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POHow to avoid particles glitching together in an elastic particle collision simulator?
 

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  1. POHow to avoid particles glitching together in an elastic particle collision simulator?
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    <p>Here is a <a href="http://www.youtube.com/watch?v=wN8u-ERVaww" rel="nofollow">short video</a> in which can be seen that groups of two (maybe more) particles are glitched into each other.</p> <p>The source-code can be found <a href="https://github.com/fibonatic/particleSim" rel="nofollow">here</a>.</p> <p>And this is the code I use to calculate the collisions with:</p> <pre><code>function collisionPhysics() { for (var i = 0; i &lt; N - 1; ++i) { for (var j = i + 1; j &lt; N; ++j) { var Dx = objects[j].x - objects[i].x; // Difference in X direction between objects[i] and objects[j]. var Dy = objects[j].y - objects[i].y; // Difference in Y direction between objects[i] and objects[j]. var D2 = Dx * Dx + Dy * Dy; // Distance between objects[i] and objects[j] squared. if (D2 &lt;= (objects[i].rad + objects[j].rad) * (objects[i].rad + objects[j].rad)) // Colision check could be inserted here, reusing D2. { var delta = 2 * (Dx * (objects[i].Vx - objects[j].Vx) + Dy * (objects[i].Vy - objects[j].Vy)) / (D2 * (objects[i].m + objects[j].m)); objects[i].Vx += -objects[i].m * delta * Dx; objects[i].Vy += -objects[i].m * delta * Dy; objects[j].Vx += objects[j].m * delta * Dx; objects[j].Vy += objects[j].m * delta * Dy; } } } } </code></pre> <p><strong>Edit 2013/04/06:</strong> The issue nwellcome mentioned was causing the strange behavior. And this adjusted function should solve this, not sure if it could be improve performance wise but it works:</p> <pre><code>function collisionPhysics() { for (var i = 0; i &lt; N - 1; ++i) { for (var j = i + 1; j &lt; N; ++j) { var Dx = objects[j].x - objects[i].x + timeStep * (objects[j].u - objects[i].u); var Dy = objects[j].y - objects[i].y + timeStep * (objects[j].v - objects[i].v); var D2 = Dx * Dx + Dy * Dy; // Distance between objects[i] and objects[j] squared. if (D2 &lt;= (objects[i].r + objects[j].r) * (objects[i].r + objects[j].r)) // Colision check could be inserted here, reusing D2. { objects[i].col = true; objects[j].col = true; var dx = objects[j].x - objects[i].x; var dy = objects[j].y - objects[i].y; var du = objects[j].u - objects[i].u; var dv = objects[j].v - objects[i].v; var dr = objects[j].r + objects[i].r; var dt = (-Math.sqrt(2 * dx * du * dy * dv - du * du * (dy * dy - dr * dr) - dv * dv * (dx * dx - dr * dr)) - dx * du - dy * dv) / (du * du + dv * dv); Dx = objects[j].x - objects[i].x + dt * (objects[j].u - objects[i].u); Dy = objects[j].y - objects[i].y + dt * (objects[j].v - objects[i].v); D2 = Dx * Dx + Dy * Dy; var delta = 2 * (Dx * (objects[i].u - objects[j].u) + Dy * (objects[i].v - objects[j].v)) / (D2 * (objects[i].m + objects[j].m)); objects[i].u += -objects[i].m * delta * Dx; objects[i].v += -objects[i].m * delta * Dy; objects[j].u += objects[j].m * delta * Dx; objects[j].v += objects[j].m * delta * Dy; objects[i].x += (timeStep - dt) * objects[i].u; objects[i].y += (timeStep - dt) * objects[i].v; objects[j].x += (timeStep - dt) * objects[j].u; objects[j].y += (timeStep - dt) * objects[j].v; } } } } </code></pre>
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