A hybrid iterative solver for robustly capturing coulomb friction in hair dynamics

DavietGilles,; Bertails-DescoubesFlorence,; BoissieuxLaurence,

doi:10.1145/2070781.2024173

Cited by 80 publications

(40 citation statements)

References 44 publications

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“…Such simulations were for long limited in complexity and resolution due to computational overhead. Recently, some authors demonstrated that the simulation of thousands guide strands subject to complex hair-body and hair-hair interactions was now affordable on a standard desktop computer [Selle et al 2008;McAdams et al 2009;Daviet et al 2011].…”

Section: Related Workmentioning

confidence: 99%

“…This format indeed corresponds to the standard output produced by hair designing tools and recent hair capture systems. Furthermore, representing hair with curves is in line with the input of the most advanced hair animation systems, which often simulate a discrete assembly of guide strands [Hadap 2006;Selle et al 2008;McAdams et al 2009;Bergou et al 2010;Daviet et al 2011].…”

Section: D Geometric Fittingmentioning

confidence: 99%

“…The nonsmooth equations of motion for a Lagrangian dynamical system subject to contact forces and exact Coulomb friction (see, e.g., [Acary and Brogliato 2008] for a comprehensive introduction) were introduced to Computer Graphics in Daviet et al 2011], and are briefly reminded here to the reader. In the absence of contact forces, the dynamics of the system is described as a smooth differential equation,…”

Section: Direct Dynamic Problem With Contactsmentioning

confidence: 99%

“…where W is a symmetric positive (semi-)definite matrix of size (3 n, 3 n), and c a vector of size 3 n. In the direct (dynamic) case, W was identified to the sparse (discrete) Delassus operator Daviet et al 2011]. In our static inversion problem, W is identified to our W matrix, which is sparse, symmetric and positive-definite.…”

Section: An Efficient and Robust Socqp Solvermentioning

confidence: 99%

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Inverse dynamic hair modeling with frictional contact

et al. 2013

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Figure 1: Our inversion method makes the hair synthesis pipeline consistent: (a) Raw hair geometry (a set of polylines) resulting from the manual design or the automatic capture of a static hairstyle (here, a capture from [Herrera et al. 2012]); (b) Input geometry is automatically converted into a dynamic hair model (a set of super-helices) at equilibrium under gravity and frictional hair-body and hair-hair contact forces; Unlike classical hair simulators (c) which ignore surrounding forces when initializing the hairstyle and are thus prone to undesired sagging, our simulator (b) exactly matches the original hair geometry at initial state and (d) yields a realistic, character-specific hair animation. AbstractIn the latest years, considerable progress has been achieved for accurately acquiring the geometry of human hair, thus largely improving the realism of virtual characters. In parallel, rich physics-based simulators have been successfully designed to capture the intricate dynamics of hair due to contact and friction. However, at the moment there exists no consistent pipeline for converting a given hair geometry into a realistic physics-based hair model. Current approaches simply initialize the hair simulator with the input geometry in the absence of external forces. This results in an undesired sagging effect when the dynamic simulation is started, which basically ruins all the efforts put into the accurate design and/or capture of the input hairstyle. In this paper we propose the first method which consistently and robustly accounts for surrounding forcesgravity and frictional contacts, including hair self-contacts -when converting a geometric hairstyle into a physics-based hair model. Taking an arbitrary hair geometry as input together with a corresponding body mesh, we interpret the hair shape as a static equilibrium configuration of a hair simulator, in the presence of gravity as well as hair-body and hair-hair frictional contacts. Assuming that hair parameters are homogeneous and lie in a plausible range of physical values, we show that this large underdetermined inverse problem can be formulated as a well-posed constrained optimization problem, which can be solved robustly and efficiently by leveraging the frictional contact solver of the direct hair simulator. Our method was successfully applied to the animation of various hair geometries, ranging from synthetic hairstyles manually designed by an artist to the most recent human hair data automatically reconstructed from capture.

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Section: Related Workmentioning

confidence: 99%

Section: D Geometric Fittingmentioning

confidence: 99%

Section: Direct Dynamic Problem With Contactsmentioning

confidence: 99%

Section: An Efficient and Robust Socqp Solvermentioning

confidence: 99%

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Inverse dynamic hair modeling with frictional contact

et al. 2013

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“…More recently, hair-body and hair-hair contacts have been more accurately modeled by using a non-smooth Newton solver for the Coulomb friction law . Daviet et al [2011] globally solves for Coulomb friction with a hybrid Gauss-Seidel algorithm, using an analytic solver to ensure convergence.…”

Section: Related Workmentioning

confidence: 99%

Artistic simulation of curly hair

Iben¹,

Meyer²,

Petrović³

et al. 2013

Proceedings of the 12th ACM SIGGRAPH/Eurographics Symposium on Computer Animation

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We present a novel method for stably simulating stylized curly hair that addresses artistic needs and performance demands, both found in the production of feature films. To satisfy the artistic requirement of maintaining the curl's helical shape during motion, we propose a hair model based upon an extensible elastic rod. We introduce a novel method for stably computing a frame along the hair curve, essential for stable simulation of curly hair. Our hair model introduces a novel spring for controlling the bending of the curl and another for maintaining the helical shape during extension. We also address performance concerns often associated with handling hairhair contact interactions by efficiently parallelizing the simulation. To do so, we present a novel algorithm for pruning both hair-hair contact pairs and hair particles. Our method is in use on a full length feature film and has proven to be robust and stable over a wide range of animated motion and on a variety of hair styles, from straight to wavy to curly.

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A nonsmooth method for spatial frictional contact dynamics of flexible multibody systems with large deformation

Wang

Tian

2022

Numerical Meth Engineering

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A nonsmooth contact dynamics computation methodology for spatial frictional contact dynamics of flexible multibody systems with large deformation is presented. The contact and friction conditions between contact bodies are formulated as a cone complementary problem (CCP). Based on the mortar discretization method, nonsmooth frictional contact formulations for surface‐to‐surface and beam‐to‐beam contact problems are derived. These formulations can be used to study a wide range of contact problems between three‐dimensional bodies, thin plates and beams. The nonsmooth multibody dynamics equations are solved by using the generalized‐α$$ \alpha $$ method. The CCP is solved by using the accelerated projected gradient descend (APGD) algorithm in each Newton's iteration. Finally, six numerical examples are provided to validate the proposed computation methodology.

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A hybrid iterative solver for robustly capturing coulomb friction in hair dynamics

Cited by 80 publications

References 44 publications

Inverse dynamic hair modeling with frictional contact

Inverse dynamic hair modeling with frictional contact

Artistic simulation of curly hair

A nonsmooth method for spatial frictional contact dynamics of flexible multibody systems with large deformation

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