The animation "core loop"


Game designers have a concept called a “core loop.” That’s the loop of things that your player will be doing over and over again during gameplay. For instance, the core loop for a shooter might be something like:


Game designers spend a lot of time trying to make the core loop fun, because no matter how many higher-level goals you build onto your game, if your game is a shooter then what you will actually be doing moment-to-moment is shooting stuff, so if that’s not fun you don’t have much of a game.

I think the concept of a core loop is useful for describing a lot of activities, especially artistic ones. The core loop for drawing might look like this:


Just as in game design, there are larger loops around that core loop for higher-level goals--in this case your higher-level goals might be things like composition, character design, and perspective. But you’re going to achieve all of those things by drawing a whole lot of lines through the core loop.

For me, at least, the constant cycling through steps of creation and evaluation is really central to creating anything, certainly for animation. Ideally, the animation core loop would look like this:


But it frequently looks more like this:

If you want to animate really fast, then getting this core loop to be as fast as possible is the number one priority, which means kicking out those extraneous steps as much as possible. You can mitigate the second extraneous step by relying on interpolationless animation, or push it to a different, less creatively important step of the process by using a blocking-plus approach and worrying about interpolation later, but that still leaves the cognitive load of thinking about how the motion must be expressed through the rig. Thinking about this has made me reconceive how I’m building the ephemeral rig system, and potentially I may end up having it work quite differently then it does now.

Right now I can take advantage of the ephemeral nature of the rig to make it reconfigurable. To do that, I’ve made a little in-context menu that lets you switch a control or limb to different preset rig states. You can also manually attach nodes together in any order.

But I’ve come to the conclusion that this is still too much effort. Configuring the rig isn’t as bad as thinking about a conventional rig and all of its interpolation issues, but it’s still adding an additional step to the loop. You want to just go in and make the changes you want, not configure something first.

One thing I’m exploring now is having the interaction work more like manipulators then like configuring a rig. I wouldn’t actually be authoring new manipulators, but rather having different manipulation modes that affect the entire rig at once, so that you can switch back and forth between interaction modes with different modifier keys. To do that, I’m going to have to rebuild the system, because right now switching modes on the entire rig is much slower than it should be.

There are a bunch of reasons for that; relying too much on pyMEL is one of them. But in the process of figuring out how to create a more efficient system, I’ve realized that my attempt to hack the Maya scene graph to do what I want with just a little bit of help from om2 is not going to be the most effective way of achieving this, as I keep running into more and more issues reconciling what I’m doing with the rest of Maya’s stuff--managing undo, for instance, is becoming a real mess. In other words, I need to stop thinking like a stereotypical “TD,” hacking together a system out of whatever pieces are already lying around in Maya, and think like a developer, willing to implement my own rigging behavior purely through code that will only pass information back to Maya in specific places. My initial tests of this idea suggest that it will actually be much simpler than the rather baroque system I ended up building around the last iteration of the ephemeral rig concept, and I’ll be documenting my experiments in future posts.

I’m also investigating the exoSwitch constraint, recently released by Tim Naylor and Andrea Maiolo. The exoSwitch constraint is a bi-directional constraint, allowing you to manipulate either side of the constraint connection, which, for one thing, would let you get some basic ephemeral-like behavior without having to build a whole system like I am. While I don’t know how it works under the hood, I’m guessing that it’s passing information behind Maya’s back in a way not dissimilar to the ephemeral rig concept, because that’s really the only way I can imagine getting this behavior working in Maya.

One really nice feature it has is the ability to automatically change the driver of a constraint system based on which control is selected.

Whether or not I end up replacing aspects of the ephemeral rig system with the exoSwitch constraint, making rig behavior dependent on context like what control is selected is a really good idea that I want to use to remove even more extraneous thought from that loop. I’ll post more about it once I have a chance to test it out more.