G3D::Cone Class Reference

#include <Cone.h>

Public Member Functions
	Cone (const Vector3 &tip, const Vector3 &direction, float angle)
	Cone (const Vector3 &tip, const class Box &box)
virtual	~Cone ()
bool	intersects (const class Sphere &s) const
bool	contains (const class Vector3 &v) const
Vector3	randomDirectionInCone (Random &rng) const

Static Public Member Functions
static float	solidAngleFromHalfAngle (float halfAngle)
static double	solidAngleFromHalfAngle (double halfAngle)
static float	halfAngleFromSolidAngle (float solidAngle)
static double	halfAngleFromSolidAngle (double solidAngle)

Private Attributes
Vector3	tip
Vector3	direction
float	angle

Detailed Description

An infinite cone.

Constructor & Destructor Documentation

G3D::Cone::Cone	(	const Vector3 &	tip,
		const Vector3 &	direction,
		float	angle
	)

Parameters

angle

Angle from the center line to the edge, in radians

 {
 this->tip = tip;
 this->direction = direction.direction();
 this->angle = angle;

 debugAssert(angle >= 0);
 debugAssert(angle <= pi());
}

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G3D::Cone::Cone	(	const Vector3 &	tip,
		const class Box &	box
	)

Forms the smallest cone that contains the box. Undefined if the tip is inside or on the box.

virtual G3D::Cone::~Cone ( )

inlinevirtual

{}

Member Function Documentation

bool G3D::Cone::contains

(

const class Vector3 &

v

)

const

True if v is a point inside the cone.

 {

 Vector3 d = (v - tip).direction();

 float x = d.dot(direction);

 return (x > 0) && (x >= cosf(angle));
}

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float G3D::Cone::halfAngleFromSolidAngle ( float  solidAngle )

static

Returns the half-angle (in radians) of a cone that subtends solidAngle (in steradians)

 {
 return acos((1.0f - (solidAngle / (2.0f * pif()))));
}

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double G3D::Cone::halfAngleFromSolidAngle ( double  solidAngle )

static

 {
 return aCos((1.0 - (solidAngle / (2.0 * pi()))));
}

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bool G3D::Cone::intersects

(

const class Sphere &

s

)

const

Returns true if the cone touches, intersects, or contains b.

If c.intersects(s) and c.intersects(Sphere(s.center, s.radius * 2) then the sphere s is entirely within cone c.

 {
 // If the bounding sphere contains the tip, then
 // they definitely touch.
 if (b.contains(this->tip)) {
 return true;
 }

 // Move the tip backwards, effectively making the cone bigger
 // to account for the radius of the sphere.

 Vector3 tip = this->tip - direction * b.radius / sinf(angle);

 return Cone(tip, direction, angle).contains(b.center);
}

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Vector3 G3D::Cone::randomDirectionInCone

(

Random &

rng

)

const

 {
 const float cosThresh = cos(angle);

 float cosAngle;
 float normalizer;
 Vector3 v;
 do {
 float vlenSquared;

 // Sample uniformly on a sphere by rejection sampling and then normalizing
 do {
 v.x = rng.uniform(-1, 1);
 v.y = rng.uniform(-1, 1);
 v.z = rng.uniform(-1, 1);

 // Sample uniformly on a cube
 vlenSquared = v.squaredLength();
 } while (vlenSquared > 1);


 const float temp = v.dot(direction);
 
 // Compute 1 / ||v||, but
 // if the vector is in the wrong hemisphere, flip the sign
 normalizer = rsqrt(vlenSquared) * sign(temp);

 // Cosine of the angle between v and the light's negative-z axis
 cosAngle = temp * normalizer;

 } while (cosAngle < cosThresh);

 // v was within the cone. Normalize it and maybe flip the hemisphere.
 return v * normalizer;
 }

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float G3D::Cone::solidAngleFromHalfAngle ( float  halfAngle )

static

Returns the solid angle (in steradians) subtended by a cone with half-angle halfAngle

 {
 return 2.0f * pif() * (1 - cosf(halfAngle));
}

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double G3D::Cone::solidAngleFromHalfAngle ( double  halfAngle )

static

 {
 return 2.0 * pi() * (1.0 - cos(halfAngle));
}

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Member Data Documentation

float G3D::Cone::angle

private

Angle from the center line to the edge.

Vector3 G3D::Cone::direction

private

Vector3 G3D::Cone::tip

private

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

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