Shapes::CCircle Class Reference

Circle shape. More...

#include <Circle.h>

Inheritance diagram for Shapes::CCircle:

Collaboration diagram for Shapes::CCircle:

Public Member Functions
	CCircle (const CCircleDesc &)
	Constructor.
const bool	CollisionDetected (CContactDesc &) const
	Collision detection.
const bool	PtInCircle (const Vector2 &) const
	Point in circle test.
const Vector2	ClosestPt (const Vector2 &) const
	Closest point on circle.
const bool	Tangents (const Vector2 &, Vector2 &, Vector2 &) const
	Tangents through external point.
const bool	Tangents (const CCircle *, CLineSegDesc &, CLineSegDesc &) const
	Common tangents.
const bool	Tangent (const CCircle *, CLineSegDesc &) const
	Common tangent.
const float	GetRadius () const
	Get radius.
Public Member Functions inherited from Shapes::CShape
	CShape (const CShapeDesc &)
	Constructor.
virtual	~CShape ()
	Destructor.
const eShape	GetShapeType () const
	Get shape type.
const eMotion	GetMotionType () const
	Get motion type.
const CAabb2D &	GetAABB () const
	Get AABB.
const bool	GetSensor () const
	Is this shape a sensor?
const Vector2 &	GetPos () const
	Get position.
void	SetPos (const Vector2 &)
	Set position.
void	SetAABBPoint (const Vector2 &)
	Set AABB point.
void	AddAABBPoint (const Vector2 &)
	Add AABB point.
void	SetCanCollide (bool=true)
	Turn collisions on or off.
const bool	GetCanCollide () const
	Get whether shape can collide.
const bool	GetRotating () const
	Get whether rotating.
void	SetRotating (bool)
	Start or stop rotating.
const float	GetOrientation () const
	Get orientation.
void	SetOrientation (float)
	Set orientation.
const float	GetRotSpeed () const
	Get rotation speed.
void	SetRotSpeed (float)
	Set rotation speed.
const Vector2 &	GetRotCenter () const
	Get rotation speed.
void	SetRotCenter (const Vector2 &)
	Set center of rotation.
const float	GetElasticity () const
	Get elasticity.
void *	GetUserPtr () const
	Get user pointer.
void	SetUserPtr (void *)
	Set user pointer.
virtual void	Rotate (const Vector2 &, float)
	Rotate.
virtual void	Reset ()
	Reset orientation.
virtual void	move ()
	Translate.

Protected Attributes
float	m_fRadius = 0.0f
	Radius.
float	m_fRadiusSq = 0.0f
	Radius squared, for fast distance calc.
Protected Attributes inherited from Shapes::CShape
eShape	m_eShapeType = eShape::Unknown
	Type of shape.
eMotion	m_eMotionType = eMotion::Static
	How shape moves.
float	m_fElasticity = 1.0f
	Elasticity, aka restitution, bounciness.
bool	m_bIsSensor = false
	Sensor only, no rebound on collision.
CAabb2D	m_cAABB
	Axially aligned bounding box in World Space.
bool	m_bCanCollide = true
	Can collide with other shapes.
float	m_fOrientation = 0.0f
	Orientation angle.
void *	m_pUser
	Spare pointer for user in case they might need one.
Vector2	m_vRotCenter
	Center of rotation.
float	m_fRotSpeed = 0.0f
	Rotation speed.
bool	m_bRotating = false
	Whether rotating.

Additional Inherited Members
Static Protected Attributes inherited from Shapes::CShapeCommon
static float	m_fGravity = 0.0f
	Gravitational constant.
static float	m_fTimeStep = 0.0f
	Time step per animation frame (fictional).

Detailed Description

A circle is represented by the position of its center and its radius.

Constructor & Destructor Documentation

CCircle()

CCircle::CCircle

(

const CCircleDesc &

r

)

Constructs a circle described by a circle descriptor.

Parameters

r	Circle descriptor.

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Member Function Documentation

ClosestPt()

const Vector2 CCircle::ClosestPt

(

const Vector2 &

p

)

const

Find the point on the perimeter that is closest to a given point.

Parameters

p

A point.

Returns

The closest point to p that is on the perimeter.

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CollisionDetected()

const bool CCircle::CollisionDetected ( CContactDesc & c ) const

virtual

Collision detection with a dynamic circle. This function kluges out by using the closest point on this circle to the center of the other circle as the POI, and then letting CPoint do the rest of the work.

Parameters

c	[in, out] Contact descriptor for this collision.

Returns

true is there was a collision.

Reimplemented from Shapes::CShape.

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GetRadius()

const float CCircle::GetRadius

(

)

const

Reader function for the radius.

Returns

The radius.

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PtInCircle()

const bool CCircle::PtInCircle

(

const Vector2 &

p

)

const

Determine whether a given point is strictly inside this circle, that is, if the point's distance to the center of this circle is strictly less that its radius.

Parameters

p

A point.

Returns

true if p is in this circle.

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Tangent()

const bool CCircle::Tangent	(	const CCircle *	pCirc,
		CLineSegDesc &	t ) const

Compute the common tangent with another circle that is counterclockwise from the vector pointing from this circle to that one.

Parameters

	pCirc	Pointer to another circle.
[out]	t	Line segment descriptor for common tangent.

Returns

true if tangent exists.

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Tangents() [1/2]

const bool CCircle::Tangents	(	const CCircle *	pCirc,
		CLineSegDesc &	t0,
		CLineSegDesc &	t1 ) const

A line tangent to circles at centers \(p_0\) and \(p_1\) of radii \(r_0\) and \(r_1 < r_0\) is constructed by constructing the tangent to a single circle of radius \(r_0 - r_1\) centered at \(p_0\) and through \(p_1\), then translating this line segment along the radius through \(p_0\) a distance \(r_1\). See J. Casey, "A sequel to the First Six Books of the Elements of Euclid", pp. 31-32, 1888.

Parameters

	pCirc	Pointer to another circle.
[out]	t0	Line segment descriptor for first common tangent.
[out]	t1	Line segment descriptor for second common tangent.

Returns

true if tangents exist.

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Tangents() [2/2]

const bool CCircle::Tangents	(	const Vector2 &	p,
		Vector2 &	p0,
		Vector2 &	p1 ) const

Compute the points of intersection of tangents passing through a point. Note that there are two possible tangents to a circle that pass through a given point outside the circle. If the point is inside the circle, then the tangents don't exist.

Parameters

	p	Point that must lie on the tangents.
[out]	p0	Intersection point with first tangent.
[out]	p1	Intersection point with second tangent.

Returns

true if the tangents exist.

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