Animated particle constellations


Ok, stop staring at those darn dots and start coding!

I saw animations similar to the one above on several websites and liked the simplicity of the concept, so let's recreate it - it will only take 42 lines of code.

At a high level, here's the recipe:

- a couple dozens of random particles are bouncing off of the edges of the Canvas
- calculate the distance between each pair of particles
- if the distance is lower than a pre-set threshold, draw a line between them

Here's the full code and a more detailed explanation is below.

<html>
<body bgcolor=black>
<canvas id="myCanvaswidth="800height="600"></canvas>
<script>
 
function line(particle, particle2) {
  context.beginPath();
  context.moveTo(particle.xparticle.y);
  context.lineTo(particle2.x, particle2.y);
  context.stroke();
}
 
function animate() {
  context.clearRect(00canvas.widthcanvas.height);
  for (let i = 0i < maxParticlesi++) {
    let particle = particles[i];
    context.fillRect(particle.x - particleSize / 2particle.y - particleSize / 2particleSizeparticleSize);
    for (let j = 0j < maxParticlesj++) {
      if (i != j) {
        let particle2 = particles[j];
        let distanceX = Math.abs(particle.x - particle2.x);
        let distanceY = Math.abs(particle.y - particle2.y);
        if (distanceX < threshold && distanceY < threshold) {
          context.lineWidth = ((threshold * 2) - (distanceX + distanceY)) / 50;
          let color = 200 - Math.floor(distanceX + distanceY);
          context.strokeStyle = 'rgb(' + color + ',' + color + ',' + color + ')';
          line(particle, particle2);
        }
      }
    }
    particle.x = particle.x + particle.vx;
    particle.y = particle.y + particle.vy;
    if (particle.x > canvas.width - particleSize || particle.x < particleSize)
      particle.vx = -particle.vx;
    if (particle.y > canvas.height - particleSize || particle.y < particleSize)
      particle.vy = -particle.vy;
  }
  window.requestAnimationFrame(animate);
}
 
let canvas = document.getElementById('myCanvas');
let context = canvas.getContext('2d');
let particles = [];
let particleSize = 4;
let maxParticles = 40;
let threshold = 100;
for (let i = 0i < maxParticlesi++) {
  let particle = {
    xMath.random() * canvas.width,
    yMath.random() * canvas.height,
    vxMath.random(),
    vyMath.random()
  }
  particles.push(particle);
}
context.fillStyle = 'white';
animate();
 
</script>
</body>
</html>


[1-4] HTML setup
[6-11] a function that draws a line between two particles
[13-39] the main animation function:
[14] clear the previous frame
[15-37] for each particle:
[18-27] check with every other particle
[19] make sure you're not checking a particle with itself
[21-22] calculate approximate distance between particles (a sum of differences in the X and Y axles). You could use the actual distance [sqrt(distanceX^2+distanceY^2)], but that just slows things down and is not really visible.
[23] if the distance is lower than the threshold...
[24] ...the width...
[25-26] ...and the color of the line (shade of gray with equal values of the Red, Green and Blue components) depend on the distance. Interestingly, Math.floor is only necessary for iOS - other platforms can handle float.
[31-32] The particle moves in both dimensions
[34-36] Bounce off of the edges
[41-46] Set up the Canvas and parameters.
[47-54] Initialize the particles with random coordinates and speeds.
[57] Action!

Experiment with different parameters, for example maxParticles = 100 and threshold = 40 gives you this:



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