A. Witkin and W. Welch. Fast Animation and Control of Nonrigid Structures. Computer Graphics: SIGGRAPH'90 Conference Proceedings, Aug., 1990, pp. 243-252. Pointers in Constraint Models - i -  Home/Search   Document Details and Download   Summary   Related Articles   Check

....by the user. The issue then becomes that of how to implement the constraints required by such an articulated system. The topic of spacetime constraints has been of particular interest in addressing this issue, and has been researched quite extensively [Witkin et al. 1987, Witkin and Kass, 1988, Witkin and Welch, 1990, Cohen 1992, Ngo and Marks, 1993, Rose et al. 1996] Throughout this thesis we are primarily concerned with kinematics based approaches to skeletal animation, and thus do not cover in detail the issues involved with dynamics modelling of articulated structures. We do, however, investigate a ....

Witkin, A. and Welch, W. (1990). Fast animation and control of nonrigid structures. In Proceedings of the 17th annual conference on Computer graphics and interactive techniques, pages 243---252. ACM Press.

....[33] Following their introduction, physically based deformations were extended in many ways. Platt and Barr [24] introduced better constraint handling via Lagrange multipliers. Pentland and Williams [23] obtained realtime simulations by using only a few vibration modes. Witkin and Welch [35] introduced the use of loworder polynomial deformations to achieve fast deformations. Baraff and Witkin [1] added non penetration constraints to this framework. Metaxas and Terzopoulos [21] combined global deformations with local finite element deformations. Implicit solvers are enjoying a ....

Andrew Witkin and William Welch. Fast animation and control of nonrigid structures. Computer Graphics (Proceedings of SIGGRAPH 90), 24(4):243--252, August 1990. ISBN 0-201-50933-4. Held in Dallas, Texas.

....variation in our experiment (see Fig. 3) but results depend on the material parameters chosen and the type of experiment conducted. In applications where these volume variations are considered too high, volume preservation could be enforced directly as a hard constraint like in Witkin s work [20, 19]. 4 Application to Hexahedral Meshes The use of hexahedral meshes is not as common as tetrahedral ones, since the geometry they can define is more limited. However, these meshes may be useful for animating objects modeled using voxels [2] This kind of data, with information about material ....

A. Witkin and W. Welch. Fast animation and control of nonrigid structures. In SIGGRAPH '90 Conference Proceedings, pages 243--252. Addison Wesley, Aug. 1990.

.... 57] A survey of deformable modeling in computer graphics can be found in [22] The use of physical simulation and related optimization techniques as a means of geometric interaction has been applied to animation [58] drawing [59] free form surface and volume modeling [15] mechanical design [65], and interactive molecular simulation [55] For a discussion on the dynamic simulation of nonpenetrating flexible bodies see [6] Models and algorithms appropriate for the collision of deformable bodies are investigated in [19] 4 An Algorithm for Planning Paths for Elastic Objects Under ....

A. Witkin and W. Welch. Fast animation and control of non-rigid structures. Computer Graphics (SIGGRAPH'90), pages 243-252, 1990.

....shapes. This paper describes a method for knot tying with simulated rope. The rope is a physically based dynamics simulation [15] Our experiments consist of pulling a loosely knotted rope configuration tight and witnessing that the knot was maintained. Our rope is a spline of linear springs [17]. The topology of the rope varies adaptively to maintain the surface of the rope. Self intersections in the rope are discrete event simulated using the impulse model of collision [8] in the interpolation step of the physical simulation. During the adaptive reparametriza Figure 1: Illustration of ....

A. Witkin and W. Welch. Fast animation and control of nonrigid structures. Computer Graphics (SIGGRAPH'90), pages 243-- 252, 1990.

.... In graphics physically based models have been proposed for deformable parts [19, 20] The use of physical simulation and related optimization techniques as a means of geometric interaction has been applied to animation [21] free form surface and volume modeling [4] and mechanical design [23]. For a discussion on the dynamic simulation of non penetrating flexible bodies see [1] 3 f PRM: General Description f PRM repeats a basic step until a query is answered or until an predefined amount of time has elapsed. The method can be seen as a single shot method (answering a single user ....

A. Witkin and W. Welch. Fast animation and control of non-rigid structures. Computer Graphics (SIGGRAPH '90), pages 243-252, 1990.

....Other approaches have been taken to animate deformable objects of fixed topology. Elasticity and visco elasticity have been modeled with success [7, 25, 27, 26] but these methods suffer from the same time step handicap. Global methods, gaining efficiency by restricting the possible deformations [21, 31], are perfect for interactive manipulation, but, unfortunately, offer limited realism. To the authors knowledge, only few existing approaches achieve real time computations for deformable structured objects. The first is derived from finite element theory, and takes advantage of linear ....

A. Witkin and W. Welch. Fast animation and control for non-rigid structures. Computer Graphics, 24(4):243--252, Aug. 1990.

....reef knot This paper describes a method for knot tying with simulated rope. The rope is a physically based dy namics simulation [14] Our experiments consist of pulling a loosely knotted rope configuration tight and witnessing that the knot was maintained. Our rope is a spline of linear springs [15]. The topol ogy of the rope varies adaptively to maintain the surface of the rope. Self intersections in the rope are discrete event simulated using the impulse model of collision [8] in the interpolation step of the physical simulation. During the adaptive reparametrization of the rope, some ....

A. Witkin and W. Welch. Fast animation and control of non-rigid structures. Computer Graphics (SIGGRAPH '90), pages 243-252, 1990.

....DyRT to objects, with a particular emphasis on bone based character animation. 1.1 Related Work Significant work has been done on simulating dynamic deformable objects, in areas such as human body modeling and interactive simulation. Despite the large amount of pioneering work on deformation [25, 28, 15, 1], there continue to be exciting new applications [18, 17] and improvements in simulation e#ciency [2, 6] Numerous examples of human body modeling exist in the literature with particular areas of interest being deformations of skin and muscles [27, 9] faces [12] and layered models [5] Support ....

....interest for graphics hardware are datadriven deformation models based on linear superposition of precomputable global deformation bases [3] which include space warping methods such as FFD. While such models can provide fast simulation and constraint handling for physically based dynamic [19, 28] and also static [11, 10] deformable models, we are primarily interested in their amenability to graphics hardware simulation [14] For simulating free vibrations of elastic models with modest amplitudes, global deformation bases based on Karhunen Loeve expansions from modal analysis provide the ....

A. Witkin and W. Welch. Fast Animation and Control of Nonrigid Structures. In Computer Graphics (SIGGRAPH 90 Conference Proceedings), pages 243-- 252, 1990.

....Other approaches have been taken to animate deformable objects of fixed topology. Elasticity and visco elasticity have been modeled with success [5, 8, 9, 10] but these methods suffer from the same time step handicap. Global methods, gaining efficiency by restricting the possible deformations [11, 12], are useful for interactive manipulation, but, unfortunately, offer limited realism. To the authors knowledge, only a few existing approaches achieve real time computations for deformable structured objects. The first is derived from finite element theory, and takes advantage of linear ....

Andrew Witkin and William Welch. Fast animation and control for non-rigid structures. Computer Graphics, 24(4):243--252, August

....the global shape parameters of a conventional superquadric with the local degrees of freedom of a spline. In [7] deformable objects are animated using spring mass models and wind fields. Several techniques using implicit models have been proposed as a means to model dynamic deformations. In [8], polynomial global deformations are used in a physicsbased model. The set of allowed deformations are all those expressible as a linear transformation of the state parameters. Our work makes use of a somewhat similar idea as a point of departure. The control method used in [8] is based on ....

....deformations. In [8] polynomial global deformations are used in a physicsbased model. The set of allowed deformations are all those expressible as a linear transformation of the state parameters. Our work makes use of a somewhat similar idea as a point of departure. The control method used in [8] is based on following motion paths. In [9] global implicit deformations are used in conjunction with physics basedsimulation for the animation of polygonal and parametric objects. This formulation is 6 similar to the one presented in [8] uses deformations that are linear with respect to the ....

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A. Witkin and W. Welch, "Fast animation and control of nonrigid structures," Proceedings of ACM SIGGRAPH: Computer Graphics, vol. 24, no. 4, pp. 243--252, August 1990.

....alternate approaches have been derived, allowing fast animation of simple dynamic objects by taking into account only some possible deformations or vi # iMAGIS GRAVIR is a joint project of CNRS, INRIA, Institut National Polytechnique de Grenoble and Universite Joseph Fourier. bration modes [21, 26, 19]. Unfortunately, such restrictions on the behavior considerably affects the realism of the animation. Other approaches developed robust implicit integration schemes to allow for larger time steps, thus dramatically reducing the necessary computational time per second of animation [1, 11] As ....

Andrew Witkin and William Welch. Fast animation and control for non-rigid structures. Computer Graphics, 24(4):243--252, August

....in realism. Other approaches have animated deformable objects of fixed topology. Elasticity and visco elasticity have been modeled [TPBF87, TW88, TPF89] but these methods suffer from the same time step handicap. Global methods, gaining efficiency by restraining the possible deformation [PW89, WW90] are perfect for interactive manipulation, but offer limited realism. To the authors knowledge, only two existing models achieve real time computation for deformable structured objects. The first [CDA96] is derived from the finite element theory, and takes advantage of linear elasticity to ....

Andrew Witkin and William Welch. Fast animation and control for non-rigid structures. Computer Graphics, 24(4):243--252, August

....appropriately on the skeleton, whose dynamic motion deforms the lattices, thereby modeling soft tissue deformations. Pentland and Williams [9] employ the principal deformation modes of an elastic isoparametric hexahedral finite element to animate deforming embedded objects. Witkin and Welch [10] use polynomial global deformations in a physics based model. Baraff and Witkin [11] use global implicit deformations in conjunction with physics based simulation to animate polygonal and parametric objects. This formulation is similar to the one presented in [10] which uses deformations that are ....

....embedded objects. Witkin and Welch [10] use polynomial global deformations in a physics based model. Baraff and Witkin [11] use global implicit deformations in conjunction with physics based simulation to animate polygonal and parametric objects. This formulation is similar to the one presented in [10], which uses deformations that are linear with respect to the state of the object, and is restricted to passive objects. Terzopoulos and Qin [12] model deformable surfaces using NURBS which are given dynamic properties. They also describe a physics based deformation technique using dynamic NURBS ....

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A. Witkin and W. Welch, "Fast Animation and Control of Nonrigid Structures," Proc. ACM SIGGRAPH: Computer Graphics, vol. 24, no. 4, pp. 243--252, Aug. 1990.

....Motion is computed by independentely solving the equations of motion for each particle. Nodal approaches are often compute intensive, since very small integration steps may be required. Another class of methods, called global approaches , has been introduced to reduce computational costs [33] [45], 2] The idea is to perform global shape transformations rather than simulating deformations that progressively propagate over a deformable body. However, this leads to a restricted range of deformations, and can only be applied to the animation of homogeneous visco elastic material. The way a ....

....generate any contact surface between interacting flexible bodies, but use instead the amount of interpenetration for computing a force that pushes the objects apart. A quite promising approach [2] extends the analytical interaction processing used for rigid solids [1] to a global deformable model [45]. However, contact surfaces are approximated by discrete sets of contact points which, as the authors emphasize, is somewhat unsatisfactory. To conclude the review of related work, most previous deformable models do not present a convincing way of processing collision and contacts between ....

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Andrew Witkin and William Welch. Fast animation and control for non-rigid structures. Computer Graphics, 24(4):243--252, August

....to other immersive simulations (bottom: toy example) The approach makes use of a local refinement technique to ensure high physical fidelity while bounding the global computation load to guarantee real time animations. given set of vibration modes, or of a specific class of global deformations [23, 26]. They are less useful, however, when realistic deformations are called for. Particle and mass spring systems are based on a local description of the material. These systems allow for large deformations and displacements, and are fairly easy to implement. The equations of motion are integrated ....

A. Witkin and W. Welch. Fast animation and control for non-rigid structures. Proceedings of SIGGRAPH, 24(4):243--252, August 1990.

....also be useful in robotic motion planning. Such a system could plan movements by considering large numbers of possible motions looking for some desired outcome (similar to the way Deep Blue plays chess [1] 2 Background A wide range of techniques exist for physical modeling of solid objects [2, 3, 4, 5, 6]. Rigid body techniques [2, 5] tend to be computationally ecient on general purpose CPUs. Since the object is not allowed to deform, collision detection is the only signi cant computational challenge. The disadvantages of this approach include collision detection performance and inability to model ....

A. Witkin, W. Welch, \Fast Animation and Control of Nonrigid Structures", Computer Graphics, Vol. 24, No. 4, August 1990.

....objects off line, while constraint force methods are well suited to creating constrained models on the fly. In [5] we describe an architecture that combines both methods, allowing constraints to be applied dynamically to complex objects that had been pre defined using Lagrangian dynamics. In [6], Lagrangian dynamics is used to create simplified non rigid bodies. SIGGRAPH 98 COURSE NOTES F11 PHYSICALLY BASED MODELING ....

Andrew Witkin and William Welch. Fast animation and control of non-rigid structures. Computer Graphics, 24(4):243--252, July 1990. Proc. Siggraph '90. SIGGRAPH '98 COURSE NOTES F12 PHYSICALLY BASED MODELING

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A. Witkin and W. Welch. Fast Animation and Control of Nonrigid Structures. Computer Graphics: SIGGRAPH'90 Conference Proceedings, Aug., 1990, pp. 243-252. Pointers in Constraint Models - i -

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A. Witkin, W. Welch, \Fast Animation and Control of Nonrigid Structures", Computer Graphics, Vol. 24, No. 4, August 1990.

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Witkin A., Welch W.: Fast animation and control for non-rigid structures. In ACM SIGGRAPH Conference Proceedings, 243-252 (1990).

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Witkin, A., and Welch, W. Fast animation and control of nonrigid structures. Proceedings of SIGGRAPH'90 (Dallas, August 6--10, 1990.

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WITKIN A., WELCH W.: Fast animation and control of nonrigid structures. Proceedings of SIGGRAPH '90 (1990), 243--252. 3

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A. Witkin and W.Welch. Fast animation and control of nonrigid structures. ACM Computer Graphics (SIGGRAPH '90 Proceedings), 24(4):243--252, August 1990.

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A. Witkin and W.Welch. Fast animation and control of nonrigid structures. ACM Computer Graphics (SIGGRAPH '90 Proceedings), 24(4):243--252, August 1990.

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