d2arrow Class Reference

Arrow in 2D to aid in visualization. More...

#include <d2arrow.h>

Inheritance diagram for d2arrow:

Collaboration diagram for d2arrow:

List of all members.

Public Member Functions
	d2arrow (doublec arrowlength, doublec headlength)
	Construct an arrow along the x-axis.
	d2arrow (point2< double > const &pi0, doublec theta, doublec arrowlength, doublec headlength)
	Construct an arrow at the point and rotate it.
	d2arrow (point2< double > const &q0, point2< double > const &q1, doublec arrowlength, doublec headlength)
	Construct a normal.
void	draw ()
	Draw the arrow.
void	rotate (doublec theta)
	Rotate the arrow about pi[0] by theta radians.
void	translate (point2< double > const &x)
	Shift the arrow by x.
void	constructOnXaxis (doublec arrowlength, doublec headlength)
	Construct an arrow along the x-axis.
Public Attributes
point2< double >	pi [4]
	Arrow geometry.
Static Public Attributes
static double	headlengthfactor = 0.8
	Change how fat or thin the arrow head is.

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Detailed Description

Arrow in 2D to aid in visualization.

The arrow can be constructed in several ways. The simplest is along the x-axis where I would then use OpenGL to do the transformations. A normal can be constructed given two points which is really useful. The standard generic position and angle is there too.

The arrows geometric points are public so if the client wishes to use this class efficiently they should directly apply any transforms to the points and call draw() rather than using this classes transformations.

Arrow point geometry for pi[].

2 \ \ 0 -------------------- 1 / / 3 arrowlength = distance(0,1) headlength = the distance from 1 to intersecting line (2,3) head height = distance(2,3)

Definition at line 36 of file d2arrow.h.

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Constructor & Destructor Documentation

d2arrow::d2arrow	(	doublec	arrowlength,
		doublec	headlength
	)

Construct an arrow along the x-axis.

Definition at line 30 of file d2arrow.cpp.

{
  constructOnXaxis(arrowlength,headlength);
}

d2arrow::d2arrow	(	point2< double > const &	pi0,
		doublec	theta,
		doublec	arrowlength,
		doublec	headlength
	)

Construct an arrow at the point and rotate it.

Definition at line 39 of file d2arrow.cpp.

{
  constructOnXaxis(arrowlength,headlength);
  translate(pi0);
  rotate(theta);
}

d2arrow::d2arrow	(	point2< double > const &	q0,
		point2< double > const &	q1,
		doublec	arrowlength,
		doublec	headlength
	)

Construct a normal.

The arrow is rotated 90 degrees to line (q0,q1) with the base of the arrow in between q0 and q1.

Definition at line 52 of file d2arrow.cpp.

References point2< T >::normalize(), point2< T >::x, and point2< T >::y.

{
  // Using vector calculus to calculate the arrows
  // geometry points.

  // Construct unit vectors z1 and z2 where z2 is the normal.
  // Further z1 = z2 rotated 90 degrees anticlockwise direction.

  // z1 and z2 are at right angles and form a coordinate system.

  point2<double> z1(q1-q0);
  z1.normalize();
  point2<double> z2(-z1.y,z1.x);

  // The head base of the arrow.
  point2<double> hb(z2);
  hb *= (arrowlength-headlength);

  // Half the hight of the arrow head.
  double w = headlength*headlengthfactor*0.5;

  pi[2] = hb - z1 * w;
  pi[3] = hb + z1 * w;
  pi[1] = z2*arrowlength;
  pi[0] = point2<double>(0.0,0.0);

  point2<double> p0(q0+q1);
  p0 *= 0.5;
  translate(p0);
}

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Member Function Documentation

void d2arrow::constructOnXaxis	(	doublec	arrowlength,
		doublec	headlength
	)

Construct an arrow along the x-axis.

Definition at line 90 of file d2arrow.cpp.

{
  assert(arrowlength>headlength);
  assert(arrowlength>0.0);

  pi[0] = point2<double>(0.0,0.0);
  pi[1] = point2<double>(arrowlength,0.0);
  doublec q = arrowlength-headlength;
  doublec arrowheight = headlength*headlengthfactor*0.5;
  pi[2] = point2<double>(q,arrowheight);
  pi[3] = point2<double>(q,-arrowheight);
}

void d2arrow::draw

(

)

[virtual]

Draw the arrow.

Implements gobj.

Definition at line 106 of file d2arrow.cpp.

References pi.

Referenced by d2simplexNormals::draw().

{
  glBegin(GL_LINES);

  glVertex3f(pi[0].x,pi[0].y,0.0);
  glVertex3f(pi[1].x,pi[1].y,0.0);

  glEnd();

  glBegin(GL_TRIANGLES);

  glVertex3f(pi[1].x,pi[1].y,0.0);
  glVertex3f(pi[2].x,pi[2].y,0.0);
  glVertex3f(pi[3].x,pi[3].y,0.0);

  glEnd();
}

void d2arrow::rotate

(

doublec

theta

)

Rotate the arrow about pi[0] by theta radians.

Definition at line 19 of file d2arrow.cpp.

References d2homogeneous::matrixMultiply(), pi, and d2homogeneous::setRotateAboutPoint().

{
  d2homogeneous R;

  R.setRotateAboutPoint(theta,pi[0]);

  for (uint i=1; i<4; ++i)
    R.matrixMultiply(pi[i]);
}

void d2arrow::translate

(

point2< double > const &

x

)

Shift the arrow by x.

Definition at line 13 of file d2arrow.cpp.

References pi.

{
  for (uint i=0; i<4; ++i)
    pi[i] += x; 
}

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Member Data Documentation

double d2arrow::headlengthfactor = 0.8 [static]

Change how fat or thin the arrow head is.

This multiplied by the headlength gives the height of the arrow head.

Definition at line 45 of file d2arrow.h.

point2<double> d2arrow::pi[4]

Arrow geometry.

Definition at line 41 of file d2arrow.h.

Referenced by draw(), rotate(), and translate().

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

• intersectiontests/d2arrow.h
• intersectiontests/d2arrow.cpp