Twirling Hats

A certain scene in the Syzygy trailer has made me cringe with dread since I first decided to include it. It’s an understated scene, a quiet moment when Amanda wrote a simple action for Tom that precedes a key line of dialogue. In the novel, he’s listening to a tense conversation between three other characters, and he’s twirling his hat on his finger. I picked up a hat and twirled it myself, and learned that it is, in fact, possible to do this without launching the hat clear across the room. But when I contemplated the physics of the interaction between my finger, hand, and the hat, I knew I was going to have quite a challenge when it came to recreating this effect in iClone.

Sure, I could do a simple keyframe animation, rotating the hat manually at regular intervals on the timeline. But I knew even before I experimented with it that this would render a stiff and artificial result. One thing I’m already struggling with is creating realistic and smooth animation. I certainly don’t want to settle for clunky keyframing if there is an alternative.

Thanks to Reallusion, there is. iClone5 gives us tools to assign real-world physics properties to almost any prop, along with a tremendous amount of control over how we use them. I wish I knew more about the history of real time 3D animation, because I’d like to know just how revolutionary these iClone physics properties really are. At this time, I don’t know of any other commercial machinima application that offers this feature.

All this aside, when I tried to animate the twirling hat, I could not, for the life of me, get the correct physics response from a logical sequence of cause and effect. I won’t bore you with all the details, but the short version is that I finally just engineered the thing in reverse. Instead of making the hat respond to the rotation of the hand, I made the hand follow the rotation of the hat. I did this by animating a cylinder, which is invisible in the rendered scene. I put the cylinder into a constant state of rotation using keyframes, then I used it as the kinematic “engine” that drives the hat. I assigned the hat a dynamic physics state and played with pivot points and axis locks until I got the right effect. Then I attached the hand to the hat, and while I had to get extremely creative with dummy props to prevent the wrist from making unnatural 360 degree rotations, I did manage to come up with a fairly convincing animation. Watch the end result here:

This is the first video clip I’ve released from the Syzygy trailer. And while it’s extremely short, it should give everyone an idea of what to expect from the finished product. I slowed these frames down so you’d have time to see the animation, but the twirl is somewhat faster in the trailer.

I’ve also uploaded some more pictures from the set, including two characters Amanda has never seen. They would be Collin, Finn’s father, and Dr. Malum, the evil scientist:

Then, of course, we have Finn, and another snapshot of Tom. The shirt and suspenders combination you see Tom wearing is the very first mesh I created in 3DS Max and imported into iClone. I’m still amazed by the level of detail, and by the sophisticated bone weights that allow the suspenders to drape so naturally across the front of the shirt. Yay, me! I did a heck of a job with that outfit, even if I do say so myself.


Finn jumping onto the roof with Bea:

And here is Bea on the roof. She’s dressed to match the novel’s description of her as closely as possible. Please notice that her skirt folds and drapes to the ground rather than sticking out around her legs like a bell. This was a very big deal for me, as it was my first experience with “Flowcloth.” “Flowcloth” is a third-party creation offered by a developer called “Apparition” in the Reallusion Marketplace. It’s the first third-party content I’ve had to purchase, and I didn’t  buy it only for Amanda’s trailer. This is something I will be able to customize and use over and over again for any character wearing a dress.

When I made the “Left On Stonehaven” machinima based on Carol Kean’s novel (using Sims 2 as the platform, not iClone) , I had to actually create two separate meshes for the Romany character to wear as she slid down the wall—one that was shaped normally and one that was fitted around her legs once she was sitting. Keep in mind that every mesh is “stiff” without physics properties, and while they move with the bones they’re assigned to, they do not respond to gravity or other “natural” forces. Therefore if I’d left her in the original nightgown mesh, the front of it would have poked up above her knees and obscured her face, like a bell lying on its side.

If you look carefully at these photos, you can see the difference between meshes. Also, I’ve included a still shot of a transition frame when neither mesh worked just right and her legs bled through. With the original mesh, the skirt was equidistant from the front of her knee as well as the back of her knee (although it disappeared into the wall behind her. Oh, well.) In the next picture, you can see that the mesh is not equidistant from the sides of her knees at all. This worked great for the final frames when she was sitting, but see what happens during the transition: there is significant bleedthrough in the thigh area. There was nothing I could do about it. I spent several days on this problem and this was the best result I could get. I finally just had to film it and hope the frames went by so quickly that no one would notice.



Thanks to “Apparition,” this issue doesn’t have to be a problem with iClone5. Interested iClone directors can find the Flowcloth here.

Once again, thank you for reading and following my blog. Stay tuned even after I’ve finished and released the “Syzygy” trailer—for my next project, I’ll have to animate a horse. Hearing about my misadventures with that one might make some first rate entertainment!

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4 responses to “Twirling Hats

  1. Wow, I never knew hat twirling would be so complicated. So, essentially you had the hat twirl his finger, rather than the finger twirl the hat. Clever! 🙂 BTW, he looks so good!

  2. He and Finn both are handsome devils, aren’t they? LOL!

  3. This is fascinating. I followed along in awe. The hat twirl looks so realistic.

  4. dolittlesaymuch

    Francene, I’m so glad you’re enjoying these posts. I realize they don’t appeal to everyone–having a huge audience has never been my goal here. But I think this is a very good way to demystify the process for potential or future clients. Speed is my biggest issue right now, because the learning curve is so steep for me. But I’m definitely getting faster as I go, plus I keep every item I make in my props library, so as time goes by I’ll have to spend less and less time meshing stuff like hats and furniture and useless stuff to hang on the set walls just so they won’t be bare. 🙂

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