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Title	Atomic simulation
ID	1064545094
Created	13 years ago, 1352747462100
Updated	11 years ago, 1391807310231
Code	/********************************************************* * Modelling diffusion. * Particles bounce off one another and the walls * * Need to fix wall bouncing ********************************************************/ // Physical variables to play with var gravity = 0; // Force due to gravity // Atom properties var initialSpeed = 1; // Equivalent to temperature var numAtoms = 100; var atomSize = 5; // Wall properties var wallX = 200; var gapSize = 50; var wallY1 = (height - gapSize) / 2; var wallY2 = (height + gapSize) / 2; var colour1 = color(40, 60, 160, 200); var colour2 = color(160, 60, 40, 200); textAlign(CENTER, CENTER); textSize(15); var dotProduct = function(ax, ay, bx, by) { return ax bx + ay * by; }; // Particles have a position, speed, colour and masss var Particle = function(x, y, r, c, mass) { // Position this.x = x; this.y = y; // Radius this.r = r; this.mass = mass \|\| this.r * this.r; // Colour this.c = c; // Velocity this.dx = initialSpeed * (random() - 0.5); this.dy = initialSpeed * (random() - 0.5); }; Particle.prototype.draw = function() { fill(this.c); ellipse(this.x, this.y, this.r * 2, this.r * 2); }; // Move ball based on its velocity Particle.prototype.move = function() { this.x += this.dx; this.y += this.dy; }; Particle.prototype.collide = function(that) { var dx = this.x - that.x; var dy = this.y - that.y; var dr = this.r + that.r; var d = dx * dx + dy * dy; if (d < dr * dr) { // Particles collide var collisionDist = sqrt(d + 1); // Find unit vector in direction of collision var collisionVi = dx / collisionDist; var collisionVj = dy / collisionDist; // Find velocity of particle projected on to collision vector var collisionV1 = dotProduct(this.dx, this.dy, dx, dy) / collisionDist; var collisionV2 = dotProduct(that.dx, that.dy, dx, dy) / collisionDist; // Find velocity of particle perpendicular to collision vector var perpV1 = dotProduct(this.dx, this.dy, -dy, dx) / collisionDist; var perpV2 = dotProduct(that.dx, that.dy, -dy, dx) / collisionDist; // Find movement in direction of collision var sumMass = this.mass + that.mass; var diffMass = this.mass - that.mass; var v1p = (diffMass * collisionV1 + 2 * that.mass * collisionV2) / sumMass; var v2p = (2 * this.mass * collisionV1 - diffMass * collisionV2) / sumMass; // Update velocities this.dx = v1p * collisionVi - perpV1 * collisionVj; this.dy = v1p * collisionVj + perpV1 * collisionVi; that.dx = v2p * collisionVi - perpV2 * collisionVj; that.dy = v2p * collisionVj + perpV2 * collisionVi; // Move to avoid overlap var overlap = dr + 1 - collisionDist; this.x += collisionVi * overlap; this.y += collisionVj * overlap; that.x -= collisionVi * overlap; that.y -= collisionVj * overlap; } }; // Bounce off walls Particle.prototype.bounce = function() { // Magnitude of velocity //var temp = dist(0, 0, this.dx, this.dy); //var dtemp = (temp + wallTemp) / (2 * temp); if (this.x < this.r) { this.x = this.r; this.dx = -1; //this.dx = -dtemp; } if (this.x > width - this.r){ this.x = width - this.r; this.dx = -1; //this.dx = -dtemp; } if (this.y < this.r) { this.y = this.r; this.dy = -1; //this.dy = -dtemp; } if (this.y > height - this.r){ this.y = height - this.r; this.dy = -1; //this.dy = -dtemp; } // Bounce off central wall var notInGap = (this.y - this.r <= wallY1 \|\| this.y + this.r >= wallY2); if (this.x + this.r > wallX && this.x - this.dx + this.r < wallX && notInGap) { this.dx = -1; this.x = 2 wallX - this.x - this.r * 2; } else if (this.x - this.r < wallX && this.x - this.dx - this.r > wallX && notInGap) { this.dx = -1; this.x = 2 wallX - this.x + this.r * 2; } }; // Test whether mouse is over ball Particle.prototype.selected = function() { return dist(mouseX, mouseY, this.x, this.y) < this.r; }; var initialiseParticlePositions = function(n) { var balls = []; // Blue balls on the left side for (var b = 0; b < n / 2; b++) { var y = atomSize + round(random() * (400 - 2 * atomSize)); var x = atomSize + round(random() * (200 - 2 * atomSize)); balls.push(new Particle(x, y, atomSize, colour1)); } // Red balls on the right for (var b = 0; b < n / 2; b++) { var y = atomSize + round(random() * (400 - 2 * atomSize)); var x = 200 + atomSize + round(random() * (200 - 2 * atomSize)); balls.push(new Particle(x, y, atomSize, colour2)); } return balls; }; var balls = initialiseParticlePositions(numAtoms); var skip = 3; frameRate(60); var drawInfo = function() { var countLeft1 = 0; var countLeft2 = 0; var countRight1 = 0; var countRight2 = 0; for (var i = 0; i < balls.length; i++) { if (balls[i].x < wallX) { if (balls[i].c === colour1) { countLeft1++; } else { countLeft2++; } } else { if (balls[i].c === colour1) { countRight1++; } else { countRight2++; } } } var w = 120; var pLeft = countLeft1 / (countLeft1 + countLeft2); var pRight = countRight1 / (countRight1 + countRight2); var pLeftW = round(w * pLeft); var pRightW = round(w * pRight); noStroke(); fill(0, 0, 0, 100); rect(41, 12, w + 1, 30); rect(241, 12, w + 1, 30); strokeWeight(1); stroke(10); fill(255); rect(39, 10, w + 1, 30); rect(239, 10, w + 1, 30); noStroke(); fill(colour1); rect(40, 11, pLeftW, 29); rect(240, 11, pRightW, 29); fill(colour2); rect(40 + pLeftW, 11, w - pLeftW, 29); rect(240 + pRightW, 11, w - pRightW, 29); fill(255); text(round(100 * pLeft) + "% Blue", 40 + w/2, 25); text(round(100 * pRight) + "% Blue", 240 + w/2, 25); }; var draw = function() { background(250, 245, 240); // Wall strokeWeight(3); stroke(80); line(wallX, 0, wallX, (height - gapSize)/2); line(wallX, (height + gapSize)/2, wallX, height); noStroke(); for (var i = 0; i < numAtoms; i++) { balls[i].draw(); } for (var t = 0; t < skip; t++) { // Calculate acceleration for (var i = 0; i < numAtoms; i++) { balls[i].dy += gravity; for (var j = i + 1; j < numAtoms; j++){ balls[i].collide(balls[j]); } } // Move balls for (i = 0; i < numAtoms; i++) { var ball = balls[i]; ball.move(); ball.bounce(); } } drawInfo(); };
Folds
Fork	false
Key	ag5zfmtoYW4tYWNhZGVteXIUCxIKU2NyYXRjaHBhZBjG1s77Aww
Votes	194
Spin-Offs	38
Type	PJS
Width	400
Height	400
User Flagged	false
Origin Scratchpad	{"id":"966544138","title":"Bouncing balls","deleted":"false","official":"false"}
Hidden From Hotlist	false
Restricted Posting	false
By Child	false
Author Nick	Peter Collingridge
Author Name	peterwcollingridge
Author ID	kaid_1128810778687926889052316
Author Profile Access	COACH

Archive Data

Added	10 months ago, 1739279680282
Updated	10 months ago, 1739279680282
Source Deleted	unknown