Inverse kinodynamics: Editing and constraining kinematic approximations of dynamic motion

Abstract

We present inverse kinodynamics (IKD), an animator friendly kinematic work flow that both encapsulates short-lived dynamics and allows precise space-time constraints. Kinodynamics (KD), defines the system state at any given time as the result of a kinematic state in the recent past, physically simulated over a short time window to the present. KD is a well suited kinematic approximation to animated characters and other dynamic systems with dominant kinematic motion and short-lived dynamics. Given a dynamic system, we first choose an appropriate kinodynamic window size based on accelerations in the kinematic trajectory and the physical properties of the system. We then present an inverse kinodynamics (IKD) algorithm, where a kinodynamic system can precisely attain a set of animator constraints at specified times. Our approach solves the IKD problem iteratively, and is able to handle full pose or end effector constraints at both position and velocity level, as well as multiple constraints in close temporal proximity. Our approach can also be used to solve position and velocity constraints on passive systems attached to kinematically driven bodies. We describe both manual and automatic procedures for selecting the kinodynamic window size necessary to approximate the dynamic trajectory to a given accuracy. We demonstrate the convergence properties of our IKD approach, and give details of a typical work flow example that an animator would use to create an animation with our system. We show IKD to be a compelling approach to the direct kinematic control of character, with secondary dynamics via examples of skeletal dynamics and facial animation.

Inverse Kinematics Techniques in Computer Graphics: A Survey

“…[SYLH10] have additionally used momentum and force constraints. Inverse kinodynamics (IKD) [KRRS12] is another kinematic workflow that encapsulates short‐lived dynamics and allows precise space‐time constraints. More recently, Rabbani and Kry [RK16] introduced a method that respects physics during certain dynamic activities by controlling both the centre of mass, and the magnitude of the character's inertia tensor.…”

“…For instance, Lee and Goswami [LG07] used the momentum and inertia to improve the balance of the animation, Shapiro and Lee [SL11] utilized certain dynamic physical properties, such as the centre of mass and angular momentum, to allow the improvement of unrealistic motions, while Sok et al [SYLH10] have additionally used momentum and force constraints. Inverse kinodynamics (IKD) [KRRS12] is another kinematic workflow that encapsulates short-lived dynamics and allows precise space-time constraints. More recently, Rabbani and Kry [RK16] introduced a method that respects physics during certain dynamic activities by controlling both the centre of mass, and the magnitude of the character's inertia tensor.…”

Hierarchical block-based incomplete human mocap data recovery using adaptive nonnegative matrix factorization

“…Mocap data is generally recorded by the highly articulated movements in terms of the connected joints, which always holds strong temporal and spatial correlations among multiple joints [37]. As shown in Fig.…”

Automatic Generation of Dynamic Skin Deformation for Animated Characters

“…A fast physically based simulation system for skeleton-driven deformable body characters is developed in [36] that gives a well-coordinated combination of a reduced deformable body model with nonlinear finite elements, a linear-time algorithm for skeleton dynamics, and explicit integration, to boost simulation speed. In [37], EigenSkin has been presented to correct SSD results, it achieves high frame rates per second, but constructing one proper error-optimal eigen displacement basis requires sufficient experience and background knowledge. Since it is not easy to model the different elastic behaviors of muscle, fat and skin using simple volumetric mesh, [38] introduce one novel multi-layer model to simulate them, but it fails handle collisions during fast motions.…”