DiscSystem Class Reference

A particle system constrained to an implicit surface. More...

#include <discsystem.h>

Public Member Functions
	DiscSystem (const AnalyticScalarField *, const double &, int)
	Creates a particle system constrained to an implicit surface.
	~DiscSystem ()
	Destroy a particle system.
void	Steps (int=1)
	Update the particle system.
void	Cast ()
	Cast all the particles on the implicit surface.
Circle	operator() (int) const
	Get the i-th particle.
Circle &	operator() (int)
	Get the i-th particle.
void	AddParticle (const Vector &, const double &)
	Insert a new particle in the list.
int	Size () const
	Get the number of particles.

Protected Member Functions
void	Cast (int)
	Cast a particle on the implicit surface.
void	Step (int)
	Particle update.
int	Closest (int, int *, double *) const
	Find the neighbors closest to a particle.
void	Compute (int, Vector &, double &, bool &, bool &, int, int *)
	Computes the position and radius derivatives with respect to time.
void	SplitParticle (int)
	Split a particle into two slighly perturbed ones.
void	DeleteParticle (int)
	Delete a particle.

Protected Attributes
DynamicArrayIndex	subd
	Voxel subdivision of space required for an efficient determination of neighbor relations between particles.
QVector< Circle >	particles
	Array of particles.
double	time_step = 1.0
	Step size for numerical integration.
const AnalyticScalarField *	function = nullptr
	Reference to function.
double	ir = 1.0
	Initial radius.

Static Protected Attributes
static const double	Beta = 10.0
	Used in computation of the variation of radius.
static const double	Gamma = 4.0
	Equilibrium speed.
static const double	Delta = 0.7
	Percentage of nominal radius, used as minimum radius.
static const double	Rho = 10.0
	Coefficient for radius term.
static const double	WH_PHI = 10.0
	For gradient feedback term.
static const double	DeltaT = 0.1
	Time step.
static const double	sigma = 1.5
	Coefficient for splitting particles.
static const double	epsilon = 0.001
	Gradient epsilon for vanishing gradient.

Detailed Description

A particle system constrained to an implicit surface.

This class implements Witkin-Heckbert particle system over an implicit surface. It may be used to generate a cloud of vertices located almost uniformly over the implicit surface.

Constructor & Destructor Documentation

DiscSystem()

DiscSystem::DiscSystem	(	const AnalyticScalarField *	f,
		const double &	r,
		int	n )

Creates a particle system constrained to an implicit surface.

Parameters

f	Implicit surface class.
r	Radius of the particles.
n	Spatial subdivision used to speed up particle update.

~DiscSystem()

DiscSystem::~DiscSystem

(

)

Destroy a particle system.

This function destroys the internal acceleration data-structures but does not destroy the implicit function.

Member Function Documentation

AddParticle()

void DiscSystem::AddParticle	(	const Vector &	p,
		const double &	r )

Insert a new particle in the list.

This function hides the particles-poll mechanism that keeps track of indices of previously deleted indices to be reused. The gradient of the field function at the location of the particle is computed internally.

Parameters

p	Center of new particle.
r	Radius of particle.

Cast()

void DiscSystem::Cast ( int i )

protected

Cast a particle on the implicit surface.

The particle is destroyed if gradient vanishes to null.

Parameters

i	Particle identifier.

Closest()

int DiscSystem::Closest ( int id, int * cc, double * ll ) const

protected

Find the neighbors closest to a particle.

These are saved in a cache to improve speed in calculations of repulsion forces.

Compute()

void DiscSystem::Compute ( int id, Vector & delta_P, double & delta_rad, bool & split_flag, bool & death_flag, int ncl, int * close )

protected

Computes the position and radius derivatives with respect to time.

Parameters

id	Index of particle (should be called with ci[k] as argument).
delta_P	Variation of the position of the particle (projected to tangent plane).
delta_rad	Variation of the radius of the particle.
split_flag	Splitting flag.
death_flag	Death flag.
ncl	Number of closest particles.
close	Id of closest particles.

DeleteParticle()

void DiscSystem::DeleteParticle ( int id )

protected

Delete a particle.

Parameters

id

Index.

SplitParticle()

void DiscSystem::SplitParticle ( int i )

protected

Split a particle into two slighly perturbed ones.

Parameters

i	Index of particle.

Step()

void DiscSystem::Step ( int i )

protected

Particle update.

Find the closest neighbors, and then computes Witkin and Hekbert parameters. Particle's behavior is modified according to those parameters.

Parameters

i	Index of particle.

Steps()

void DiscSystem::Steps

(

int

n = 1

)

Update the particle system.

Iteratively update all particles.

Parameters

n	Number of iterations.