Coding

Canavs is not drawing all the dots. Only one is showing up

In this script I’m trying to make a coordinate plane with two dots/circles. When I add the second dot in the code, it only shows the second one.
The part with the dots is this piece of code:
point(AX, AY, false, 'red', 6)
point(BX, BY, false, 'red', 6)
Can someone please help me with this problem? Thanks a lot!
start();
function start() {
console.clear();
document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var AX = document.getElementById("AX").value;
var AY = document.getElementById("AY").value;
var BX = document.getElementById("BX").value;
var BY = document.getElementById("BY").value;
var SQUARE_SIZE = 30;
var XSCALE = 1;
var YSCALE = 1;
var centerX = 0;
var centerY = 0;
selected = [];
points = [];
lines = [];
segments = [];
history = [];
circles = [];
function point(x, y, isSelected, color, r) {
this.x = x;
this.y = y;
this.color = color;
this.r = r;
this.add = function () {
plotPoint(this.x, this.y, this.color, this.r);
};
points.push(this);
if (isSelected) {
selected.push(this);
}
this.distance = function (gx, gy) {
return Math.sqrt(Math.pow(this.x - gx, 2) + Math.pow(this.y - gy, 2));
};
}
function point1(x, y, isSelected, color, r) {
this.x = x;
this.y = y;
this.color = color;
this.r = r;
this.add = function () {
plotPoint(this.x, this.y, this.color, this.r);
};
points.push(this);
if (isSelected) {
selected.push(this);
}
this.distance = function (gx, gy) {
return Math.sqrt(Math.pow(this.x - gx, 2) + Math.pow(this.y - gy, 2));
};
}
function circle(x, y, color, r) {
this.x = x;
this.y = y;
this.color = color;
this.r = r;
this.add = function () {
ctx.beginPath();
ctx.arc(convertX(x), convertY(y), r, 0, 2 * Math.PI);
ctx.stroke();
};
}
function line(m, b, color, width) {
this.m = m;
this.b = b;
this.color = color;
this.width = width;
lines.push(this);
}
function segment(a, b, color, width) {
this.a = a;
this.b = b;
this.color = color;
this.width = width;
this.getSlope = function () {
return (b.y - a.y) / (b.x - a.x);
};
this.getIntercept = function () {
var m = this.getSlope();
return a.y - m * a.x;
};
this.getLength = function () {
return Math.sqrt(this.a.x - this.b.x + this.a.y - this.b.y);
};
this.distance = function (gx, gy) {
//var m = (b.y-a.y)/(b.x-a.x)
//var bb = a.y-m*a.x
var m = this.getSlope();
var bb = this.getIntercept();
var pim = 1 / -m;
var pib = gy - pim * gx;
if (m === 0) {
pix = gx;
piy = this.a.y;
} else if (Math.abs(m) === Infinity) {
var pix = this.a.x;
var piy = gy;
} else {
var pix = (pib - bb) / (m - pim); //((gy-(gx/m)-bb)*m)/(m*m-1)
var piy = pim * pix + pib;
}
//console.log("m:"+m+" pim:"+pim+" pib:"+pib+" pix"+pix+" piy:"+piy)
if (
((this.a.x <= pix && pix <= this.b.x) ||
(this.b.x <= pix && pix <= this.a.x)) &&
((this.a.y <= piy && piy <= this.b.y) ||
(this.b.y <= piy && piy <= this.a.y))
) {
var d = Math.sqrt(Math.pow(gx - pix, 2) + Math.pow(gy - piy, 2));
return d;
} else {
var d = Math.min(this.a.distance(gx, gy), this.b.distance(gx, gy));
return d;
}
};
this.add = function () {
if (selected.indexOf(this) > -1) {
plotLine(this.a.x, this.a.y, this.b.x, this.b.y, color, width, [5, 2]);
} else {
plotLine(this.a.x, this.a.y, this.b.x, this.b.y, color, width);
}
};
segments.push(this);
}
// var a = new point(1,1)
// var b = new point(3,4)
// new segment(a,b)
//var testline = new line(1, 2, 'red', 1)
function drawLine(x1, y1, x2, y2, color, width, dash) {
ctx.save();
ctx.beginPath();
ctx.moveTo(x1, y1);
ctx.lineTo(x2, y2);
ctx.strokeStyle = color;
ctx.lineWidth = width;
if (dash !== undefined) {
ctx.setLineDash(dash);
}
ctx.stroke();
ctx.restore();
}
function convertX(x) {
return ((x - xmin - centerX) / (xmax - xmin)) * width;
}
function revertX(x) {
return (x * (xmax - xmin)) / width + centerX + xmin;
}
function convertY(y) {
return ((ymax - y - centerY) / (ymax - ymin)) * height;
}
function revertY(y) {
return (y * (ymin - ymax)) / height - centerY - ymin;
}
function addAxis() {
var TICK = 0;
for (
var i = Math.floor(xmin + centerX);
i <= Math.floor(xmax + centerX);
i += XSCALE
) {
drawLine(
convertX(i),
convertY(0) + TICK,
convertX(i),
convertY(0) - TICK
);
}
for (
var i = Math.floor(ymin - centerY);
i <= Math.floor(ymax - centerY);
i += YSCALE
) {
drawLine(
convertX(0) - TICK,
convertY(i),
convertX(0) + TICK,
convertY(i)
);
}
}
function addGrid() {
for (
var i = Math.floor(ymin - centerY);
i <= Math.floor(ymax - centerY);
i += YSCALE
) {
drawLine(0, convertY(i), width, convertY(i), "lightgrey", 1);
}
for (
var i = Math.floor(xmin + centerX);
i <= Math.floor(xmax + centerX);
i += XSCALE
) {
drawLine(convertX(i), height, convertX(i), 0, "lightgrey", 1);
}
}
function addPoints() {
for (const p of points) {
p.add();
}
}
function addCircles() {
for (const c of circles) {
c.add();
}
}
function addLines() {
for (const l of lines) {
plotLine(
xmin + centerX,
l.m * (xmin + centerX) + l.b,
xmax + centerX,
l.m * (xmax + centerX) + l.b,
l.color,
l.width
);
}
}
function addSegments() {
for (const s of segments) {
s.add();
}
}
function plotPoint(x, y, color, r) {
if (r === undefined) {
r = 2;
}
if (color === undefined) {
color = "black";
}
ctx.fillStyle = color;
ctx.beginPath();
ctx.arc(convertX(x), convertY(y), r, 0, 2 * Math.PI);
ctx.fill();
}
function plotCircle(x, y, color, r) {
if (r === undefined) {
r = 2;
}
if (color === undefined) {
color = "black";
}
ctx.beginPath();
ctx.arc(convertX(x), convertY(y), r, 0, 2 * Math.PI);
ctx.stroke();
}
function plotLine(x1, y1, x2, y2, color, width, dash) {
ctx.save();
ctx.beginPath();
ctx.moveTo(convertX(x1), convertY(y1));
ctx.lineTo(convertX(x2), convertY(y2));
ctx.strokeStyle = color;
ctx.lineWidth = width;
if (dash !== undefined) {
ctx.setLineDash(dash);
}
ctx.stroke();
ctx.restore();
}
function snap(x) {
if ((x - Math.round(x)) * (x - Math.round(x)) < 0.01) {
return Math.round(x);
} else {
return x;
}
}
function mouseDown(evt) {
x = evt.clientX;
y = evt.clientY;
ocx = centerX;
ocy = centerY;
if (evt.buttons === 2) {
for (const p of points) {
if (
nx * nx - 2 * convertX(p.x) * nx + convertX(p.x) * convertX(p.x) <
36 &&
ny * ny - 2 * convertY(p.y) * ny + convertY(p.y) * convertY(p.y) < 36
) {
s = new segment(p, new point(revertX(x), revertY(y), true));
selected.push(s);
return;
}
}
new point(snap(revertX(x)), snap(revertY(y)));
}
if (evt.buttons === 1) {
for (const p of points) {
if (p.distance(revertX(x), revertY(y)) < 0.2) {
selected.push(p);
}
console.log(p.distance(revertX(x), revertY(y)));
}
for (const s of segments) {
if (s.distance(revertX(x), revertY(y)) < 0.2) {
selected.push(s);
}
console.log(s.distance(revertX(x), revertY(y)));
}
}
onresize();
}
function mouseUp() {
selected = [];
}
function mouseMove(evt) {
console.clear();
nx = evt.clientX;
ny = evt.clientY;
gx = revertX(nx);
gy = revertY(ny);
if (evt.buttons === 1) {
if (selected.length > 0) {
for (const p of selected) {
p.x = snap(gx);
p.y = snap(gy);
}
} else {
centerX = (x - nx) / SQUARE_SIZE + ocx;
centerY = (y - ny) / SQUARE_SIZE + ocy;
}
}
if (evt.buttons === 2) {
for (const p of selected) {
p.x = snap(gx);
p.y = snap(gy);
}
}
console.log("coords: " + gx + ", " + gy);
console.log("points: " + points);
console.log("segments:" + segments);
console.log("selected: " + selected);
onresize();
}
function keyPress(evt) {
if ((evt.keyCode = 32)) {
//space
if (selected.length > 0) selected = [];
}
onresize();
}
point(AX, AY, false, "red", 6);
point(BX, BY, false, "red", 6);
window.onresize = function () {
width = canvas.width = window.innerWidth;
height = canvas.height = window.innerHeight;
xmin = -width / SQUARE_SIZE / 2;
xmax = width / SQUARE_SIZE / 2;
ymin = -height / SQUARE_SIZE / 2;
ymax = height / SQUARE_SIZE / 2;
addGrid();
addAxis();
addPoints();
addLines();
addSegments();
addCircles();
ctx.font = "12px Arial";
ctx.fillStyle = "black";
ctx.fillText("Number of Points: " + points.length, 20, 30);
ctx.fillText("Points Slected: " + selected.length, 20, 50);
};
onresize();
}
<h2>LocusCreator v1.0 - © Niels Langerak</h2>
<p>Use the inputboxes to fill in all the info to make the locus.</p>
<p>Circle A - X:</p>
<input type="number" id="AX" value="0">
<p>Circle A - Y:</p>
<input type="number" id="AY" value="0">
<p>Circle B - X:</p>
<input type="number" id="BX" value="1">
<p>Circle B - Y:</p>
<input type="number" id="BY" value="1">
<button onclick="start()">Reload</button>
<canvas width=600px height=600px id='canvas'>

You should use the new keyword when creating your point:
new point(AX, AY, false, 'red', 6)
new point(BX, BY, false, 'red', 6)
It creates a new instance of point, but not overwrite it, as it works in your code.

Is there an error in the way this simulation calculates gravitational attraction and body collision?

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).

Invert direction of game

I am developing a basic game where the user needs to go through the openings and avoid crashing with the obstacles. My issue now is that the flow of the game is from the bottom to the top, when in fact I need the obstacles to come from the top to the bottom.
What am I missing in the code? Any help is appreciated.
let myObstacles = [];
let myGameArea = {
canvas: document.createElement("canvas"),
frames: 0,
start: function() {
this.canvas.width = 700;
this.canvas.height = 500;
this.context = this.canvas.getContext("2d");
this.canvas.classList.add('canvasBg');
document.body.insertBefore(this.canvas, document.body.childNodes[0]);
this.interval = setInterval(updateGameArea, 20);
},
clear: function() {
this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
},
stop: function() {
clearInterval(this.interval);
},
score: function() {
var points = Math.floor(this.frames / 5);
this.context.font = "18px serif";
this.context.fillStyle = "black";
this.context.fillText("Score: " + points, 350, 50);
}
}
class Component {
constructor(width, height, color, x, y) {
this.width = width;
this.height = height;
this.color = color;
this.x = x;
this.y = y;
this.speedX = 0;
this.speedY = 0;
}
update() {
let ctx = myGameArea.context;
ctx.fillStyle = this.color;
ctx.fillRect(this.x, this.y, this.width, this.height);
}
newPos() {
this.x += this.speedX;
this.y += this.speedY;
}
left() {
return this.x;
}
right() {
return this.x + this.width;
}
top() {
return this.y;
}
bottom() {
return this.y + this.height;
}
crashWith(obstacle) {
return !(
this.bottom() < obstacle.top() ||
this.top() > obstacle.bottom() ||
this.right() < obstacle.left() ||
this.left() > obstacle.right()
);
}
}
function checkGameOver() {
let crashed = myObstacles.some(function(obstacle) {
return player.crashWith(obstacle);
});
if (crashed) {
myGameArea.stop();
}
}
document.onkeydown = function(e) {
switch (e.keyCode) {
case 38: // up arrow
player.speedY -= 1;
break;
case 40: // down arrow
player.speedY += 1;
break;
case 37: // left arrow
player.speedX -= 1;
break;
case 39: // right arrow
player.speedX += 1;
break;
}
};
function updateObstacles() {
for (i = 0; i < myObstacles.length; i++) {
myObstacles[i].y += -3;
myObstacles[i].update();
}
myGameArea.frames += 1;
if (myGameArea.frames % 60 === 0) {
let x = myGameArea.canvas.width;
let y = myGameArea.canvas.height;
let minWidth = 20;
let maxWidth = 200;
let width = Math.floor(
Math.random() * (maxWidth - minWidth + 1) + minWidth
);
var minGap = 70;
var maxGap = 200;
var gap = Math.floor(Math.random() * (maxGap - minGap + 1) + minGap);
myObstacles.push(new Component(width, 10, "green", 0, y));
myObstacles.push(
new Component(y-width-gap, 10, "green", width+gap, y)
);
}
}
document.onkeyup = function(e) {
player.speedX = 0;
player.speedY = 0;
};
function updateGameArea() {
myGameArea.clear();
player.newPos();
player.update();
updateObstacles();
checkGameOver();
myGameArea.score();
};
myGameArea.start();
let player = new Component(30, 30, "red", 0, 110);

I got it to work by changing 3 things in your updateObstacles function.
First, change myObstacles[i].y += -3 to myObstacles[i].y += 3
Second, change let y = myGameArea.canvas.height to let y = 0
Third, change
new Component(y-width-gap, 10, "green", width+gap, y)
to
new Component(x-width-gap, 10, "green", width+gap, y)
Full code:
function updateObstacles() {
for (i = 0; i < myObstacles.length; i++) {
myObstacles[i].y += 3;
myObstacles[i].update();
}
myGameArea.frames += 1;
if (myGameArea.frames % 60 === 0) {
let x = myGameArea.canvas.width;
let y = 0;
let minWidth = 20;
let maxWidth = 200;
let width = Math.floor(
Math.random() * (maxWidth - minWidth + 1) + minWidth
);
var minGap = 70;
var maxGap = 200;
var gap = Math.floor(Math.random() * (maxGap - minGap + 1) + minGap);
myObstacles.push(new Component(width, 10, "green", 0, y));
myObstacles.push(
new Component(x-width-gap, 10, "green", width+gap, y)
);
}
}
Example jsfiddle

Javascript line and point angle collision

I want to move the balls in correct direction when bat collide with them, like in this example
It doesn't have to be this good though. Working correctly is the goal here.
So far, what I've got can be seen in the following url:
https://jsfiddle.net/qphqvntx/4/
The problem is with the collision, when bat hit the balls. It's behaving very weird.
//Canvas Variable
var mainCanvas = document.getElementById("mainCanvas");
var ctx = mainCanvas.getContext("2d");
var canvasHeight = mainCanvas.height;
var canvasWidth = mainCanvas.width;
var borderRadius = 10;
var bottomRadius = 120;
var gravity = 0.2;
var animate = false;
//Ball Object related variable
var balls = [];
var ballObj = {
x: 0,
y: 0,
velocity: {x: 0, y: 0},
};
var ball = '';
var debugBall = '';
var ballRadius = 10;
var dumping = 0.99;
var ballSpeed = 6;
var force = 1.8;
var setBallTimer = 150;
var updateBallTimer = 0;
var target;
var distanceX;
var distancey;
var j, balls2;
//Bat related variable
var batXPos = 200;
var batYPos = canvasHeight - bottomRadius - 120;
var batHeight = 100;
var batWidth = 10;
var mouse = [0, 0];
var point = [170, 175];
var dx, dy;
//run related variable
var oneRunLine = 60;
var twoRunLine = 90;
var fourRunLine = 100;
var outTopLine = 450;
var oneRunChain = canvasHeight - bottomRadius;
var twoRunChain = canvasHeight - bottomRadius - oneRunLine;
var fourRunChain = canvasHeight - bottomRadius - oneRunLine - twoRunLine;
var sixRunChain = canvasHeight - bottomRadius - oneRunLine - twoRunLine - fourRunLine;
var circleUnderMouse;
var mouse = {
x: 0,
y: 0,
down: false
}
var res;
var previousEvent = false;
function executeFrame() {
if (animate) {
requestAnimFrame(executeFrame);
}
ctx.lineWidth = "3";
ctx.strokeRect(0, 0, mainCanvas.width, mainCanvas.height);
ctx.strokeRect(0, 0, mainCanvas.width, mainCanvas.height - bottomRadius);
ctx.fillStyle = 'rgba(255,255,255,0.3)';
ctx.fillRect(0, 0, mainCanvas.width, mainCanvas.height);
update();
if (balls.length != '0') {
balls.forEach(function (ball, j, i) {
drawBall(ball);
createBat();
});
}
}
initializeGame();
function update() {
if (balls.length != '0') {
balls.forEach(function (ball, balli, ballj) {
ball.addGravity();
ball.velocity.y *= dumping;
ball.velocity.x *= dumping;
ball.y += ball.velocity.y;
ball.x += ball.velocity.x * force;
if (hitGround(ball) == true) {
ball.y = mainCanvas.height - bottomRadius;
ball.velocity.y = -Math.abs(ball.velocity.y);
}
if (hitLeft(ball) == true) {
ball.velocity.x = Math.abs(ball.velocity.x);
}
var hit = linePoint(point[0], point[1], mouse[0], mouse[1], ball.x, ball.y, ball);
if (hit == true) {
//console.log("hit");
} else {
//console.log("not yet");
}
for (j = balli + 1; j < balls.length; j++) {
balls2 = ballj[j];
var dx = balls2.x - ball.x;
var dy = balls2.y - ball.y;
var d = Math.sqrt(dx * dx + dy * dy);
if (d < 2 * ballRadius) {
if (d === 0) {
d = 0.1;
}
var unitX = dx / d;
var unitY = dy / d;
var newForce = -1;
var forceX = unitX * newForce;
var forceY = unitY * newForce;
ball.velocity.x += forceX;
ball.velocity.y += forceY;
balls2.velocity.x -= forceX;
balls2.velocity.y -= forceY;
}
}
});
}
updateBallTimer++;
if (updateBallTimer >= setBallTimer) {
createBall();
updateBallTimer = 0;
}
}
function initializeGame() {
createBall();
createBat();
}
function createBall() {
randomPoint(50, 150);
ball = instantiateBall(canvasWidth, target.y, ballObj);
ball.velocity.x -= getRandomNumber(4, 6);
}
function instantiateBall(xPos, yPos, ball) {
ball = {
x: xPos,
y: yPos,
velocity: {x: 0, y: 0},
addGravity: function () {
return this.velocity.y += gravity;
},
onCanvas: false
};
balls.push(ball);
drawBall(ball);
return ball;
}
function drawBall(ball) {
if (ball != '') {
ctx.beginPath();
ctx.arc(ball.x, ball.y, ballRadius, 0, 2 * Math.PI, false);
ctx.fillStyle = "#000";
ctx.fill();
}
}
function createBat() {
// ctx.clearRect(0, 0, width, height)
dx = mouse[0] - point[0],
dy = mouse[1] - point[1];
rot = Math.atan2(dy, dx);
ctx.fillStyle = 'red';
ctx.fillRect(point[0], point[1], 10, 10);
ctx.fillStyle = 'gray';
ctx.save();
ctx.translate(point[0], point[1]);
ctx.rotate(rot);
ctx.fillRect(0, 0, batHeight, batWidth);
ctx.moveTo(point[0], point[1]);
ctx.lineTo(point[0] + (mouse[0] - point[0]) + 0.5, point[1] + (mouse[1] - point[1]) * 0.5);
//ctx.stroke();
ctx.restore();
}
function linePoint(x1, y1, x2, y2, px, py, ball) {
var d1 = dist(px, py, x1, y1);
var d2 = dist(px, py, x2, y2);
var lineLen = dist(x1, y1, x2, y2);
var buffer = 3;
var batAngle = Math.atan2(d2, d1);
var batAngleX = Math.sin(batAngle);
var batAngleY = -Math.cos(batAngle);
if (d1 + d2 >= lineLen - buffer && d1 + d2 <= lineLen + buffer) {
var d = 2 * (ball.velocity.x * batAngleX + ball.velocity.y * batAngleY);
ball.x -= d * batAngleX;
ball.x -= d * batAngleY;
ball.velocity.x -= d * batAngleX + res;
ball.velocity.y -= d * batAngleY + res;
return true;
}
return false;
}
function dist(x1, y1, x2, y2) {
var xs = x2 - x1,
ys = y2 - y1;
xs *= xs;
ys *= ys;
return Math.sqrt(xs + ys);
}
function getRandomNumber(min, max) {
return Math.random() * (max - min) + min;
}
function randomPoint(min, max) {
var rndNum = Math.random() * (max - min) + min;
target = {
x: canvasWidth,
y: rndNum
};
// ctx.beginPath();
// ctx.arc(rndNum, canvasHeight, ballRadius, 0, 2 * Math.PI, false);
// ctx.fillStyle = "#ff0";
// ctx.fill();
}
function isOnCanvas(obj) {
if (obj.x <= mainCanvas.width && obj.y <= mainCanvas.height - bottomRadius) {
return true;
}
return false;
}
function hitGround(obj) {
if (obj.y >= mainCanvas.height - bottomRadius) {
//console.log("hit the ground");
return true;
}
return false;
}
function hitTop(obj) {
if (obj.y <= borderRadius) {
//console.log("hit the top");
return true;
}
return false;
}
function hitLeft(obj) {
if (obj.x <= borderRadius) {
//console.log("hit the left");
return true;
}
return false;
}
function hitRight(obj) {
if (obj.x >= mainCanvas.width - borderRadius) {
//console.log("hit the left");
return true;
}
return false;
}
function drawLineRandomPoint(moveX, moveY, lineX, lineY, strColor) {
ctx.beginPath();
ctx.moveTo(moveX, moveY);
ctx.lineTo(lineX, lineY);
ctx.strokeStyle = strColor;
ctx.stroke();
}
mainCanvas.addEventListener('mousemove', function (e) {
e.time = Date.now();
res = makeVelocityCalculator(e, previousEvent);
previousEvent = e;
mouse[0] = e.clientX;
mouse[1] = e.clientY;
});
function makeVelocityCalculator(e_init, e) {
var x = e_init.clientX, new_x, new_y, new_t,
x_dist, y_dist, interval, velocity,
y = e_init.clientY,
t;
if (e === false) {
return 0;
}
t = e.time;
new_x = e.clientX;
new_y = e.clientY;
new_t = Date.now();
x_dist = new_x - x;
y_dist = new_y - y;
interval = new_t - t;
// update values:
x = new_x;
y = new_y;
velocity = Math.sqrt(x_dist * x_dist + y_dist * y_dist) / interval;
return velocity;
}
mainCanvas.addEventListener('mouseover', function (e) {
animate = true;
executeFrame();
});
mainCanvas.addEventListener("mouseout", function (e) {
animate = false;
});
executeFrame();
window.requestAnimFrame = (function () {
return window.requestAnimationFrame ||
window.webkitRequestAnimationFrame ||
window.mozRequestAnimationFrame ||
window.oRequestAnimationFrame ||
window.msRequestAnimationFrame ||
function (callback) {
window.setTimeout(callback, 1000 / 60);
};
})();
<body>
<canvas id="mainCanvas" height="400" width="600"></canvas>
<script src="main.js" type="text/javascript"></script>
</body>

How to stop line colouring over transparent canvas?

I need some expert help. When I make canvas background transparent the line colors the whole canvas (shown in code below).
How do I stop/fix this? I want the line stay as a single line that doesn't color the canvas.
Math.clamp = function(x, min, max) {
return x < min ? min : (x > max ? max : x);
};
// canvas settings
var viewWidth = window.innerWidth,
viewHeight = window.innerHeight,
drawingCanvas = document.getElementById("drawing_canvas"),
ctx,
timeStep = (10 / 100),
time = 0;
var lineTension = 0.067,
lineDamping = 0.068,
waveSpreadFactor = 0.1;
var previousMousePosition = {
x: 0,
y: 0
},
currentMousePosition = {
x: 0,
y: 0
},
actualMousePosition = {
x: 0,
y: 0
};
var line,
lineSegmentCount = 64,
lineMaxForce = 32,
lineStrokeGradient;
var audioCtx,
nodeCount = 64,
oscillatorNodes = [],
gainNodes = [];
var segmentsPerNode = lineSegmentCount / nodeCount;
function initGui() {
}
function goBananas() {
lineTension = 0.2;
line.anchors[Math.floor(Math.random() * line.anchors.length)].
vel = lineMaxForce;
}
function resetLine() {
line.reset();
for (var i = 0; i < nodeCount; i++) {
oscillatorNodes[i].detune.value = 100;
gainNodes[i].gain.value = 0;
}
lineTension = 0.0025;
lineDamping = 0.05;
waveSpreadFactor = 0.1;
}
function initDrawingCanvas() {
drawingCanvas.width = viewWidth;
drawingCanvas.height = viewHeight;
window.addEventListener('resize', resizeHandler);
window.addEventListener('mousemove', mouseMoveHandler);
setInterval(updateMousePosition, (1000 / 30));
ctx = drawingCanvas.getContext('2d');
ctx.lineWidth = 5;
line = new Line(0, viewHeight * 0.5, viewWidth, lineSegmentCount);
// line.anchors[0].vel = viewHeight * 0.25;
lineStrokeGradient = ctx.createLinearGradient(0, 0, 0, viewHeight);
lineStrokeGradient.addColorStop(0, '#0ff');
}
function initWebAudio() {
audioCtx = new(window.AudioContext || window.webkitAudioContext)();
for (var i = 0; i < nodeCount; i++) {
var oscillatorNode = audioCtx.createOscillator();
var gainNode = audioCtx.createGain();
oscillatorNode.connect(gainNode);
gainNode.connect(audioCtx.destination);
gainNode.gain.value = 0;
oscillatorNode.type = 'saw';
oscillatorNode.detune.value = 200;
oscillatorNode.frequency.value = 1200 * (i / 60);
oscillatorNode.start();
oscillatorNodes[i] = oscillatorNode;
gainNodes[i] = gainNode;
}
}
function resizeHandler() {
drawingCanvas.width = viewWidth = window.innerWidth;
drawingCanvas.height = viewHeight = window.innerHeight;
if (ctx) {
ctx.lineWidth = 4;
line.resize(viewWidth, viewHeight * 0.5);
}
}
function mouseMoveHandler(event) {
actualMousePosition.x = Math.floor(event.clientX);
actualMousePosition.y = Math.floor(event.clientY);
}
function updateMousePosition() {
previousMousePosition.x = currentMousePosition.x;
previousMousePosition.y = currentMousePosition.y;
currentMousePosition.x = actualMousePosition.x;
currentMousePosition.y = actualMousePosition.y;
}
function update() {
var px = Math.min(previousMousePosition.x, currentMousePosition.x),
py = Math.min(previousMousePosition.y, currentMousePosition.y),
pw = Math.max(1, Math.abs(previousMousePosition.x - currentMousePosition.x)),
ph = Math.max(1, Math.abs(previousMousePosition.y - currentMousePosition.y)),
force = Math.clamp(currentMousePosition.y -
previousMousePosition.y, -lineMaxForce, lineMaxForce);
var pixels = ctx.getImageData(px, py, pw, ph),
data = pixels.data;
for (var i = 0; i < data.length; i += 3) {
var r = data[i + 0],
g = data[i + 1],
b = data[i + 2],
x = (i % ph) + px;
if (r + g + b > 0) {
line.ripple(x, force);
}
}
line.update();
for (var j = 0; j < gainNodes.length; j++) {
var anchor = line.anchors[j * segmentsPerNode],
gain = Math.clamp(Math.abs(anchor.vel) / viewHeight * 0.5, 0, 3),
detune = Math.clamp(anchor.pos / viewHeight * 100, 0, 300);
gainNodes[j].gain.value = gain;
oscillatorNodes[j].detune.value = detune;
}
}
function draw() {
ctx.strokeStyle = lineStrokeGradient;
line.draw();
}
window.onload = function() {
initDrawingCanvas();
initWebAudio();
initGui();
requestAnimationFrame(loop);
};
function loop() {
update();
draw();
time += timeStep;
requestAnimationFrame(loop);
}
Line = function(x, y, length, segments) {
this.x = x;
this.y = y;
this.length = length;
this.segments = segments;
this.segmentLength = this.length / this.segments;
this.anchors = [];
for (var i = 0; i <= this.segments; i++) {
this.anchors[i] = {
target: this.y,
pos: this.y,
vel: 0,
update: function() {
var dy = this.pos - this.target,
acc = -lineTension * dy - lineDamping * this.vel;
this.pos += this.vel;
this.vel += acc;
},
reset: function() {
this.pos = this.target;
this.vel = 0;
}
};
}
};
Line.prototype = {
resize: function(length, targetY) {
this.length = length;
this.segmentLength = this.length / this.segments;
for (var i = 0; i <= this.segments; i++) {
this.anchors[i].target = targetY;
}
},
reset: function() {
for (var i = 0; i <= this.segments; i++) {
this.anchors[i].reset();
}
},
ripple: function(origin, amplitude) {
var i = Math.floor((origin - this.x) / this.segmentLength);
if (i >= 0 && i <= this.segments) {
this.anchors[i].vel = amplitude;
}
},
update: function() {
var lDeltas = [],
rDeltas = [],
i;
for (i = 0; i <= this.segments; i++) {
this.anchors[i].update();
}
for (i = 0; i <= this.segments; i++) {
if (i > 0) {
lDeltas[i] = waveSpreadFactor * (this.anchors[i].pos - this.anchors[i - 1].pos);
this.anchors[i - 1].vel += lDeltas[i];
}
if (i < this.segments) {
rDeltas[i] = waveSpreadFactor * (this.anchors[i].pos - this.anchors[i + 1].pos);
this.anchors[i + 1].vel += rDeltas[i];
}
}
for (i = 0; i <= this.segments; i++) {
if (i > 0) {
this.anchors[i - 1].pos += lDeltas[i];
}
if (i < this.segments) {
this.anchors[i + 1].pos += rDeltas[i];
}
}
},
draw: function() {
ctx.beginPath();
for (var i = 0; i <= this.segments; i++) {
ctx.lineTo(
this.x + this.segmentLength * i,
this.anchors[i].pos
);
}
ctx.stroke();
}
};

From the code you posted, the problem seems to be a missing
ctx.clearRect(0, 0, viewWidth, viewHeight)
at the beginning of your "draw" function.
See a working example here