Realtime Performance‐Driven Physical Simulation for Facial Animation

Barrielle, Vincent; Stoiber, Nicolas

doi:10.1111/cgf.13450

Cited by 13 publications

(8 citation statements)

References 55 publications

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“…Li et al presented a system to combine arbitrary triangle mesh animations with physically based Finite Element Method (FEM) simulation, enabling control both in space and time [LXB17]. Researchers also added physics to facial animation, by forming facial blendshapes as a basis of forces [BSC16], using the original animation as per‐frame rest poses [KBB*17], or augmenting real‐time performance capture with physics [BS19]. Researchers at Pixar, focusing on providing state‐of‐the‐art nonlinear elasticity models (we use their neo‐Hookean material [SGK18] in our work), also demonstrated how to effectively use constraints to add secondary soft‐tissue dynamics [SGK18, SGK19, KDGI19].…”

Section: Related Workmentioning

confidence: 99%

Adjustable Constrained Soft‐Tissue Dynamics

Wang

Zheng

Barbič

2020

Computer Graphics Forum

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Physically based simulation is often combined with geometric mesh animation to add realistic soft-body dynamics to virtual characters. This is commonly done using constraint-based simulation whereby a soft-tissue simulation is constrained to geometric animation of a subpart (or otherwise proxy representation) of the character. We observe that standard constraint-based simulation suffers from an important flaw that limits the expressiveness of soft-body dynamics. Namely, under correct physics, the frequency and amplitude of soft-tissue dynamics arising from constraints ("inertial amplitude") are coupled, and cannot be adjusted independently merely by adjusting the material properties of the model. This means that the space of physically based simulations is inherently limited and cannot capture all effects typically expected by computer animators. For example, animators need the ability to adjust the frequency, inertial amplitude, gravity sag and damping properties of the virtual character, independently from each other, as these are the primary visual characteristics of the soft-tissue dynamics. We demonstrate that independence can be achieved by transforming the equations of motion into a non-inertial reference coordinate frame, then scaling the resulting inertial forces, and then converting the equations of motion back to the inertial frame. Such scaling of inertia makes it possible for the animator to set the character's inertial amplitude independently from frequency. We also provide exact controls for the amount of character's gravity sag, and the damping properties. In our examples, we use linear blend skinning and pose-space deformation for geometric mesh animation, and the Finite Element Method for soft-body constrained simulation; but our idea of scaling inertial forces is general and applicable to other animation and simulation methods. We demonstrate our technique on several character examples. CCS Concepts • Computing methodologies → Physical simulation;

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Section: Related Workmentioning

confidence: 99%

Adjustable Constrained Soft‐Tissue Dynamics

Wang

Zheng

Barbič

2020

Computer Graphics Forum

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“…Such a method has been applied in the field of simulation and animation to solve various approximation problems. To generate real-time facial animations, Barrielle et al [66] applied first-order Taylor approximation to the computations of the Singular Value Decomposition, thereby significantly accelerating the simulation of volumetric forces. Shen et al [67] adopted a finite Taylor series approximation of the potential energy to avoid numerical singularity and instability during the simulation of inextensible ribbon.…”

Section: Related Workmentioning

confidence: 99%

Example-based Real-time Clothing Synthesis for Virtual Agents

Wu,

Chao,

Chen

et al. 2021

Preprint

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We present a real-time cloth animation method for dressing virtual humans of various shapes and poses. Our approach formulates the clothing deformation as a high-dimensional function of body shape parameters and pose parameters. In order to accelerate the computation, our formulation factorizes the clothing deformation into two independent components: the deformation introduced by body pose variation (Clothing Pose Model) and the deformation from body shape variation (Clothing Shape Model). Furthermore, we sample and cluster the poses spanning the entire pose space and use those clusters to efficiently calculate the anchoring points. We also introduce a sensitivity-based distance measurement to both find nearby anchoring points and evaluate their contributions to the final animation. Given a query shape and pose of the virtual agent, we synthesize the resulting clothing deformation by blending the Taylor expansion results of nearby anchoring points. Compared to previous methods, our approach is general and able to add the shape dimension to any clothing pose model. Furthermore, we can animate clothing represented with tens of thousands of vertices at 50+ FPS on a CPU. We also conduct a user evaluation and show that our method can improve a user's perception of dressed virtual agents in an immersive virtual environment compared to a conventional linear blend skinning method.

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“…They were briefly demonstrated as an example of more general work on adhesion by Gascón et al [18], but they did no consider accurately modelling the lips or the way they stick. Barrielle and Stoiber used spring based constraints to model sticky lips [19]. In contrast to Barrielle and Stoiber's work, our finite element method approach produces more physically realistic sticky lip behaviours, such as the continuous "zippering" as the mouth opens.…”

Section: Related Workmentioning

confidence: 99%

“…These distances show a quantitative improvement in the behaviour of the model when stickiness is included. [19], where the mouth opens twice. The graph was generated from a portion of the video accompanying their paper [19].…”

Section: Opening Over Timementioning

confidence: 99%

See 1 more Smart Citation

An Evaluation Approach for a Physically-Based Sticky Lip Model †

Leach

Maddock

2019

Computers

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Physically-based mouth models operate on the principle that a better mouth animation will be produced by simulating physically accurate behaviour of the mouth. In the development of these models, it is useful to have an evaluation approach which can be used to judge the effectiveness of a model and draw comparisons against other models and real-life mouth behaviour. This article presents a set of metrics which can be used to describe the motion of the lips, as well as a process for measuring these from video of real or simulated mouths, implemented using Python and OpenCV. As an example, the process is used to evaluate a physically-based mouth model focusing on recreating the stickiness effect of saliva between the lips. The metrics highlight the changes in behaviour due to the addition of stickiness between the lips in the synthetic mouth model and show quantitatively improved behaviour in relation to real mouth movements. The article concludes that the presented metrics provide a useful approach for evaluation of mouth animation models that incorporate sticky lip effects.

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Realtime Performance‐Driven Physical Simulation for Facial Animation

Cited by 13 publications

References 55 publications

Adjustable Constrained Soft‐Tissue Dynamics

Adjustable Constrained Soft‐Tissue Dynamics

Example-based Real-time Clothing Synthesis for Virtual Agents

An Evaluation Approach for a Physically-Based Sticky Lip Model †

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