flash.geom.PerspectiveProjection - Adobe® Flex® 4 Language Reference (Flex 4)

Package	flash.geom
Class	public class PerspectiveProjection
Inheritance	PerspectiveProjection Object

Language Version:

ActionScript 3.0

Runtime Versions:

Flash Player 10, AIR 1.5

The PerspectiveProjection class provides an easy way to assign or modify the perspective transformations of a display object and all of its children. For more complex or custom perspective transformations, use the Matrix3D class. While the PerspectiveProjection class provides basic three-dimensional presentation properties, the Matrix3D class provides more detailed control over the three-dimensional presentation of display objects.

Projection is a way of representing a three-dimensional object in a two-dimensional space, like a cube projected onto a computer screen. Perspective projection uses a viewing frustum (a rectangular pyramid) to model and project a three-dimensional world and its objects on the screen. The viewing frustum becomes increasingly wider as it moves further from the origin of the viewpoint. The origin of the viewpoint could be a camera or the eyes of an observer facing the screen. The projected perspective produces the illusion of three dimensions with depth and distance, where the objects closer to the screen appear larger than the objects farther from the screen.

Frustum viewing area

A default PerspectiveProjection object is a framework defined for perspective transformation of the root object, based on the field of view and aspect ratio (dimensions) of the stage. The projection center, the vanishing point, is set to the center of the stage, which means the three-dimensional display objects disappear toward the center of the stage as they move back in the z axis. The default viewpoint is at point (0,0) looking down the positive z axis. The y-axis points down toward the bottom of the screen. You can gain access to the root display object's perspective projection settings and change the field of view and projection center properties of the perspectiveProjection property through the root object's DisplayObject.transform property.

You can also set a different perspective projection setting for a display object through the parent's perspective projection. First, create a PerspectiveProjection object and set its fieldOfView and projectionCenter properties. Next, assign the PerspectiveProjection object to the parent display object using the DisplayObject.transform property. The specified projection matrix and transformation will then apply to all the display object's three-dimensional children.

Public Properties

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	Property		Defined By
		constructor : Object A reference to the class object or constructor function for a given object instance.	Object
		fieldOfView : Number Specifies an angle, as a degree between 0 and 180, for the field of view in three dimensions.	PerspectiveProjection
		focalLength : Number The distance between the eye or the viewpoint's origin (0,0,0) and the display object located in the z axis.	PerspectiveProjection
		projectionCenter : Point A two-dimensional point representing the center of the projection, the vanishing point for the display object.	PerspectiveProjection
		prototype : Object [static] A reference to the prototype object of a class or function object.	Object

Public Methods

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	Method		Defined By
		PerspectiveProjection() Creates an instance of a PerspectiveProjection object.	PerspectiveProjection
		hasOwnProperty(name:String):Boolean Indicates whether an object has a specified property defined.	Object
		isPrototypeOf(theClass:Object):Boolean Indicates whether an instance of the Object class is in the prototype chain of the object specified as the parameter.	Object
		propertyIsEnumerable(name:String):Boolean Indicates whether the specified property exists and is enumerable.	Object
		setPropertyIsEnumerable(name:String, isEnum:Boolean = true):void Sets the availability of a dynamic property for loop operations.	Object
		toLocaleString():String Returns the string representation of this object, formatted according to locale-specific conventions.	Object
		toMatrix3D():Matrix3D Returns the underlying Matrix3D object of the display object.	PerspectiveProjection
		toString():String Returns the string representation of the specified object.	Object
		valueOf():Object Returns the primitive value of the specified object.	Object

Property Detail

fieldOfView

property

fieldOfView:Number

Language Version:

ActionScript 3.0

Runtime Versions:

Flash Player 10, AIR 1.5

Specifies an angle, as a degree between 0 and 180, for the field of view in three dimensions. This value determines how strong the perspective transformation and distortion apply to a three-dimensional display object with a non-zero z-coordinate.

A degree close to 0 means that the screen's two-dimensional x- and y-coordinates are roughly the same as the three-dimensional x-, y-, and z-coordinates with little or no distortion. In other words, for a small angle, a display object moving down the z axis appears to stay near the same size and moves little.

A value close to 180 degrees results in a fisheye lens effect: positions with a z value smaller than 0 are magnified, while positions with a z value larger than 0 are minimized. With a large angle, a display object moving down the z axis appears to change size quickly and moves a great distance. If the field of view is set to 0 or 180, nothing is seen on the screen.

Implementation
public function get fieldOfView():Number
public function set fieldOfView(value:Number):void

focalLength

property

focalLength:Number

Language Version:

ActionScript 3.0

Runtime Versions:

Flash Player 10, AIR 1.5

The distance between the eye or the viewpoint's origin (0,0,0) and the display object located in the z axis. During the perspective transformation, the focalLength is calculated dynamically using the angle of the field of view and the stage's aspect ratio (stage width divided by stage height).

Implementation
public function get focalLength():Number
public function set focalLength(value:Number):void

projectionCenter

property

projectionCenter:Point

Language Version:

ActionScript 3.0

Runtime Versions:

Flash Player 10, AIR 1.5

A two-dimensional point representing the center of the projection, the vanishing point for the display object.

The projectionCenter property is an offset to the default registration point that is the upper left of the stage, point (0,0). The default projection transformation center is in the middle of the stage, which means the three-dimensional display objects disappear toward the center of the stage as they move backwards in the z axis.

Implementation
public function get projectionCenter():Point
public function set projectionCenter(value:Point):void

Constructor Detail

PerspectiveProjection

()

Constructor

public function PerspectiveProjection()

Language Version:

ActionScript 3.0

Runtime Versions:

Flash Player 10, AIR 1.5

Creates an instance of a PerspectiveProjection object.

Method Detail

toMatrix3D

()

method

public function toMatrix3D():Matrix3D

Language Version:

ActionScript 3.0

Runtime Versions:

Flash Player 10, AIR 1.5

Returns the underlying Matrix3D object of the display object.

A display object, like the root object, can have a PerspectiveProjection object without needing a Matrix3D property defined for its transformations. In fact, use either a PerspectiveProjection or a Matrix3D object to specify the perspective transformation. If when using the PerspectiveProjection object, a Matrix3D object was needed, the toMatrix3D() method can retrieve the underlying Matrix3D object of the display object. For example, the toMatrix3D() method can be used with the Utils3D.projectVectors() method.

Returns

Matrix3D — The underlying Matrix3D object.