PhysicsPropsPlugin

Sometimes it's useful to tween a value at a particular velocity and/or acceleration without a specific end value in mind. PhysicsPropsPlugin allows you to tween any numeric property of any object based on these concepts. Keep in mind that any easing equation you define for your tween will be completely ignored for these properties. Instead, the physics parameters will determine the movement/easing.

These parameters, by the way, are not intended to be dynamically updateable, but one unique convenience is that everything is reverseable. So if you create several physics-based tweens, for example, and throw them into a timeline, you could simply call reverse() on the timeline to watch the objects retrace their steps right back to the beginning. Here are the parameters you can define (note that friction and acceleration are both completely optional):

• velocity : Number - The initial velocity of the object measured in units per second (or for tweens where useFrames is true, it would be measured per frame). (Default: 0)
• acceleration : Number - The amount of acceleration applied to the object, measured in units per second (or for tweens where useFrames is true, it would be measured per frame). (Default: 0)
• 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 it 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, starting at a very low value like 0.02. Also note that friction requires more processing than physics tweens without any friction. (Default: 0)

gsap.to(elem, {
  duration: 2,
  physicsProps: {
     x: {velocity: 100, acceleration: 200},
     y: {velocity: -200, friction: 0.1}
   }
});

Demos

• PhysicsProps Demos

To learn how to include the PhysicsPropsPlugin into your project, see the GSAP install docs.