Real-time Motion Retargeting to Highly Varied User-Created Morphologies

Chris Hecker   Bernd Raabe   Ryan W. Enslow
John DeWeese   Jordan Maynard   Kees van Prooijen

SIGGRAPH 2008 Technical Paper

Abstract

Character animation in video games—whether manually key-framed or motion captured—has traditionally relied on codifying skeletons early in a game's development, and creating animations rigidly tied to these fixed skeleton morphologies. This paper introduces a novel system for animating characters whose morphologies are unknown at the time the animation is created. Our authoring tool allows animators to describe motion using familiar posing and key-framing methods. The system records the data in a morphology-independent form, preserving both the animation's structural relationships and its stylistic information. At runtime, the generalized data are applied to specific characters to yield pose goals that are supplied to a robust and efficient inverse kinematics solver. This system allows us to animate characters with highly varying skeleton morphologies that did not exist when the animation was authored, and, indeed, may be radically different than anything the original animator envisioned.

Materials

This is the final submitted draft of our paper on the Spore procedural animation system. It's a pretty long paper, barely squeezing into 11 pages, and it still leaves out tons of details, but hopefully it gives a reasonable overview of both the authoring system, using our custom OpenGL animation tool Spasm, and runtime playback system. If you have questions about something in the paper, just email and ask, and I'll update the FAQ section below.

• The paper (PDF, 3.8MB). Most of the embedded images in this PDF are at full resolution, so you can zoom way in to see details that are hard to see at print resolution. Yay, computers!

• The BibTeX entry. This is currently incomplete since the proceedings have not been published yet, but I will update it when I get the ISBN, DOI, and page numbers. I wish more authors would put pre-made BibTeX entries up next to their papers, it is quite handy when you're trying to cite related work! And, it is inexcusable when one of these lame paywall protected journal sites doesn't at least have a free BibTeX entry on the teaser page.

@inproceedings{sporeanim,
 author = {Chris Hecker and Bernd Raabe and Ryan W. Enslow and 
           John DeWeese and Jordan Maynard and Kees van Prooijen},
 title = {Real-time Motion Retargeting to Highly Varied User-Created Morphologies},
 booktitle = {Proceedings of ACM SIGGRAPH '08},
 note={\url{http://chrishecker.com/Real-time_Motion_Retargeting_to_Highly_Varied_User-Created_Morphologies}},
 year = {2008} }

• The videos. Here are the videos from the paper submission. They're quite rough...we were close to the submission deadline so I just turned on FRAPS and winged it. It shows! There are two videos, both available in Xvid avi and QuickTime mp4. The mp4 is higher quality in each case:
  • The first video shows generalization and specialization across a bunch of creatures and different animations. mp4 (27mb) or avi (26mb)
  • The second video shows the jiggles secondary system and the gait system. mp4 (29mb) or avi (27mb)

• My related 2007 Game Developers Conference lecture on the same topic, How To Animate a Character You've Never Seen Before, including an mp3 recording and slides. The lecture is much less technical than this paper; it's only an hour and gives a very high level overview.

Frequently Asked Questions

Why are there no frequently asked questions?

Because I haven't even hit submit on this page yet. But, if you're reading this, that means I finally did, and you should ask some.