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Class CirclePath2D

Package | com.greensock.motionPaths
Class | public class CirclePath2D
Inheritance | CirclePath2D MotionPath flash.display.Shape

A CirclePath2D defines a circular path on which a PathFollower can be placed, making it simple to tween objects along a circle or oval (make an oval by altering the width/height/scaleX/scaleY properties). A PathFollower's position along the path is described using its `progress` property, a value between 0 and 1 where 0 is at the beginning of the path, 0.5 is in the middle, and 1 is at the very end of the path. So to tween a PathFollower along the path, you can simply tween its `progress` property. To tween ALL of the followers on the path at once, you can tween the CirclePath2D's `progress` property. PathFollowers automatically wrap so that if the `progress` value exceeds 1 or drops below 0, it shows up on the other end of the path.
Since CirclePath2D extends the Shape class, you can add an instance to the display list to see a line representation of the path drawn which can be helpful especially during the production phase. Use `lineStyle()` to adjust the color, thickness, and other attributes of the line that is drawn (or set the CirclePath2D's `visible` property to false or don't add it to the display list if you don't want to see the line at all). You can also adjust all of its properties like `radius, scaleX, scaleY, rotation, width, height, x,` and `y`. That means you can tween those values as well to achieve very dynamic, complex effects with ease.

Example
Example AS3 code:

    import com.greensock.*;
    import com.greensock.plugins.*;
    import com.greensock.motionPaths.*;
    TweenPlugin.activate([CirclePath2DPlugin]); //only needed once in your swf, and only if you plan to use the CirclePath2D tweening feature for convenience

    //create a circle motion path at coordinates x:150, y:150 with a radius of 100
    var circle:CirclePath2D = new CirclePath2D(150, 150, 100);

    //tween mc along the path from the bottom (90 degrees) to 315 degrees in the counter-clockwise direction and make an extra revolution
    TweenLite.to(mc, 3, {circlePath2D:{path:circle, startAngle:90, endAngle:315, direction:Direction.COUNTER_CLOCKWISE, extraRevolutions:1}});

    //tween the circle's rotation, scaleX, scaleY, x, and y properties:
    TweenLite.to(circle, 3, {rotation:180, scaleX:0.5, scaleY:2, x:250, y:200});

    //show the path visually by adding it to the display list (optional)
    this.addChild(circle);

    //--- Instead of using the plugin, you could manually manage followers and tween their "progress" property...

    //make the MovieClip "mc2" follow the circle and start at a position of 90 degrees (this returns a PathFollower instance)
    var follower:PathFollower = circle.addFollower(mc2, circle.angleToProgress(90));

    //tween the follower clockwise along the path to 315 degrees
    TweenLite.to(follower, 2, {progress:circle.followerTween(follower, 315, Direction.CLOCKWISE)});

    //tween the follower counter-clockwise to 200 degrees and add an extra revolution
    TweenLite.to(follower, 2, {progress:circle.followerTween(follower, 200, Direction.COUNTER_CLOCKWISE, 1)});

NOTES

- All followers's positions are automatically updated when you alter the MotionPath that they're following.
- To tween all followers along the path at once, simply tween the MotionPath's `progress` property which will provide better performance than tweening each follower independently.

Copyright 2011, GreenSock. All rights reserved. This work is subject to the terms in http://www.greensock.com/terms_of_use.html or for corporate Club GreenSock members, the software agreement that was issued with the corporate membership.

Public Properties
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| Property | Defined by
--- | --- | ---
|  | followers : Array Returns an array of all PathFollower instances associated with this path | MotionPath
|  | height : Number | MotionPath
|  | progress : Number A value between 0 and 1 that can be used to move all followers along the path. | MotionPath
|  | radius : Number radius of the circle (does not factor in any transformations like scaleX/scaleY) | CirclePath2D
|  | rawProgress : Number Identical to `progress` except that the value is not re-interpolated between 0 and 1. | MotionPath
|  | rotation : Number | MotionPath
|  | scaleX : Number | MotionPath
|  | scaleY : Number | MotionPath
|  | targets : Array Returns an array of all target instances associated with the PathFollowers of this path | MotionPath
|  | visible : Boolean | MotionPath
|  | width : Number | MotionPath
|  | x : Number | MotionPath
|  | y : Number | MotionPath

Public Methods
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| Method | Defined by
--- | --- | ---
|  | CirclePath2D(x:Number, y:Number, radius:Number) Constructor | CirclePath2D
|  | addFollower(target:*, progress:Number = 0, autoRotate:Boolean = false, rotationOffset:Number = 0):PathFollower Adds a follower to the path, optionally setting it to a particular progress position. | MotionPath
|  | anglesToProgressChange(startAngle:Number, endAngle:Number, direction:String = "clockwise", extraRevolutions:uint = 0, useRadians:Boolean = false):Number Returns the amount of `progress` change between two angles on the CirclePath2D, allowing special parameters like direction and extraRevolutions. | CirclePath2D
|  | angleToProgress(angle:Number, useRadians:Boolean = false):Number Translates an angle (in degrees or radians) to the associated progress value on the CirclePath2D. | CirclePath2D
|  | distribute(targets:Array = null, min:Number = 0, max:Number = 1, autoRotate:Boolean = false, rotationOffset:Number = 0):void Distributes objects evenly along the MotionPath. | MotionPath
|  | followerTween(follower:*, endAngle:Number, direction:String = "clockwise", extraRevolutions:uint = 0, useRadians:Boolean = false):String Simplifies tweening by determining a relative change in the progress value of a follower based on the endAngle, direction, and extraRevolutions that you define. | CirclePath2D
|  | getFollower(target:Object):PathFollower Returns the PathFollower instance associated with a particular target or null if none exists. | MotionPath
|  | lineStyle(thickness:Number = 1, color:uint = 0x666666, alpha:Number = 1, pixelHinting:Boolean = false, scaleMode:String = "none", caps:String = null, joints:String = null, miterLimit:Number = 3, skipRedraw:Boolean = false):void Sets the line style for the path which you will only see if you add the path to the display list with something like addChild() and make sure the visible property is true. | MotionPath
|  | progressToAngle(progress:Number, useRadians:Boolean = false):Number Translates a progress value (typically between 0 and 1 where 0 is the beginning of the path, 0.5 is in the middle, and 1 is at the end) to the associated angle on the CirclePath2D. | CirclePath2D
|  | removeAllFollowers():void Removes all followers. | MotionPath
|  | removeFollower(target:*):void Removes the target as a follower. | MotionPath
|  | renderObjectAt(target:Object, progress:Number, autoRotate:Boolean = false, rotationOffset:Number = 0):void Positions any object with x and y properties on the path at a specific progress position. | CirclePath2D
|  | update(event:Event = null):void Forces the MotionPath to re-render itself and all of its followers. | CirclePath2D

Property detail

radius | property

`radius:Number` [read-write]

radius of the circle (does not factor in any transformations like scaleX/scaleY)

Implementation
`public function get radius():Number`
`public function set radius(value:Number):void`
Constructor detail

CirclePath2D | () | constructor

`public function CirclePath2D(x:Number, y:Number, radius:Number)`

Constructor

Parameters

| `x:Number` — The x coordinate of the origin (center) of the circle
| `y:Number` — The y coordinate of the origin (center) of the circle
| `radius:Number` — The radius of the circle

Method detail

anglesToProgressChange | () | method

`public function anglesToProgressChange(startAngle:Number, endAngle:Number, direction:String = "clockwise", extraRevolutions:uint = 0, useRadians:Boolean = false):Number`

Returns the amount of `progress` change between two angles on the CirclePath2D, allowing special parameters like direction and extraRevolutions.

Parameters

| `startAngle:Number` — The starting angle
| `endAngle:Number` — The ending angle
| `direction:String` (default = "`clockwise`")`` — The direction in which to travel - options are `Direction.CLOCKWISE` ("clockwise"), `Direction.COUNTER_CLOCKWISE` ("counterClockwise"), or `Direction.SHORTEST` ("shortest").
| `extraRevolutions:uint` (default = `0`)`` — If instead of going directly to the endAngle, you want the target to travel one or more extra revolutions around the path before going to the endAngle, define that number of revolutions here.
| `useRadians:Boolean` (default = `false`)`` — If you prefer to define the angle in radians instead of degrees, set this to true (it is false by default)

Returns

| `Number` — A Number representing the amount of change in the `progress` value.

angleToProgress | () | method |

`public function angleToProgress(angle:Number, useRadians:Boolean = false):Number`

Translates an angle (in degrees or radians) to the associated progress value on the CirclePath2D. For example, to position `mc` on the CirclePath2D at 90 degrees (bottom), you'd do:
`var follower:PathFollower = myCircle.addFollower(mc, myCircle.angleToProgress(90));
`

Parameters

| `angle:Number` — The angle whose progress value you want to determine
| `useRadians:Boolean` (default = `false`)`` — If you prefer to define the angle in radians instead of degrees, set this to true (it is false by default)

Returns

| `Number` — The progress value associated with the angle

followerTween | () | method |

`public function followerTween(follower:*, endAngle:Number, direction:String = "clockwise", extraRevolutions:uint = 0, useRadians:Boolean = false):String`

Simplifies tweening by determining a relative change in the progress value of a follower based on the endAngle, direction, and extraRevolutions that you define. For example, to tween `myFollower` from wherever it is currently to the position at 315 degrees, moving in the COUNTER_CLOCKWISE direction and going 2 extra revolutions, you could do:
`TweenLite.to(myFollower, 2, {progress:myCircle.followerTween(myFollower, 315, Direction.COUNTER_CLOCKWISE, 2)});`

Parameters

| `follower:*` — The PathFollower (or its associated target) that will be tweened (determines the start angle)
| `endAngle:Number` — The destination (end) angle
| `direction:String` (default = "`clockwise`")`` — The direction in which to travel - options are `Direction.CLOCKWISE` ("clockwise"), `Direction.COUNTER_CLOCKWISE` ("counterClockwise"), or `Direction.SHORTEST` ("shortest").
| `extraRevolutions:uint` (default = `0`)`` — If instead of going directly to the endAngle, you want the target to travel one or more extra revolutions around the path before going to the endAngle, define that number of revolutions here.
| `useRadians:Boolean` (default = `false`)`` — If you prefer to define the angle in radians instead of degrees, set this to true (it is false by default)

Returns

| `String` — A String representing the amount of change in the `progress` value (feel free to cast it as a Number if you want, but it returns a String because TweenLite/Max/Nano recognize Strings as relative values.

progressToAngle | () | method |

`public function progressToAngle(progress:Number, useRadians:Boolean = false):Number`

Translates a progress value (typically between 0 and 1 where 0 is the beginning of the path, 0.5 is in the middle, and 1 is at the end) to the associated angle on the CirclePath2D. For example, to find out what angle a particular PathFollower is at, you'd do:
`var angle:Number = myCircle.progressToAngle(myFollower.progress, false);
`

Parameters

| `progress:Number` — The progress value to translate into an angle
| `useRadians:Boolean` (default = `false`)`` — If you prefer that the angle be described in radians instead of degrees, set this to true (it is false by default)

Returns

| `Number` — The angle (in degrees or radians depending on the useRadians value) associated with the progress value.

renderObjectAt | () | method |

`public override function renderObjectAt(target:Object, progress:Number, autoRotate:Boolean = false, rotationOffset:Number = 0):void`

Positions any object with x and y properties on the path at a specific progress position. For example, to position `mc` in the middle of the path, you would do:
`myPath.renderObjectAt(mc, 0.5);`
Some paths have methods to translate other meaningful information into a progress value, like for a `CirclePath2D` you can get the progress associated with the 90-degree position with the `angleToPosition()` method like this:
`myCircle.renderObjectAt(mc, myCircle.angleToProgress(90));`

Parameters

| `target:Object` — The target object to position
| `progress:Number` — The progress value (typically between 0 and 1 where 0 is the beginning of the path, 0.5 is in the middle, and 1 is at the end)
| `autoRotate:Boolean` (default = `false`)`` — When `autoRotate` is `true`, the target will automatically be rotated so that it is oriented to the angle of the path. To offset this value (like to always add 90 degrees for example), use the `rotationOffset` property.
| `rotationOffset:Number` (default = `0`)`` — When `autoRotate` is `true`, this value will always be added to the resulting `rotation` of the target.

update | () | method |

`public override function update(event:Event = null):void`

Forces the MotionPath to re-render itself and all of its followers.

Parameters

| `event:Event` (default = `null`)`` — An optional Event that is accepted just to make it easier for use as an event handler (to have it update automatically on every frame, for example, you could add an ENTER_FRAME listener and point it to this method).