LocalCoordinatesSite Class Reference

This is a VirtualSite that uses the locations of three other particles to compute a local coordinate system, then places the virtual site at a fixed location in that coordinate system. More...

#include <VirtualSite.h>

Inheritance diagram for LocalCoordinatesSite:

Public Member Functions
	LocalCoordinatesSite (int particle1, int particle2, int particle3, const Vec3 &originWeights, const Vec3 &xWeights, const Vec3 &yWeights, const Vec3 &localPosition)
	Create a new LocalCoordinatesSite virtual site. More...
const Vec3 &	getOriginWeights () const
	Get the weight factors for the three particles when computing the origin location. More...
const Vec3 &	getXWeights () const
	Get the weight factors for the three particles when computing xdir. More...
const Vec3 &	getYWeights () const
	Get the weight factors for the three particles when computing ydir. More...
const Vec3 &	getLocalPosition () const
	Get the position of the virtual site in the local coordinate system. More...
Public Member Functions inherited from VirtualSite
virtual	~VirtualSite ()
int	getNumParticles () const
	Get the number of particles this virtual site depends on. More...
int	getParticle (int particle) const
	Get the index of a particle this virtual site depends on. More...

Additional Inherited Members
Protected Member Functions inherited from VirtualSite
	VirtualSite ()
void	setParticles (const std::vector< int > &particleIndices)

Detailed Description

This is a VirtualSite that uses the locations of three other particles to compute a local coordinate system, then places the virtual site at a fixed location in that coordinate system.

The origin of the coordinate system and the directions of its x and y axes are each specified as a weighted sum of the locations of the three particles:

origin = w^o₁r₁ + w^o₂r₂ + w^o₃r₃

xdir = w^x₁r₁ + w^x₂r₂ + w^x₃r₃

ydir = w^y₁r₁ + w^y₂r₂ + w^y₃r₃

For the origin, the three weights must add to one. For example if (w^o₁, w^o₂, w^o₃) = (1.0, 0.0, 0.0), the origin of the local coordinate system is at the location of particle 1. For xdir and ydir, the weights must add to zero. For excample, if (w^x₁, w^x₂, w^x₃) = (-1.0, 0.5, 0.5), the x axis points from particle 1 toward the midpoint between particles 2 and 3.

The z direction is computed as zdir = xdir x ydir. To ensure the axes are all orthogonal, ydir is then recomputed as ydir = zdir x xdir. All three axis vectors are then normalized, and the virtual site location is set to

origin + x*xdir + y*ydir + z*zdir

Constructor & Destructor Documentation

LocalCoordinatesSite	(	int	particle1,
		int	particle2,
		int	particle3,
		const Vec3 &	originWeights,
		const Vec3 &	xWeights,
		const Vec3 &	yWeights,
		const Vec3 &	localPosition
	)

Create a new LocalCoordinatesSite virtual site.

Parameters

particle1	the index of the first particle
particle2	the index of the second particle
particle3	the index of the third particle
originWeights	the weight factors for the three particles when computing the origin location
xWeights	the weight factors for the three particles when computing xdir
yWeights	the weight factors for the three particles when computing ydir
localPosition	the position of the virtual site in the local coordinate system

Member Function Documentation

const Vec3& getLocalPosition

(

)

const

Get the position of the virtual site in the local coordinate system.

const Vec3& getOriginWeights

(

)

const

Get the weight factors for the three particles when computing the origin location.

const Vec3& getXWeights

(

)

const

Get the weight factors for the three particles when computing xdir.

const Vec3& getYWeights

(

)

const

Get the weight factors for the three particles when computing ydir.

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The documentation for this class was generated from the following file:

• VirtualSite.h