chris@164: /*
chris@164:  *
chris@164:  * Simple 1-Dimensional Mass Spring Damper
chris@164:  *
chris@164:  * Christian Heinrichs 04/2015
chris@164:  *
chris@164:  */
chris@164: 
chris@164: #include "MassSpringDamper.h"
chris@164: 
chris@164: MassSpringDamper::MassSpringDamper(float mass, float spring, float damp)	{
chris@164: 
chris@164: 	_dt = 1.0/44100.0;
chris@164: 	_mass = mass;
chris@164: 	_spring = spring;
chris@164: 	_damp = damp;
chris@164: 	_position = 0;
chris@164: 	_velocity = 0;
chris@164: 
chris@164: }
chris@164: 
chris@164: void MassSpringDamper::setup()	{
chris@164: 
chris@164: }
chris@164: 
chris@164: double MassSpringDamper::update(float inForce)	{
chris@164: 
chris@164: 	// 1. calculate spring/damper forces using current position and velocity
chris@164: 
chris@164: 	double out = (_position * (double)_spring * -1) + (_velocity * (double)_damp * -1);
chris@164: 
chris@164: 	// 2. apply external force
chris@164: 
chris@164: 	out += inForce;
chris@164: 
chris@164: 	// 3. derive acceleration (a = f/m)
chris@164: 
chris@164: 	out /= (double)_mass;
chris@164: 
chris@164: 	// 4. derive velocity (v = a*dt)
chris@164: 
chris@164: 	out *= _dt;
chris@164: 
chris@164: 	// 5. apply previous velocity
chris@164: 
chris@164: 	out += _velocity;
chris@164: 
chris@164: 	// 6. save current velocity state for next iteration
chris@164: 
chris@164: 	_velocity = out;
chris@164: 
chris@164: 	// 7. derive new position (x[n] = x[n-1] + v[n]) and save for next iteration
chris@164: 
chris@164: 	out += _position;
chris@164: 	_position = out;
chris@164: 
chris@164: 	return out;
chris@164: 
chris@164: }