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Rigging and animating for the apocalypse
by Sterling Reames on 02/03/14 11:28:00 am   Featured Blogs

The following blog post, unless otherwise noted, was written by a member of Gamasutra’s community.
The thoughts and opinions expressed are those of the writer and not Gamasutra or its parent company.

 

This is a re-blog of my original post at Proletariat.com. Please feel free to click the image above or download World Zombination character rig here! Let me know in the comments if you have any questions, thanks!

One of our design goals for World Zombination is to have lots of unique characters. Larger studios solve this problem by hiring a technical artist with years of scripting experience to create auto-rigging solutions, or by using brute force and throwing many artists at the work. Despite neither of these options being available, we’ve built an animation pipeline that minimizes the time spent rigging 3D characters, shares a single character rig across a number of uniquely proportioned characters, and shares animations across those characters.

 image

I don’t have much scripting experience with Autodesk Maya, so I decided to find a way to setup visual controls for repositioning bones using Maya’s built-in tools. This retargeting  would have to automatically reposition IK handles and all animation controls, without having to tear down and setup the connections again. Much easier said than done.

image

After some experimentation, I came to an overall setup like the diagram above. Translating the retarget controls drives the animation controls, which in turn drive bone movement. No matter how the animation controls are repositioned, the bones always follow. A small caveat with this setup is that we aren’t able to use Maya’s point constraints on any animation controls; we’re limited to direct connections using math nodes. Luckily, our setup is simple enough to work with this restriction.

FK/IK repositioning was something I struggled to build, as the IK solver tends to rotate bones when repositioning the retarget controls. To work around this, I connected the translate attributes of the end joints (wrist and ankles) to the effector of each IK handle. The effector determines the start point of the IK solver. So, if the bone and effector move at the same time, the solver behaves as though the bone hasn’t moved at all, thus eliminating unwanted bone rotation.

image

All of our characters share a single rig, which means they can also share animations! Since the retarget controls operate separately from animation controls, the animation curves remain untouched when switching between characters. We still create unique animations for each character, but it’s great to be able to quickly create assets for programmers to work with. Really, this feature is the result of a happy accident, but I didn’t mind taking all the credit (haha).

image

The character rig took quite a bit of time to create, most of which was spent experimenting, but this up front work has already saved us months of work hours. The extensibility of this retarget rig far exceeded my expectations, especially given my lack of experience with complex rigging setups. The retargeting allows for all the animation controls I want, IK/FK switching, non-uniform scaling (squash and stretch), and animation sharing across any number of characters.

If you’re already familiar with Maya, check out the World Zombination character rig by downloading it, as is, here. Let me know what you think and/or if you have any questions at sterling@proletariat.com. There are seven characters included with the animation rig and instructions to add your own bipedal characters. Enjoy!

-Sterling Reames
Sr. Animator - Proletariat Inc.


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Comments


Andy Cahalan
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Wow. That's a hell of a random act of kindness, Mr. Reames.

Sterling Reames
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Thanks Andy! As a smaller studio, it's easy to get lost in the sea of games out there; so we're pulling out all the stops this time around. We decided as a team that this would be a great opportunity to give back, but also get our game out there too. Perhaps when fortunes change we'll think differently, but for now, getting our name out there is an invaluable asset to our success.

Justin Rojas
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As a new small Indie developer I am limited on the number of artists that I have to work with and this just might make a huge difference for us to be able to get some of our stuff out there as well. I really appreciate you giving back like this and I hope that I will be able to do the same one day. Thanks

Sterling Reames
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No problem Justin. Glad we could help! While I do have instructions with the rig, adding your own characters will take a bit of Maya knowledge. We didn't intend to release this to the public originally, so it's not 100% user friendly, but certainly better than starting from scratch.

TC Weidner
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Very nice.

Dan Jones
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Wow! To echo what has already been said, this is very cool of you.

I'm looking forward to tinkering with it as soon as I get a chance. Also, I'm really digging the character style for World Zombination and I'll definitely keep it on my radar.

Thanks!

Ryan Christensen
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Awesome stuff, a bit like mecanim in unity. The art and assets are very cool as well, will definitely check the game out this year. Love the entire art direction from character to the site (http://worldzombination.com/) to the brand and naming. Seems the character designs are so well done they would meet the 'identifiable character by shadow/silhouette' art direction from TF2. Definitely on the right track with the art and smart solutions like this.

Sterling Reames
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Thanks Ryan! It's funny you mention Unity, because we originally built the rig to work with mecanim, but after many failed attempts of getting non-uniform bone scaling to work we ended up with a pre-rendered approach.

Our art director, Damon Iannuzzelli, deserves most of the props on the whole character and branding look. To be compared to Valve is definitely a compliment! :)

James Yee
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Bravo! Thanks!

I wonder if something similar can be done in Blender and other systems?

Justin Rojas
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I have played around with it just to see what it can do, but I will be talking to my artist to see if it will help him out for our next project. I can't wait for us to be able to really dive into it and see what we can do with it. Thanks again


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