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Abstract
Creating facial animations using 3D computer graphics represents a very laborious and time-consuming task. Among the numberless approaches for animating faces, the use of blendshapes remains the most common solution because of their simplicity and the ability to produce high-quality results. This approach, however, is also characterized by important drawbacks. With the traditional animation suites, to select the blendshapes to be activated animators are generally requested to memorize the mapping between the blendshapes and the influenced mesh vertices; alternatively, they need to adopt a trial-and-error search within the whole library of available blendshapes. Moreover, the level of expressiveness that can be reached may be lower than expected; this is due to the fact that the possibility to apply transformations to vertices different than just linear translations and mechanisms for adding, e.g., exaggerations, are typically not integrated into the same animation environment. To tackle these issues, this article proposes an immersive virtual reality-based interface that leverages sketches for the direct manipulation of blendshapes. Animators can draw both linear and curved strokes, which are used to automatically extract information about the blendshape to be activated and its weight, the trajectories that associated vertices have to follow, as well as the timing of the overall animation. A user study was carried out with the aim of evaluating the proposed approach on several representative animations tasks. Both objective and subjective measurements were collected. Experimental results showed the benefits of the devised interface in terms of task completion time, animation accuracy, and usability.
Acknowledgments
This work was mainly developed at the VR@POLITO, the Virtual Reality lab of Politecnico di Torino. The authors want to thank the Logitech Design Lab for providing them with a VR Ink Pilot Edition stylus.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Notes
2 AnimVR: https://nvrmind.io/
3 Facebook Quill: https://quill.fb.com/
4 Tvori: https://tvori.co/
5 Masterpiece VR: https://masterpiecestudio.com/
6 Blender: https://www.blender.org/
8 Unreal Engine: https://docs.unrealengine.com/5.0/en-US/fbx-morph-target-pipeline-in-unreal-engine/
9 VRChat: https://hello.vrchat.com/
10 HTC Vive: https://www.vive.com
11 Virtual Reality Viewport: https://github.com/dfelinto/
Additional information
Funding
Notes on contributors
Alberto Cannavò
Alberto Cannavò received his PhD degree in computer engineering from Politecnico di Torino, Italy, in 2020. He is currently an Assistant Professor with time contract at the Dipartimento di Automatica e Informatica of Politecnico di Torino. His fields of interest include computer graphics and human-machine interaction.
Emanuele Stellini
Emanuele Stellini received his Master Thesis degree in computer engineering from Politencico di Torino, Italy, in 2021. His fields of interest include computer graphics and computer animation.
Congyi Zhang
Congyi Zhang received his Ph.D. degree from the School of Electronics Engineering and Computer Science, Peking University, in 2019. He is currently a postdoctoral fellow at the University of Hong Kong. His fields of interest include 3D reconstruction and modeling, augmented reality and virtual reality, and human–computer interaction.
Fabrizio Lamberti
Fabrizio Lamberti received his Ph.D. degrees in computer engineering from Politecnico di Torino, Italy, in 2005. He is currently a Full Professor at the Dipartimento di Automatica e Informatica at Politecnico di Torino. His fields of interest include computer graphics, human-machine interaction, and intelligent computing.