53 lines
1.6 KiB
JavaScript
53 lines
1.6 KiB
JavaScript
function move_particles(particles, force_constant) {
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for (let particle of particles) {
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particle.acceleration.setMag(0);
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}
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for (let i = 0; i < particles.length; i += 1) {
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for (let j = 0; j < i; j += 1) {
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const displacement = p5.Vector.sub(
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particles[i].position,
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particles[j].position,
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);
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const force_mag = (
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particles[i].charge * particles[j].charge
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/ displacement.magSq()
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* force_constant
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);
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// XXX possible extension: divide by charge's mass
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const ai_mag = force_mag;
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const aj_mag = force_mag;
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let ai;
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let aj;
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if (force_mag === Infinity) {
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ai = p5.Vector.random3D();
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aj = p5.Vector.random3D();
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} else {
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ai = displacement.copy().normalize();
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aj = ai.copy().mult(-1);
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}
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ai.mult(ai_mag);
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aj.mult(aj_mag);
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project_onto_plane(ai, particles[i].position);
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project_onto_plane(aj, particles[j].position);
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particles[i].acceleration.add(ai);
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particles[j].acceleration.add(aj);
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}
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}
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for (let particle of particles) {
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particle.velocity = particle.velocity.add(particle.acceleration);
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particle.position = particle.position.add(particle.velocity);
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particle.position.normalize();
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}
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}
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function project_onto_unit_vector(v, unit_vector) {
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let size = p5.Vector.dot(v, unit_vector);
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return p5.Vector.mult(unit_vector, size);
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}
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/// Project `v` onto the plane normal to `unit_vector`
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/// Mutates `v`
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function project_onto_plane(v, unit_vector) {
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let v_proj = project_onto_unit_vector(v, unit_vector);
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v.sub(v_proj)
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}
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