Squash

Automatic squash/stretch animated subclasses of UIView and CALayer.

SMSquashView and its backing class, SMSquashLayer, squash and stretch themselves automatically in response to motion. They will distort themselves longer in the direction of motion, and shorter in the perpendicular directions. The distortion is proportional to the velocity the object, and scaled such that the volume remains constant. In short: it does exactly what you’d want it to do, with no configuration required.

How It Works

The math is pretty simple, if you like transformation matrices. Every time the layer’s position changes, we note the time and position delta from last time. Using that information we can calculate the velocity for the current frame of animation. We align a transformation matrix to the direction of travel using the same idea as gluLookAt, then scale according to the magnitude of the velocity.

How to Use It

Seriously, just drop it in. It supports all the customization you could want:

squashFactor represents the speed above which an object must move to be distorted
maxStretch puts a ceiling on the amount of stretching an object can do
minSquash puts a floor on it
smoothMotion will run a moving average filter to smooth out motion jaggies

…but these are all set to very reasonable values. You may not need to change them.

What's It Look Like

More Info

The original blog post for this project can be found here.

LICENSE

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.