Active volumetric musculoskeletal systems

Abstract

Figure 1: Our framework spans the entire pipeline for simulating volumetric musculoskeletal systems, starting from data on the active shapes of muscles to physically based simulation of muscles and soft tissues coupled to the skeletal system. (a) MRI 1 of the eye can reveal both passive and active muscle shapes. (b) Reconstructed muscle shapes. (c) Physically based simulation of an individual's eye movement using our system. (d) Upper arm with six muscles and a bone in close sliding contact with each other. Volume preservation produces realistic lateral bulging. (e) Dynamic simulation of arm with soft tissues, a soft glove, and contact with the environment. AbstractWe introduce a new framework for simulating the dynamics of musculoskeletal systems, with volumetric muscles in close contact and a novel data-driven muscle activation model. Muscles are simulated using an Eulerian-on-Lagrangian discretization that handles volume preservation, large deformation, and close contact between adjacent tissues. Volume preservation is crucial for accurately capturing the dynamics of muscles and other biological tissues. We show how to couple the dynamics of soft tissues with Lagrangian multibody dynamics simulators, which are widely available. Our physiologically based muscle activation model utilizes knowledge of the active shapes of muscles, which can be easily obtained from medical imaging data or designed to meet artistic needs. We demonstrate results with models derived from MRI data and models designed for artistic effect.

Dynamic skin deformation simulation using musculoskeletal model and soft tissue dynamics

“…The muscle shape has been approximated using ellipsoids [12], or learned from anatomical data as in BodyParts3D [13]. Deformation of muscles and soft tissues is often simulated by physics-based models such as mass-spring-damper models [14] and volumetric models such as the finite element method [15][16][17] or the finite volume method [18].…”

Biomechanical simulation and control of hands and tendinous systems

“…More importantly for hand simulation, handling of routing constraints, including branching and kinematic loops, is difficult with these methods. Simulators based on solid mechanics models, such as spline volumes [Ng-Thow-Hing 2001], finite volume method [Teran et al 2003;Teran et al 2005], finite element method, [Chen and Zeltzer 1992;Zhu et al 1998;Sifakis et al 2005;Blemker and Delp 2005;Kaufman et al 2010], or even Eulerian solids [Fan et al 2014] are also not ideal for hand simulation, since the musculotendons of the hand are thin and anisotropic, and would require many disproportionately small elements. Various dynamic models [Spillmann and Teschner 2008;Bergou et al 2008;Bergou et al 2010] from the computer graphics community could potentially be used for musculotendon simulation, but these models were designed for use in free-floating configurations, and do not work well in the highly-constraining situations present in the hand.…”

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

“…These methods are very much in line with the spirit of our work but are, again, limited to particular instances of MHMMs (rigid modes and deformable superquadrics, poking functions adding details over modal models). Finally, the Eulerian-on-Lagrangian method [Fan et al 2013;Fan et al 2014] allows the coupling of a fine scale Eulerian simulation to any coarse scale Lagrangian simulation. The method is general but limited to Eulerian-Lagrangian coupling.…”

“…The method is general but limited to Eulerian-Lagrangian coupling. Additionally the Eulerian simulation must cover entire deformable objects, meaning that detail cannot be added locally thus negating any potential performance gains (i.e in Fan et al [2014] entire groups of muscles are covered with simulation grids rather than one muscle being covered by many grids) . Conversely, the focus of MHMMs is to provide a principled, controllable, layered methodology for adding local detail to coarser simulations, something that none of the previous work in this area provide.…”