GIRARD, M., AND MACIEJEWSKI, A. A. 1985. Computational Modeling for the Computer Animation of Legged Figures. In Computer Graphics (Proc. of SIGGRAPH 85), vol. 19, 263--270.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....animals by combining kinematics, dynamics, and control theory. A variety of techniques have been used to address some of the problems within the general area of articulated figure locomotion, applied both to humans ( BC89] Hod94] vFV92] Wil86] WS89] and legged animals ( Gir87] [GM85], RH91] MZ90] However, each of the above techniques addresses only a subset of the problems associated with autonomous animation. In this paper, we develop a unified framework aimed to address in a formal way the autonomous locomotion in variable terrain, smooth gait transitions, and simple ....

Michael Girard and A. A. Maciejewski. Computational modeling for the computer animation of legged figures. In SIGGRAPH, volume 19, 1985.

....task. As such, it should be able to improve the understanding of posture control for general reach tasks. Unfortunately, due to a lack of strength data for other joints, the model is limited to the upper body and especially the arm chain, from the shoulder to the hand[4] Other approaches [5][6][7] have also considered the control of the center of mass. The system presented in [6] dedicated to bipedal walking, is mostly kinematic but also includes some dynamic rules so as to maintain the center of mass within the support polygon. A similar approach [5] has defined kinematic and dynamic ....

....for general reach tasks. Unfortunately, due to a lack of strength data for other joints, the model is limited to the upper body and especially the arm chain, from the shoulder to the hand[4] Other approaches [5] 6] 7] have also considered the control of the center of mass. The system presented in [6], dedicated to bipedal walking, is mostly kinematic but also includes some dynamic rules so as to maintain the center of mass within the support polygon. A similar approach [5] has defined kinematic and dynamic rules so as to partially control the balance via the position of the center of mass, ....

Girard M., Maciejewski A.A. " Computational Modeling for the Computer Animation of Legged Figures". Computer Graphics 19 (3),1985, pp263-270

....the burden of an animator by shifting the tedious task of detailed motion specification to an automated controller. The abstraction of motion mechanism from different points of views engendered several paradigms of motion control: dynamic models [27,1,12,7,17,19,21,11] inverse kinematics models [10,15,20,5]. In dynamic models, forces and torques generating a particular motion are computed where as in inverse kinematics, an end goal is specified and an articulated structure is expected to reach it through an end effector subject to certain kinematic constraints. While inverse kinematics models are ....

Girard Michael, Maciejewski, A.A., Computational Modeling for the Computer Animation of Legged Figures, Computer Graphics, 19, 3 (July, 1985), 263-270

....redundant degrees of freedom exist) and it becomes singular 17 in some configurations of a chain. To accommodate for the redundant case, a more generalised replacement for is typically used Some research has adopted the pseudoinverse J for this purpose [Klein and Huang, 1983, Girard and Maciejewski, 1985]. Use of the pseudoinverse allows solutions to be produced for rectangular Jacobian matrices, although there are still issues with singularities in the matrix Such singularities may be caused when identical derivatives exist for several joint parameters of the system, such as when all ....

Girard, M. and Maciejewski, A. A. (1985). Computational modeling for the computer animation of legged figures. In Barsky, B. A., editor, Computer Graphics (SIGGRAPH 85 Proceedings), volume 19, pages 263---270.

....with the measurements obtained from NASA experiments for three reach tasks without loads. It is difficult to assess the validity of this approach only from geometric data ; one would have expected the values of the joint torques over time, at least from the simulation. Other approaches [5] [6], 7] have also considered the control of the center of mass. The system presented in [6] dedicated to bipedal walking, is mostly kinematic but also includes some dynamic rules so as to maintain the center of mass within the support polygon. A similar approach [5] has defined kinematic and ....

....loads. It is difficult to assess the validity of this approach only from geometric data ; one would have expected the values of the joint torques over time, at least from the simulation. Other approaches [5] 6] 7] have also considered the control of the center of mass. The system presented in [6], dedicated to bipedal walking, is mostly kinematic but also includes some dynamic rules so as to maintain the center of mass within the support polygon. A similar approach [5] has defined kinematic and dynamic rules so as to partially control the balance via the position of the center of mass, ....

Girard M., Maciejewski A.A. " Computational Modeling for the Computer Animation of Legged Figures". Computer Graphics 19 (3),1985, pp263-270

....Dimension Toolkit. keywords: Articulated Figure Animation, Motion Editing, Direct Kinematics, Inverse Kinematics, Keyframing . 1. Introduction Human animation is an active research field, including various approaches from traditional rotoscopy [1] key framing [2,3,4,5] functional modelling [6,7,8,9], direct and inverse kinematics [10,11,12] to physically based methods like direct and inverse dynamics [13,14,15] and spacetime optimization [16,17] Integration of different motion generators is vital for the design of complex motion where the characterization of movement can quickly change ....

. Girard M, Maciejewski AA (1985) Computational Modeling for the Computer animation of Legged Figures, Proc. SIGGRAPH '85, Computer Graphics, Vol.

....actors. 2 Background The use of behavioral animation to generate computer animation is a well explored domain. Reynolds [18] described the first use of a behavioral model to produce a flocking behavior. Other papers focused mainly on specific motion such as locomotion, grasping, and lifting [3, 6, 8, 13, 17]. Tu and Terzopoulos [19] created autonomous fishes living in a physically modeled virtual marine world. Hodgins et al. 10] described dynamic athletic behaviors. Unuma et al. 20] modeled human figure locomotion with emotions. Other papers presented systems to interact with virtual creatures. ....

Girard, Michael and A. A. Maciejewski. Computational Modeling for the Computer Animation of Legged

....realization of three control levels of decreasing priority: balance control, end effector control, and gravity torques minimization. 2B ACKGROUND The direct position control of the center of mass has received increasing attention with the development of 3D human and animal character design [10], 11] 12] and human factors evaluation in complex environments [1] In [23] the center of mass of a human figure is considered as an end effector attached to the lower torso region. Its position is controlled with an iterative process based on Inverse Kinematics. The constraint variables ....

....is called Inverse Kinetics because it combines the information of the articulated structure kinematics together with its mass distribution. Inverse Kinetics can be combined with Inverse Kinematics in a hierarchical fashion with the homogeneous component of Inverse Kinematics general solution [4] [10], 18] 20] A first attempt to generalize Inverse Kinetics to the multiple supports case is described in [5] The concept of Influence Tree was introduced to represent the fraction of the body supported by a given supporting site. However, the associated algorithm lacked a coherent treatment ....

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M. Girard and A.A. Maciejewski, "Computational Modeling for the Computer Animation of Legged Figures," Computer Graphics, vol. 19, no. 3, pp. 263-270, 1985.

....all the degrees of freedom, leading to smooth and parameterizable walking gaits. Note that the same kind of approach has more recently been used for the animation of human running [10] Another way to maintain extra constraints on the foot position is to use inverse kinematic algorithms [22, 21, 4, 6]. Boulic et al. 4] first use a standard forward kinematics approach, generating key positions that are interpolated. A leg correction process is then used to modify invalid in between postures: 5 if a foot penetrates the ground, an inverse kinematic algorithm is applied to modify its position, ....

M. Girard and A.A. Maciejewski. Computational modeling for the computer animation of legged

....procedurally approaches, kinematics, or based on dynamics computation. Some of the earlier human motion models in computer animation exploited this concept implicitly by using procedurally generated motion, simplified dynamics and control algorithms, off line motion mapping, or motion play back [1, 2, 5, 11, 12, 17, 21]. Carlson and Hodgins explored techniques for reducing the computational cost of simulating groups of legged creatures when they are less important to the viewer or to the action in the virtual world [3] In this work, the generation of simulation LODs, switching and selection are designed by ....

M. Girard and A. Maciejewski. Computational modeling for computer animation of legged figures. In Computer Graphics (Proc. of SIGGRAPH), volume 19, pages 263--270, 1985.

....to algorithmic assistance are kinematically controlled, and dynamically controlled positioning. Wilhelms has described a system Virya [22, 23] which controls animation using dynamics. Armstrong and Green [2] have also discussed the dynamics of rigid bodies for animation. Girard and Maciejewski [10] have designed a system that facilitates animation of a walking mulfidegged animal. This system is novel since the user defines the path and type of the walk and it uses a combination of dynamics and kinematics to achieve the key positions. A different approach taln by Zeltzer [24] ha been to ....

....especially with the presence of redundant degrees of freedom (as in a human figure) One solution is the inverse or pseudo inverse jacobian matrix, used in the field of robotics [17] Figure A model of the human body used by TEMPUS. and lately used in the control of animation of legged figures [ 10]. Another solutio is described by Korein [13] who defines the work space of each joint as a spherical polygon: the intersection of the polyb edra created by sweeping the segments through the spherical polygon joint limits leads to a recursire formulation of the solution. Another approach to solve ....

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Girard, Michael and A. A. Maciejewsld. "Computational modeling for the computer animation of legged figures". Computer Graphics 19, 3 (1985), 263-270.

.... Since this algorithm concentrates of locomotion it only considers locomotion specific artefacts such as foot slipping and ground penetration (Figure 4) Prima facie, correction of these constraints does not represent a problem the motion analysis provides all information needed for IK solver [8, 9] to ensure satisfaction of the constraints. The problem however is how to correct the motion without introducing new artefacts and without losing important details of the original motion. We identified several requirements that a retargetting algorithm should satisfy in order to achieve a good ....

Girard, M., Maciejewski, A. (1985). "Computational modeling for the computer animation of legged figures", Proceedings of SIGGRAPH '85, 263-270

....properly maneuver his or her avatar. He looks like a guy who s just goggled into the Metaverse for the first time and doesn t know how to move around (page 203) Real time avatar locomotion has been rather extensively studied. There are several examples for gait, walking, and arbitrary stepping [42, 8, 20, 29, 51, 34]. 2.5. Body Action Stephenson describes a wide variety of body actions (see Appendix E) These range from things as simplistic as gesturing to the wall or sitting motionless or waving toward the next quadrant to more intricate actions such as pulling a hypercard out of her pocket or ....

M. Girard and A. Maciejewski. Computational modeling for the computer animation of legged figures. In SIGGRAPH '85 Proceedings, pages 263--270, 1985.

....and are surveyed in [14] The simplest approach is to solve the constraints at each instant in time individually. Such an approach has the advantage that it solves a series of small kinematic problems. A wide range of techniques including direct solution [26] and iterative numerical methods [11] have been applied to these inverse kinematics problems, and solutions are widely available. The problem is that solving each problem frame as an independent problem is that there is no way to maintain consistency across the subproblems. Many of the consistency issues come from constraint ....

Michael Girard and Anthony A. Maciejewski. Computational modeling for the computer animation of legged figures. In B. A. Barsky, editor, Computer Graphics (SIGGRAPH '85 Proceedings), volume 19, pages 263--270, July 1985.

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GIRARD, M., AND MACIEJEWSKI, A. A. 1985. Computational Modeling for the Computer Animation of Legged Figures. In Computer Graphics (Proc. of SIGGRAPH 85), vol. 19, 263--270.

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M. Girard, A. A. Maciejewski, Computational modeling for the computer animation of legged figures, Computer Graphics (Proceedings of SIGGRAPH 85) 19 (3) (July 1985) 263--270.

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GIRARD M., MACIEJEWSKI A. A.: Computational modeling for the computer animation of legged figures. Computer Graphics (Proceedings of SIGGRAPH 85) 19, 3 (July 1985), 263--270. Held in San Francisco, California. 3

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M. Girard and A. Maciejewski, "Computational modeling for the computer animation of legged figures," ACM Computer Graphics, 19(3):263270, 1985.

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Girard M, Maciejewski A. Computational Modeling for the Computer Animation of Legged Figures. Computer Graphics. 19(3), July 1985, Pages 253-270.

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Girard, M., and Maciejweski, A. Computational modeling for the computer animation of legged figures. In Computer Graphics (SIGGRAPH '85 Proceedings) (1985), vol. 19, pp. 263--270.

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M. Girard and A.A. Maciejewski. Computational modeling for the computer animation of legged figures. In Proceedings of SIGGRAPH 85, volume 20, pages 263--270, 1985.

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M. Girard and A. Maciejewski. Computational modeling for computer animation of legged figures. In Computer Graphics (Proc. of SIGGRAPH), volume 19, pages 263--270, 1985.

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M. Girard and A. Maciejewski. Computational Modeling for the Computer Animation of Legged Figures. In Computer Graphics (SIGGRAPH 85 Conference Proceedings), pages 263--270, 1985.

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Girard, Michael, and Maciejewski, Anthony. Computational Modeling for the Computer Animation of Legged Figures. Proceedings of SIGGRAPH'85 (San Francisco, California, July 22-26,

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Girard, M. and Maciejewski, A.A., "Computational Modeling of the Computer Animation of Legged

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