Physics-Based Character Skinning Using Multidomain Subspace Deformations

Kim, T.; James, Doug L.

doi:10.1109/tvcg.2012.78

Cited by 26 publications

(5 citation statements)

References 57 publications

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“…In [CBC*05], characters were animated using force‐driven rigs, with the forces described using the rig building blocks. One can also construct a deformation basis from a skeleton embedded into a tetrahedral mesh, and combine it with domain‐decomposition to simulate articulated deformable characters [KJ12]. Piovarči et al created a physically‐inspired stretching model to evaluate the stretching caused by the gravitational force or muscle contractions [PMĎ15].…”

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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“…Direct connections with the Schur complement method and block-decomposed iterative solvers for linear algebra are then easily established for faster solves. These methods o er exciting opportunities for scalable performance that have also been applied in graphics [Huang et al 2006;Kim and James 2012;Liu et al 2016;Sellán et al 2018], but can also su er from slower convergence or gapping between imperfectly joined interfaces [Kim and James 2012]. Domain decompositions, including the classic Schwartz methods, have also been extended to the nonlinear regime [Dolean et al 2015;Xiao-Chuan and Maksymilian 1994].…”

Section: Related Workmentioning

confidence: 99%

Decomposed optimization time integrator for large-step elastodynamics

Gao

Langlois

et al. 2019

ACM Trans. Graph.

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time step, nonlinear problems of implicit numerical time integration. DOT is especially suitable for large time step simulations of deformable bodies with nonlinear materials and high-speed dynamics. It is e cient, automated, and robust at large, xed-size time steps, thus ensuring stable, continued progress of high-quality simulation output. Across a broad range of extreme and mild deformation dynamics, using frame-rate size time steps with widely varying object shapes and mesh resolutions, we show that DOT always converges to user-set tolerances, generally well-exceeding and always close to the best wall-clock times across all previous nonlinear time step solvers, irrespective of the deformation applied.

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“…Furthermore, there are complications when allowing the detail level to be fully dynamic. Other methods based on substructuring are also commonly applied in engineering and graphics [Barbič and Zhao 2011;Kim and James 2012]. Often per-component reduced models are used to improve performance.…”

Section: Related Workmentioning

confidence: 99%

Multifarious hierarchies of mechanical models for artist assigned levels-of-detail

Malgat

Gilles

Levin

et al. 2015

Proceedings of the 14th ACM SIGGRAPH / Eurographics Symposium on Computer Animation

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a) Coarse framebased simulation (b) Fine FEM simulation (c) Mixing a coarse frame-based simulation to a local FEM patch with our method Figure 1: Using a hook to catch a coarsely discretized frame-based octopus is challenging due to the lack of deformation at the contact point (1a). One could resolve this problem with a high-resolution set of finite elements (1b) but, at the expense of runtime performance and with the introduction of spurious secondary motion. Multifarious Hierarchies of Mechanical Models allow an artist to add arbitrarily located detail simulations to the underlying coarse deformation models in order to produce the desired result. (1c). AbstractWe present a new framework for artist driven level of detail in solid simulations. Simulated objects are simultaneously embedded in several, separately designed deformation models with their own independent degrees of freedom. The models are ordered to apply their deformations hierarchically, and we enforce the uniqueness of the dynamics solutions using a novel kinetic filtering operator designed to ensure that each child only adds detail motion to its parent without introducing redundancies. This new approach allows artists to easily add fine-scale details without introducing unnecessary degrees-of-freedom to the simulation or resorting to complex geometric operations like anisotropic volume meshing. We illustrate the utility of our approach with several detail enriched simulation examples.

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Physics-Based Character Skinning Using Multidomain Subspace Deformations

Cited by 26 publications

References 57 publications

Adjustable Constrained Soft‐Tissue Dynamics

Adjustable Constrained Soft‐Tissue Dynamics

Decomposed optimization time integrator for large-step elastodynamics

Multifarious hierarchies of mechanical models for artist assigned levels-of-detail

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