This post is less of a tutorial, and more of a shout-out to an incredible piece of software that I have relied upon many times over the years. The following animation is something I created without the use of keyframes. Not a single keyframe was needed to create this piece. Seriously.
Newton 2 is a physics engine developed specifically for After Effects. Not only is it incredibly powerful, it's also very easy to use. Each shape layer loaded in to Newton 2 is given a long list of attributes for you to manipulate to your hearts content, making it very quick to replicate the properties of any material you can think of. Not only that, your shapes can be connected via several types of joints, supported by springs, or even powered by motors. The limit is literally your own imagination.
The 'Collision' project was a way for me to push what Newton is capable of, as the prospect of being able to create a full short animation without actually animating anything was just too tempting. But this is an extreme example of what you might use Newton 2 for.
I rely on Newton 2 frequently for my projects, but tend to use it very sparingly, mainly for small moments of complicated animation that would normally be too difficult to figure out, or just take far too long to animate in a realistic way. One of my favourite examples of this is in a short looping animation I created called 'Ritual' (below). All the bones in this project were animated using Newton 2. The skeleton was given joints that connected all the parts together, just as they would be in the real-world. The spine that swings from the characters skull-helmet is driven by the animation of the head using Newton 2. Once it was all set up, all I had to do was press GO, and I had a beautifully realistic (if slightly macabre) swinging spine.
You can try or purchase Newton 2 from Motion Boutique, where you'll also find loads of helpful tutorials to get you started with the plugin. Once you get to grips, you'll want to find a use for Newton 2 in all of your future projects!