Provides simple physics functionality for tweening a DisplayObject's x and y coordinates based on a
combination of velocity, angle, gravity, acceleration, accelerationAngle, and/or friction. It is not intended
to replace a full-blown physics engine and does not offer collision detection, but serves
as a way to easily create interesting physics-based effects with the GreenSock tweening platform. Parameters
are not intended to be dynamically updateable, but one unique convenience is that everything is reverseable.
So if you spawn a bunch of particle tweens, for example, and throw them into a TimelineLite, you could
simply call reverse() on the timeline to watch the particles retrace their steps right back to the beginning.
Keep in mind that any easing equation you define for your tween will be completely ignored for these properties.
- velocity : Number - the initial velocity of the object measured in pixels per time
unit (usually seconds, but for tweens where useFrames is true, it would
be measured in frames). The default is zero.
- angle : Number - the initial angle (in degrees) at which the object is traveling. Only
pertinent when a velocity is defined. For example, if the object should
start out traveling at -60 degrees (towards the upper right), the angle
would be -60. The default is zero.
- gravity : Number - the amount of downwards acceleration applied to the object, measured
in pixels per time unit (usually seconds, but for tweens where useFrames
is true, it would be measured in frames). You can either use
gravity
or acceleration, not both because gravity is the same thing
as acceleration applied at an accelerationAngle of 90. Think of gravity
as a convenience property that automatically sets the accelerationAngle
for you.
- acceleration : Number - the amount of acceleration applied to the object, measured
in pixels per time unit (usually seconds, but for tweens where useFrames
is true, it would be measured in frames). To apply the acceleration in a specific
direction that is different than the
angle, use the accelerationAngle
property. You can either use gravity
or acceleration, not both because gravity is the same thing
as acceleration applied at an accelerationAngle of 90.
- accelerationAngle : Number - the angle at which acceleration is applied (if any), measured in degrees.
So if, for example, you want the object to accelerate towards the left side of the
screen, you'd use an
accelerationAngle of 180. If you define a
gravity value, it will automatically set the accelerationAngle
to 90 (downwards).
- friction : Number - a value between 0 and 1 where 0 is no friction, 0.08 is a small amount of
friction, and 1 will completely prevent any movement. This is not meant to be precise or
scientific in any way, but rather serves as an easy way to apply a friction-like
physics effect to your tween. Generally it is best to experiment with this number a bit.
Also note that friction requires more processing than physics tweens without any friction.
USAGE:
import com.greensock.TweenLite;
import com.greensock.plugins.TweenPlugin;
import com.greensock.plugins.Physics2DPlugin;
TweenPlugin.activate([Physics2DPlugin]); //activation is permanent in the SWF, so this line only needs to be run once.
TweenLite.to(mc, 2, {physics2D:{velocity:300, angle:-60, gravity:400}});
//--OR--
TweenLite.to(mc, 2, {physics2D:{velocity:300, angle:-60, friction:0.1}});
//--OR--
TweenLite.to(mc, 2, {physics2D:{velocity:300, angle:-60, acceleration:50, accelerationAngle:180}});
Physics2DPlugin is a Club GreenSock membership benefit. You must have a valid membership to use this class
without violating the terms of use. Visit http://blog.greensock.com/club/ to sign up or get more details.
Copyright 2009, 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 function Physics2DPlugin()
TweenPlugin
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