5-adding_general_force

D’ALEMBERT’S PRINCIPLE

For particles D’Alembert’s principle implies that, if we have a set of forces acting on an object, we can replace all those forces with a single force, which is calculated by

\[f = \sum\limits_{i} f_{i} \]

In other words, we simply add the forces together using vector addition, and we apply the single force that results.

FORCE GENERATORS

class ParticleForceGenerator
{
public:
    /**
    * Overload this in implementations of the interface to calculate
    * and update the force applied to the given particle.
    */
    virtual void updateForce(Particle *particle, real duration) = 0; //更新每个粒子的加速度
};

A GRAVITY FORCE GENERATOR

class ParticleGravity : public ParticleForceGenerator
{
    /** Holds the acceleration due to gravity. */
    Vector3 gravity;
    public:
    /** Creates the generator with the given acceleration. */
    ParticleGravity(const Vector3 &gravity);
    /** Applies the gravitational force to the given particle. */
    virtual void updateForce(Particle *particle, real duration);
};