Tangent-space optimization for interactive animation control

Abstract

Character animation tools are based on a keyframing metaphor where artists pose characters at selected keyframes and the software automatically interpolates the frames inbetween. Although the quality of the interpolation is critical for achieving a fluid and engaging animation, the tools available to adjust the result of the automatic inbetweening are rudimentary and typically require manual editing of spline parameters. As a result, artists spend a tremendous amount of time posing and setting more keyframes. In this pose-centric workflow, animators use combinations of forward and inverse kinematics. While forward kinematics leads to intuitive interpolations, it does not naturally support positional constraints such as fixed contact points. Inverse kinematics can be used to fix certain points in space at keyframes, but can lead to inferior interpolations, is slow to compute, and does not allow for positional contraints at non-keyframe frames. In this paper, we address these problems by formulating the control of interpolations with positional constraints over time as a space-time optimization problem in the tangent space of the animation curves driving the controls. Our method has the key properties that it (1) allows the manipulation of positions and orientations over time, extending inverse kinematics, (2) does not add new keyframes that might conflict with an artist's preferred keyframe style, and (3) works in the space of artist editable animation curves and hence integrates seamlessly with current pipelines. We demonstrate the utility of the technique in practice via various examples and use cases.

References

1. Andreas Aristidou, Joan Lasenby, Yiorgos Chrysanthou, and Ariel Shamir. 2018. Inverse Kinematics Techniques in Computer Graphics: A Survey. Computer Graphics Forum 37, 6 (2018), 35--58.
2. Autodesk. 2018. Maya.
3. Jinxiang Chai and Jessica K. Hodgins. 2007. Constraint-based Motion Optimization Using a Statistical Dynamic Model. ACM Trans. Graph. 26, 3 (2007).
4. Byungkuk Choi, Roger B. i Ribera, J. P. Lewis, Yeongho Seol, Seokpyo Hong, Haegwang Eom, Sunjin Jung, and Junyong Noh. 2016. SketchiMo: Sketch-based Motion Editing for Articulated Characters. ACM Trans. Graph. 35, 4 (2016), 146:1--146:12.
5. Myung G. Choi and Kang H. Lee. 2016. Points-based user interface for character posing. Computer Animation and Virtual Worlds 27, 3--4 (2016), 213--220.
6. Loïc Ciccone, Martin Guay, Maurizio Nitti, and Robert W. Sumner. 2017. Authoring Motion Cycles. In Proceedings of the 16th ACM SIGGRAPH/Eurographics Symposium on Computer Animation. 8:1--8:9.
7. Michael F. Cohen. 1992. Interactive Spacetime Control for Animation. In Proceedings of the 19th Annual Conference on Computer Graphics and Interactive Techniques. 293--302.
8. Oliver Glauser, Wan-Chun Ma, Daniele Panozzo, Alec Jacobson, Otmar Hilliges, and Olga Sorkine-Hornung. 2016. Rig Animation with a Tangible and Modular Input Device. ACM Trans. Graph. 35, 4 (2016), 144:1--144:11.
9. Michael Gleicher. 1997. Motion Editing with Spacetime Constraints. In Proceedings of the 1997 Symposium on Interactive 3D Graphics. 139--ff.
10. Michael Gleicher and Andrew P. Witkin. 1991. Differential Manipulation. In Proceedings of Graphics Interface.
11. Martin Guay, Marie-Paule Cani, and Rémi Ronfard. 2013. The Line of Action: An Intuitive Interface for Expressive Character Posing. ACM Trans. Graph. 32, 6 (2013), 205:1--205:8.
12. Martin Guay, Rémi Ronfard, Michael Gleicher, and Marie-Paule Cani. 2015. Space-time Sketching of Character Animation. ACM Trans. Graph. 34, 4 (2015), 118:1--118:10.
13. Fabian Hahn, Frederik Mutzel, Stelian Coros, Bernhard Thomaszewski, Maurizio Nitti, Markus Gross, and Robert W. Sumner. 2015. Sketch Abstractions for Character Posing. In Proc. of the 14th ACM SIGGRAPH/Eurographics Symposium on Computer Animation. 185--191.
14. Félix G. Harvey and Christopher Pal. 2018. Recurrent Transition Networks for Character Locomotion. In SIGGRAPH Asia 2018 Technical Briefs. 4:1--4:4.
15. Ollie Johnston and Frank Thomas. 1981. The illusion of life: Disney animation. Disney Editions New York.
16. Yuki Koyama and Masataka Goto. 2018. OptiMo: Optimization-Guided Motion Editing for Keyframe Character Animation. In Proceedings of the 2018 CHI Conference on Human Factors in Computing Systems. 161:1--161:12.
17. Mikko Kytö, Krupakar Dhinakaran, Aki Martikainen, and Perttu Hämäläinen. 2017. Improving 3D Character Posing with a Gestural Interface. IEEE Computer Graphics and Applications 37, 1 (2017), 70--78.
18. Andreas M. Lehrmann, Peter V. Gehler, and Sebastian Nowozin. 2014. Efficient Nonlinear Markov Models for Human Motion. In 2014 IEEE Conference on Computer Vision and Pattern Recognition. 1314--1321.
19. Jianyuan Min, Yen-Lin Chen, and Jinxiang Chai. 2009. Interactive Generation of Human Animation with Deformable Motion Models. ACM Trans. Graph. 29, 1 (2009), 9:1--9:12.
20. APS Mosek. 2010. The MOSEK optimization software. Online at http://www.mosek.com 54, 2--1 (2010).
21. Jean-Christophe Nebel. 1999. Keyframe interpolation with self-collision avoidance. In Computer Animation and Simulation '99. 77--86.
22. A. Cengiz Öztireli, Ilya Baran, Tiberiu Popa, Boris Dalstein, Robert W. Sumner, and Markus Gross. 2013. Differential Blending for Expressive Sketch-based Posing. In Proc. of the 12th ACM SIGGRAPH/Eurographics Symposium on Computer Animation. 155--164.
23. Charles Rose, Brian Guenter, Bobby Bodenheimer, and Michael F. Cohen. 1996. Efficient Generation of Motion Transitions Using Spacetime Constraints. In Proceedings of the 23rd Annual Conference on Computer Graphics and Interactive Techniques. 147--154.
24. Xiaohan Shi, Kun Zhou, Yiying Tong, Mathieu Desbrun, Hujun Bao, and Baining Guo. 2007. Mesh Puppetry: Cascading Optimization of Mesh Deformation with Inverse Kinematics. ACM Trans. Graph. 26, 3 (2007), 81--89.
25. Jack M. Wang, David J. Fleet, and Aaron Hertzmann. 2008. Gaussian Process Dynamical Models for Human Motion. IEEE Transactions on Pattern Analysis and Machine Intelligence 30, 2 (2008), 283--298.
26. Xiaolin Wei and Jinxiang Chai. 2011. Intuitive Interactive Human-Character Posing with Millions of Example Poses. IEEE Computer Graphics and Applications 31, 4 (2011), 78--88.
27. Harold Whitaker and John Halas. 2013. Timing for animation. CRC Press.
28. Andrew Witkin and Michael Kass. 1988. Spacetime Constraints. In Proceedings of the 15th Annual Conference on Computer Graphics and Interactive Techniques. 159--168.
29. Katsu Yamane and Yoshihiko Nakamura. 2003. Natural Motion Animation through Constraining and Deconstraining at Will. IEEE Transactions on Visualization and Computer Graphics 9, 3 (2003), 352--360.
30. Wataru Yoshizaki, Yuta Sugiura, Albert C. Chiou, Sunao Hashimoto, Masahiko Inami, Takeo Igarashi, Yoshiaki Akazawa, Katsuaki Kawachi, Satoshi Kagami, and Masaaki Mochimaru. 2011. An Actuated Physical Puppet As an Input Device for Controlling a Digital Manikin. In Proceedings of the SIGCHI Conference on Human Factors in Computing Systems. 637--646.
31. Xinyi Zhang and Michiel van de Panne. 2018. Data-driven Autocompletion for Keyframe Animation. In MIG'18: Motion, Interaction and Games (MIG 2018). 1--11.

Index Terms

• Computing methodologies

  • Computer graphics

    • Animation

    • Graphics systems and interfaces