94 lines
1.9 KiB
C++
94 lines
1.9 KiB
C++
// -*- C++ -*-
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#include <stdio.h>
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#include <stdlib.h>
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#include "force.h"
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#include "particle.h"
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#include "vector.h"
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using namespace mbostock;
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static const float epsilon = 1E-20;
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void UnaryForce::apply(Particle& p) {
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p.force += force(p);
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}
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void BinaryForce::apply(Particle& a, Particle& b) {
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Vector f = force(a, b);
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a.force += f;
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b.force -= f;
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}
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RandomForce::RandomForce(float k)
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: k_(k) {
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}
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Vector RandomForce::force(Particle& p) {
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return Vector::randomVector(k_);
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}
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GravitationalForce::GravitationalForce(float g)
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: g_(g) {
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}
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Vector GravitationalForce::force(const Particle& p) {
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return Vector(0, -g_ / p.inverseMass, 0);
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}
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LinearDragForce::LinearDragForce(float kd)
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: kd_(kd) {
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}
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Vector LinearDragForce::force(const Particle& p) {
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return p.velocity() * -kd_;
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}
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QuadraticDragForce::QuadraticDragForce(float kd)
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: kd_(kd) {
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}
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Vector QuadraticDragForce::force(const Particle& p) {
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const Vector& v = p.velocity();
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return v * v.length() * -kd_;
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}
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HookeForce::HookeForce(float r, float ks)
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: r_(r), ks_(ks) {
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}
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Vector HookeForce::force(const Particle& a, const Particle& b) {
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Vector l = a.position - b.position;
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float ll = l.length();
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if (ll == 0.f) {
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l = Vector::randomVector(epsilon);
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ll = epsilon;
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}
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return l * -ks_ * (ll - r_) / ll;
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}
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DampenedHookeForce::DampenedHookeForce(float r, float ks, float kd)
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: r_(r), ks_(ks), kd_(kd) {
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}
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Vector DampenedHookeForce::force(const Particle& a, const Particle& b) {
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Vector l = a.position - b.position;
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Vector dl = a.velocity() - b.velocity();
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float ll = l.length();
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if (ll == 0.f) {
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l = Vector::randomVector(epsilon);
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ll = epsilon;
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}
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return l * -(ks_ * (ll - r_) + kd_ * dl.dot(l) / ll) / ll;
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}
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CoulombForce::CoulombForce(float e)
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: e_(e) {
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}
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Vector CoulombForce::force(const Particle& a, const Particle& b) {
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Vector l = a.position - b.position;
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float ll = l.length();
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return -l * e_ / (ll * ll * ll);
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}
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