Things to consider when defining default animation timings and easings for user interfaces

I meant to rewrite this nicely a long time ago, never got down to re-writing it. And yet... it seems like it could help people. So here's the original braindump version.

Default timing for animations == 200ms. Default easing == Ease In-Out

This is the simplest way to achieve what we want, in terms of animation.

What we are doing here can be considered "semantic" animation, as it is the animations that "explain" to the user why and how the map is being displayed to them. The equivalent is a book opening, or a page turning.

If possible, make the timings and the animation types customisable, with defaults.

Why 200ms?
Because when it comes to things we interact with mostly visually, 200ms is the amount of time it takes the human brain to register that something has come into view, or changed. At 200ms, UI animation feels almost instant.

Now, we could get pickier, and make it 300-400ms for XS, SM, and 200ms for MD, L, XL, because the distance travelled by the animated objects also influences how fast they feel. However, this lies in the realm of "fancy extras". They are nice, but if we start doing that, then to be consistent, we need to do it EVERYWHERE.

So 200ms. ;) For everything.

Please note that this is a visual thing. If you are writing with a stylus, and the lag is 200ms (or you're gaming! ;) ) 200ms, is way way way too slow. When writing with a digital stylus, or drawing with a mouse, the latency has to be as close to 0 as possible. Even 100ms feels laggy when you draw with a stylus or a mouse.

Why Ease In-Out?
Easing makes animations look more natural, by visually mimicking the laws of physics.

We're using Ease In-Out as the default, as it mimics physics, AND is less confusing for most people who aren't professional animators.

But whyyyyy! ;) Ok here's why...

If we wanted to be picky, when something animates INTO view, we should use Ease-Out. Ease-Out is when something moves fast at first, and then slows down. This mimics physics in the real world, where stuff loses momentum as it moves, due to friction. So it starts fast (because as it's animating into our view, it's already moving), and as it runs out of energy, it slows down.

Likewise, when something animates OUT OF view, we should use Ease-In. Ease-In is when something moves slowly at first, and then speeds up. Again, this mimics physics in the real world, where it takes time for stuff to build up momentum, and then it goes faster as it collects enough energy to overcome friction. So it starts slow (because it's charging up, while still being in our view), and then the animation speeds up as the item leaves our view.

^And yes, for stuff that comes INTO view, it's better to use Ease-OUT, for stuff that LEAVES our view, it's better to use Ease-IN. Yes. It's horribly confusing.

Ease In-Out to the rescue! ;) Our :X compromised best of both worlds. It's not really... but it's the least confusing to remember.

Ease In-Out is when something moves quickly at first, slows down... then speeds back up. In UI terms, this is a nice compromise if we don't wanna be fancy, because as humans, we're lazy about how we perceive things.

When we use Ease In-Out for something that animates INTO view, the human-goldfish mind has most likely already stopped paying attention before the last "fast" in the fast-slow-fast sequence. So to the human-goldfish, most of the time it'll look like an Ease-Out.

When we use Ease-In-Out for something that animates OUT of view, the human-goldfish mind (you see where this is going) takes a while to notice what's going on. ;) So it likely doesn't notice the first "fast" in the fast-slow-fast sequence.

Some samples, using 200ms and (naughty naughty, ALL ease-in).
Each click as shown is triggering a new 200ms animation to the next keyframe.