PLATT J. C., BARR A. H.: Constraint methods for flexible models. Computer Graphics (Proceedings of SIGGRAPH 88) 22, 4 (August 1988), 279--288.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....and surfaces where one direction of the frame is already fixed, and the chosen functional minimization in quaternion space must obey the additional constraint imposed by the fixed family of directions. Additional references of interest, especially regarding the treatment of surfaces, include [22, 32]. Figure 3 provides a visualization of the difference between the general interpolation problem and our constrained problem: a typical spline minimizes the bending energy specified by the chosen anchor points; requiring intermediate points to slide on constrained paths during the minimization ....

PLATT, J. C., AND BARR, A. H. Constraint methods for flexible models. In Computer Graphics (SIGGRAPH '88 Proceedings) (Aug. 1988), J. Dill, Ed., vol. 22, pp. 279--288.

....stability, thus improving the interface between the animator and the physics based model. 2. The dynamic model Our work is based on the fundamental equation of motion as described by Terzopoulos et al. 15] with the damping term replaced by a more accurate one proposed by Platt et al. [14]: r (a ) 2 dr E da 1 da 2 dv E da 1 da 2 dr B B 0 da 1 da 2 = S F ex (1) Because this equation is quite similar to Eq.1 of [15] we discuss only the modified third term and refer the reader to [15] for notation and explanations. In the second ....

....this equation is quite similar to Eq.1 of [15] we discuss only the modified third term and refer the reader to [15] for notation and explanations. In the second term of Eq.1, E = G G o is called the Lagrangian strain tensor. In the third one, E is the time rate of E and is defined as [14]: E ij (r (a ) E ij = 1 G ij = 2) This term works like a dissipative function. We choose to replace it because the one used in [15] is scalar. So, no matter where energy comes from, it will be dissipated. For example, gravitational energy is dissipated, resulting in a ....

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Platt Jone C, Barr Alan H. Constraints Methods for Flexible Models. In Proc. SIGGRAPH'88 , Computer Graphics, Vol.23, No.3, 1988, pp.21-30.

.... [22] Terzopoulos and Fleischer have extended the model mixing flexible and rigid components [33] and to simulate also inelastic behavior [32] Many other techniques have been proposed to improve physically based deformations, as the methods based on constraints presented by Platt and Barr [23] and Metaxas and Terzopoulos [17] Approaches based on discretising the object into a number of particles, whose connectivity is maintained through attached springs are named massspring systems. Miller used it to animate snakes and worms [18] and currently, a lot of variations of this kind of ....

Platt, J. C. and Barr, A. H. "Constraints Methods for Flexible Models", Computer Graphics, v. 22, n. 4, p. 279288, 1988.

....physical effects. In contrast to most previous approaches that solve a sequence of static equilibrium problems only, inertially induced oscillations can take place here thus enhancing the visual realism. Muscle muscle and muscle bone collision forces are also added as reaction constraints [Platt88]. Yet, trying to simulate every muscle muscle and muscle bone interaction seems unrealistic. For example, no solution is given as to how multiple collisions between muscles are to be handled. 1.2 Overview The remainder of this paper is organised as follows. Section 2 exposes some important ....

J.Platt, A. Barr, "Constraint Methods for Flexible Models", Computer Graphics (SIGGRAPH '88 Proceedings), pp. 279-288.

.... On the other hand, the environment of characters is made up of rigid objects, key frame deformable objects, mathematically deformable objects [5] soft objects represented by scalar combinations of fields around key points [35] 7] or physically deformable objects based on elasticity theory [27] [30] With physical models, the objects act as if they had a mind. They react to applied forces such as gravity, pressure and contact. Platt and Barr [27] used finite element software and discuss constraint methods in terms of animator tools for physical model control. The models developed by ....

....objects represented by scalar combinations of fields around key points [35] 7] or physically deformable objects based on elasticity theory [27] 30] With physical models, the objects act as if they had a mind. They react to applied forces such as gravity, pressure and contact. Platt and Barr [27] used finite element software and discuss constraint methods in terms of animator tools for physical model control. The models developed by Terzopoulos et al. 30] are implemented using the Finite Difference Method. Collisions between elastic objects are simulated by creating potential energy ....

Platt JC and Barr AH. Constraint method for flexible models. Proc. SIGGRAPH '88, pp 279-288

....search starts across the neighbors to find all the colliding pairs in the area. 4.2 Collision Response We initiate the response whenever the distance between the two segments is less than the sum of their radii. The earlier approaches such as penalty method [2, 27] and reaction constraint method [21, 26] implemented collision response by altering the force matrix in the mass spring method. In our simulations, we observed that the stability of the system was reduced when we applied penalty and constraint methods. Our new method alters the displacements and velocities of the two colliding segments ....

J. C. Platt and A. H. Barr. Constraints methods for flexible models. In Proc. SIGGRAPH '88, pages 279--88. ACM Press, 1988.

....that underly the model they create realistic animations. In Turner and Gobbetti s paper [24] they state that physics based deformations derived from elastic and viscous properties of continuous media can produce realistic looking simulations but can be difficult to control. Platt and Barr [13] proposed methods using mathematical constraints based on physics and optimization theory to create and control physically based flexible models. Chadwick et al. 3] propose a layered construction approach to create deformable animated creatures, where the creatures are built in layers with the ....

Platt J. C., Barr A. H., Constraint Methods for Flexible Models, ACM SIGGRAPH 1988.

....to simulate elastic objects with regular parameterizations. This framework was extended to include inelastic behaviors [31] and to handle stiff rotating bodies using linearized equations [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 ....

John C. Platt and Alan H. Barr. Constraint methods for flexible models. Computer Graphics (Proceedings of SIGGRAPH 88), 22(4):279--288, August 1988. Held in Atlanta, Georgia.

....difference scheme to simulate elastic objects with regular parameterizations. Their framework was extended to include inelastic behaviors [41] and to handle stiff rotating bodies using linearized equations [44] Physically based deformations have since been extended in many ways. Platt and Barr [33] introduced better constraint handling via Lagrange multipliers. Pentland and Williams [31] obtained realtime simulations by using only a few vibration modes. Witkin and Welch [46] introduced the use of low order polynomial deformations to achieve fast deformations, to which Baraff and Witkin [3] ....

John C. Platt and Alan H. Barr. Constraint methods for flexible models. Computer Graphics (Proceedings of SIGGRAPH 88), 22(4):279--288, August 1988.

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PLATT J. C., BARR A. H.: Constraint methods for flexible models. Computer Graphics (Proceedings of SIGGRAPH 88) 22, 4 (August 1988), 279--288.

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Platt, J. C. and Barr, A. H. (1988). Constraint methods for flexible models. In Dill, J., editor, Computer Graphics (SIGGRAPH '88 Proceedings), volume 22, pages 279--288.

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PLATT,J.C.AND BARR, A. H. 1988. Constraint method for flexible models. In Computer Graphics (Proceedings of SIGGRAPH 88). Annual Conference Series. ACM SIGGRAPH, 279--288.

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J. C. Platt and A. H. Barr. Constraint method for flexible models. In Proceedings of SIGGRAPH'88, pages 279--288. Computer Graphics, 1988.

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J. C. Platt and A. H. Barr, 1988, "Constraint method for flexible models", Proceedings of SIGGRAPH'88, pp.

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J.C. Platt and A.H. Barr. Constraint methods for flexible models. Computer Graphics (Proceedings of ACM SIGGRAPH 88), 22(4):279--288, August 1988.

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J. Platt, and A. H. Barr, "Constraints Methods for Flexible Models", Computer Graphics, Vol.22, No.4, 1988, pp.279288.

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J. Platt and A. Barr, "Constraints Methods for Flexible Models," in Proc. SIGGRAPH '88. ACM Press, 1988, pp. 279--88.

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J.C. Platt and A. H. Barr. "Constraint Methods for Flexible Models", In Computer Graphics (Proc. SIGGRAPH), Vol. 22, No. 4, ACM SIGGRAPH, August 1988, pp. 279-288.

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J.C. Platt and A.H. Barr, Constraint Methods For Flexible Models, Computer Graphics, 22(4):279--278, 1988.

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Platt, J. C., and Barr, A. H. Constraint methods for flexible models. Proceedings of SIGGRAPH'88 (Atlanta, August 1--5, 1988.

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PLATT J. C., BARR A. H.: Constraint methods for flexible models. In Proceedings of SIGGRAPH 88 (1988), pp. 279--288. 2

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Platt, J. C. and Barr, A. H. (1988). Constraint methods for flexible models. In Dill, J., editor, Computer Graphics (SIGGRAPH '88 Proceedings), volume 22, pages 279--288.

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J. C. Platt and A. H. Barr. Constraint Methods for Flexible Models. In Computer Graphics (SIGGRAPH '88), volume 22 No 4, pages 279--288, 1988.

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Platt JC, Barr AH(1988) Constraints Methods for Flexible Models, Proc. SIGGRAPH'88, Computer Graphics, Vol.23, No.3, pp.21-30

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J.C. Platt and A.H. Barr. Constraint Methods for Flexible Models, Computer Graphics, 22(4):279--278, 1988. 2

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