G3D::Cylinder Class Reference

#include <Cylinder.h>

Public Member Functions
	Cylinder ()
	Cylinder (class BinaryInput &b)
	Cylinder (const Vector3 &_p1, const Vector3 &_p2, float _r)
void	serialize (class BinaryOutput &b) const
void	deserialize (class BinaryInput &b)
Line	axis () const
void	getReferenceFrame (class CoordinateFrame &cframe) const
const Vector3 &	point (int i) const
bool	contains (const Vector3 &p) const
float	area () const
float	volume () const
float	radius () const
Vector3	center () const
float	height () const
void	getBounds (AABox &out) const
void	getRandomSurfacePoint (Vector3 &P, Vector3 &N) const
Vector3	randomInteriorPoint () const

Private Attributes
Vector3	p1
Vector3	p2
float	mRadius

Detailed Description

Right cylinder

Constructor & Destructor Documentation

G3D::Cylinder::Cylinder

(

)

Uninitialized

 {
}

G3D::Cylinder::Cylinder

(

class BinaryInput &

b

)

 {
 deserialize(b);
}

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G3D::Cylinder::Cylinder	(	const Vector3 &	_p1,
		const Vector3 &	_p2,
		float	_r
	)

 : p1(_p1), p2(_p2), mRadius(_r) {
}

Member Function Documentation

float G3D::Cylinder::area

(

)

const

 {
 return
 // Sides
 ((float)twoPi() * mRadius) * height() +

 // Caps
 (float)twoPi() * square(mRadius);
}

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Line G3D::Cylinder::axis

(

)

const

The line down the center of the Cylinder

 {
 return Line::fromTwoPoints(p1, p2);
}

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Vector3 G3D::Cylinder::center ( ) const

inline

Center of mass

 {
 return (p1 + p2) / 2.0f;
 }

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bool G3D::Cylinder::contains

(

const Vector3 &

p

)

const

Returns true if the point is inside the Cylinder or on its surface.

 { 
 return LineSegment::fromTwoPoints(p1, p2).distanceSquared(p) <= square(mRadius);
}

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void G3D::Cylinder::deserialize

(

class BinaryInput &

b

)

 {
 p1.deserialize(b);
 p2.deserialize(b);
 mRadius = (float)b.readFloat64();
}

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void G3D::Cylinder::getBounds

(

AABox &

out

)

const

Get close axis aligned bounding box. With vertical world orientation, the top and bottom might not be very tight.

 {
 Vector3 min = p1.min(p2) - (Vector3(1, 1, 1) * mRadius);
 Vector3 max = p1.max(p2) + (Vector3(1, 1, 1) * mRadius);
 out = AABox(min, max);
}

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void G3D::Cylinder::getRandomSurfacePoint	(	Vector3 &	P,
		Vector3 &	N
	)		const

Random world space point with outward facing normal.

 {
 float h = height();
 float r = radius();

 // Create a random point on a standard cylinder and then rotate to the global frame.

 // Relative areas (factor of 2PI already taken out)
 float capRelArea = square(r) / 2.0f;
 float sideRelArea = r * h;

 float r1 = uniformRandom(0, capRelArea * 2 + sideRelArea);

 if (r1 < capRelArea * 2) {

 // Select a point uniformly at random on a disk
 // @cite http://mathworld.wolfram.com/DiskPointPicking.html
 float a = uniformRandom(0, (float)twoPi());
 float r2 = sqrt(uniformRandom(0, 1)) * r;
 p.x = cos(a) * r2;
 p.z = sin(a) * r2;

 N.x = 0;
 N.z = 0;
 if (r1 < capRelArea) {
 // Top
 p.y = h / 2.0f;
 N.y = 1;
 } else {
 // Bottom
 p.y = -h / 2.0f;
 N.y = -1;
 }
 } else {
 // Side
 float a = uniformRandom(0, (float)twoPi());
 N.x = cos(a);
 N.y = 0;
 N.z = sin(a);
 p.x = N.x * r;
 p.z = N.y * r;
 p.y = uniformRandom(-h / 2.0f, h / 2.0f);
 }

 // Transform to world space
 CoordinateFrame cframe;
 getReferenceFrame(cframe);
 
 p = cframe.pointToWorldSpace(p);
 N = cframe.normalToWorldSpace(N);
}

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void G3D::Cylinder::getReferenceFrame

(

class CoordinateFrame &

cframe

)

const

A reference frame in which the center of mass is at the origin and the Y-axis is the cylinder's axis. If the cylinder is transformed, this reference frame may freely rotate around its axis.

 {
 cframe.translation = center();

 Vector3 Y = (p1 - p2).direction();
 Vector3 X = (abs(Y.dot(Vector3::unitX())) > 0.9) ? Vector3::unitY() : Vector3::unitX();
 Vector3 Z = X.cross(Y).direction();
 X = Y.cross(Z); 
 cframe.rotation.setColumn(0, X);
 cframe.rotation.setColumn(1, Y);
 cframe.rotation.setColumn(2, Z);
}

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float G3D::Cylinder::height ( ) const

inline

 {
 return (p1 - p2).magnitude();
 }

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const Vector3& G3D::Cylinder::point ( int  i ) const

inline

Returns point 0 or 1

 {
 debugAssert(i >= 0 && i <= 1);
 return (i == 0) ? p1 : p2;
 }

float G3D::Cylinder::radius

(

)

const

 {
 return mRadius;
}

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Vector3 G3D::Cylinder::randomInteriorPoint

(

)

const

Point selected uniformly at random over the volume.

 {
 float h = height();
 float r = radius();

 // Create a random point in a standard cylinder and then rotate to the global frame.

 // Select a point uniformly at random on a disk
 // @cite http://mathworld.wolfram.com/DiskPointPicking.html
 float a = uniformRandom(0, (float)twoPi());
 float r2 = sqrt(uniformRandom(0, 1)) * r;

 Vector3 p( cos(a) * r2,
 uniformRandom(-h / 2.0f, h / 2.0f),
 sin(a) * r2);

 // Transform to world space
 CoordinateFrame cframe;
 getReferenceFrame(cframe);
 
 return cframe.pointToWorldSpace(p);
}

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void G3D::Cylinder::serialize

(

class BinaryOutput &

b

)

const

 {
 p1.serialize(b);
 p2.serialize(b);
 b.writeFloat64(mRadius);
}

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float G3D::Cylinder::volume

(

)

const

 {
 return
 (float)pi() * square(mRadius) * (p1 - p2).magnitude();
}

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Member Data Documentation

float G3D::Cylinder::mRadius

private

Vector3 G3D::Cylinder::p1

private

Vector3 G3D::Cylinder::p2

private

---

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

• dep/g3dlite/include/G3D/Cylinder.h
• dep/g3dlite/source/Cylinder.cpp