SFML - Simple and Fast Multimedia Library

SFML

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Transformable

Decomposed transform defined by a position, a rotation and a scale. More...

#include <Transformable.hpp>

Inheritance diagram for sf::Transformable:

Public Member Functions
	Transformable ()
	Default constructor. More...

virtual	~Transformable ()
	Virtual destructor. More...

void	setPosition (float x, float y)
	set the position of the object More...

void	setPosition (const Vector2f &position)
	set the position of the object More...

void	setRotation (float angle)
	set the orientation of the object More...

void	setScale (float factorX, float factorY)
	set the scale factors of the object More...

void	setScale (const Vector2f &factors)
	set the scale factors of the object More...

void	setOrigin (float x, float y)
	set the local origin of the object More...

void	setOrigin (const Vector2f &origin)
	set the local origin of the object More...

const Vector2f &	getPosition () const
	get the position of the object More...

float	getRotation () const
	get the orientation of the object More...

const Vector2f &	getScale () const
	get the current scale of the object More...

const Vector2f &	getOrigin () const
	get the local origin of the object More...

void	move (float offsetX, float offsetY)
	Move the object by a given offset. More...

void	move (const Vector2f &offset)
	Move the object by a given offset. More...

void	rotate (float angle)
	Rotate the object. More...

void	scale (float factorX, float factorY)
	Scale the object. More...

void	scale (const Vector2f &factor)
	Scale the object. More...

const Transform &	getTransform () const
	get the combined transform of the object More...

const Transform &	getInverseTransform () const
	get the inverse of the combined transform of the object More...

Detailed Description

Decomposed transform defined by a position, a rotation and a scale.

This class is provided for convenience, on top of sf::Transform.

sf::Transform, as a low-level class, offers a great level of flexibility but it is not always convenient to manage. Indeed, one can easily combine any kind of operation, such as a translation followed by a rotation followed by a scaling, but once the result transform is built, there's no way to go backward and, let's say, change only the rotation without modifying the translation and scaling. The entire transform must be recomputed, which means that you need to retrieve the initial translation and scale factors as well, and combine them the same way you did before updating the rotation. This is a tedious operation, and it requires to store all the individual components of the final transform.

That's exactly what sf::Transformable was written for: it hides these variables and the composed transform behind an easy to use interface. You can set or get any of the individual components without worrying about the others. It also provides the composed transform (as a sf::Transform), and keeps it up-to-date.

In addition to the position, rotation and scale, sf::Transformable provides an "origin" component, which represents the local origin of the three other components. Let's take an example with a 10x10 pixels sprite. By default, the sprite is positioned/rotated/scaled relatively to its top-left corner, because it is the local point (0, 0). But if we change the origin to be (5, 5), the sprite will be positioned/rotated/scaled around its center instead. And if we set the origin to (10, 10), it will be transformed around its bottom-right corner.

To keep the sf::Transformable class simple, there's only one origin for all the components. You cannot position the sprite relatively to its top-left corner while rotating it around its center, for example. To do such things, use sf::Transform directly.

sf::Transformable can be used as a base class. It is often combined with sf::Drawable – that's what SFML's sprites, texts and shapes do.

class MyEntity : public sf::Transformable, public sf::Drawable
{
 virtual void draw(sf::RenderTarget& target, sf::RenderStates states) const
 {
        states.transform *= getTransform();
        target.draw(..., states);
    }
};
MyEntity entity;
entity.setPosition(10, 20);
entity.setRotation(45);
window.draw(entity);

It can also be used as a member, if you don't want to use its API directly (because you don't need all its functions, or you have different naming conventions for example).

class MyEntity
{
public:
 void SetPosition(const MyVector& v)
    {
        myTransform.setPosition(v.x(), v.y());
    }
 void Draw(sf::RenderTarget& target) const
 {
        target.draw(..., myTransform.getTransform());
    }
private:
 sf::Transformable myTransform;
};

A note on coordinates and undistorted rendering:
By default, SFML (or more exactly, OpenGL) may interpolate drawable objects such as sprites or texts when rendering. While this allows transitions like slow movements or rotations to appear smoothly, it can lead to unwanted results in some cases, for example blurred or distorted objects. In order to render a sf::Drawable object pixel-perfectly, make sure the involved coordinates allow a 1:1 mapping of pixels in the window to texels (pixels in the texture). More specifically, this means:

The object's position, origin and scale have no fractional part
The object's and the view's rotation are a multiple of 90 degrees
The view's center and size have no fractional part

See also: sf::Transform

Definition at line 41 of file Transformable.hpp.

Constructor & Destructor Documentation

sf::Transformable::Transformable ( )

Default constructor.

virtual sf::Transformable::~Transformable ( )

virtual

Virtual destructor.

Member Function Documentation

const Transform& sf::Transformable::getInverseTransform ( ) const

get the inverse of the combined transform of the object

Returns: Inverse of the combined transformations applied to the object

See also: getTransform

const Vector2f& sf::Transformable::getOrigin ( ) const

get the local origin of the object

Returns: Current origin

See also: setOrigin

const Vector2f& sf::Transformable::getPosition ( ) const

get the position of the object

Returns: Current position

See also: setPosition

float sf::Transformable::getRotation ( ) const

get the orientation of the object

The rotation is always in the range [0, 360].

Returns: Current rotation, in degrees

See also: setRotation

const Vector2f& sf::Transformable::getScale ( ) const

get the current scale of the object

Returns: Current scale factors

See also: setScale

const Transform& sf::Transformable::getTransform ( ) const

get the combined transform of the object

Returns: Transform combining the position/rotation/scale/origin of the object

See also: getInverseTransform

void sf::Transformable::move	(	float	offsetX,
		float	offsetY
	)

Move the object by a given offset.

This function adds to the current position of the object, unlike setPosition which overwrites it. Thus, it is equivalent to the following code:

sf::Vector2f pos = object.getPosition();

object.setPosition(pos.x + offsetX, pos.y + offsetY);

Parameters

offsetX	X offset
offsetY	Y offset

See also: setPosition

void sf::Transformable::move ( const Vector2f & offset )

Move the object by a given offset.

This function adds to the current position of the object, unlike setPosition which overwrites it. Thus, it is equivalent to the following code:

object.setPosition(object.getPosition() + offset);

Parameters

offset Offset

See also: setPosition

void sf::Transformable::rotate ( float angle )

Rotate the object.

This function adds to the current rotation of the object, unlike setRotation which overwrites it. Thus, it is equivalent to the following code:

object.setRotation(object.getRotation() + angle);

Parameters

angle Angle of rotation, in degrees

void sf::Transformable::scale	(	float	factorX,
		float	factorY
	)

Scale the object.

This function multiplies the current scale of the object, unlike setScale which overwrites it. Thus, it is equivalent to the following code:

sf::Vector2f scale = object.getScale();

object.setScale(scale.x * factorX, scale.y * factorY);

Parameters

factorX	Horizontal scale factor
factorY	Vertical scale factor

See also: setScale

void sf::Transformable::scale ( const Vector2f & factor )

Scale the object.

This function multiplies the current scale of the object, unlike setScale which overwrites it. Thus, it is equivalent to the following code:

sf::Vector2f scale = object.getScale();

object.setScale(scale.x * factor.x, scale.y * factor.y);

Parameters

factor Scale factors

See also: setScale

void sf::Transformable::setOrigin	(	float	x,
		float	y
	)

set the local origin of the object

The origin of an object defines the center point for all transformations (position, scale, rotation). The coordinates of this point must be relative to the top-left corner of the object, and ignore all transformations (position, scale, rotation). The default origin of a transformable object is (0, 0).

Parameters

x	X coordinate of the new origin
y	Y coordinate of the new origin

See also: getOrigin

void sf::Transformable::setOrigin ( const Vector2f & origin )

set the local origin of the object

Parameters

origin New origin

See also: getOrigin

void sf::Transformable::setPosition	(	float	x,
		float	y
	)

set the position of the object

This function completely overwrites the previous position. See the move function to apply an offset based on the previous position instead. The default position of a transformable object is (0, 0).

Parameters

x	X coordinate of the new position
y	Y coordinate of the new position

See also: move, getPosition

void sf::Transformable::setPosition ( const Vector2f & position )

set the position of the object

This function completely overwrites the previous position. See the move function to apply an offset based on the previous position instead. The default position of a transformable object is (0, 0).

Parameters

position New position

See also: move, getPosition

void sf::Transformable::setRotation ( float angle )

set the orientation of the object

This function completely overwrites the previous rotation. See the rotate function to add an angle based on the previous rotation instead. The default rotation of a transformable object is 0.

Parameters

angle New rotation, in degrees

See also: rotate, getRotation

void sf::Transformable::setScale	(	float	factorX,
		float	factorY
	)

set the scale factors of the object

This function completely overwrites the previous scale. See the scale function to add a factor based on the previous scale instead. The default scale of a transformable object is (1, 1).

Parameters

factorX	New horizontal scale factor
factorY	New vertical scale factor

See also: scale, getScale

void sf::Transformable::setScale ( const Vector2f & factors )

set the scale factors of the object

This function completely overwrites the previous scale. See the scale function to add a factor based on the previous scale instead. The default scale of a transformable object is (1, 1).

Parameters

factors New scale factors

See also: scale, getScale

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

Transformable.hpp

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SFML - Simple and Fast Multimedia Library

SFML

Public Member Functions

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation