Animating Human Locomotion with Inverse Dynamics

Locomotion is a major component of human activity, and there have been many attempts to reveal its principles through the application of physics and dynamics. Both computer graphics and robotics continue such efforts, but many problems remain unsolved, even in characterizing the simplest case: linear, forward, rhythmic walking

Toward a computational theory for motion understanding: The expert animators model

Artificial intelligence researchers claim to understand some aspect of human intelligence when their model is able to emulate it. In the context of computer graphics, the ability to go from motion representation to convincing animation should accordingly be treated not simply as a trick for computer graphics programmers but as important epistemological and methodological goal. In this paper we investigate a unifying model for animating a group of articulated bodies such as humans and robots in a three-dimensional environment. The proposed model is considered in the framework of knowledge representation and processing, with special reference to motion knowledge. The model is meant to help setting the basis for a computational theory for motion understanding applied to articulated bodies

Real Time Animation of Virtual Humans: A Trade-off Between Naturalness and Control

Virtual humans are employed in many interactive applications using 3D virtual environments, including (serious) games. The motion of such virtual humans should look realistic (or ‘natural’) and allow interaction with the surroundings and other (virtual) humans. Current animation techniques differ in the trade-off they offer between motion naturalness and the control that can be exerted over the motion. We show mechanisms to parametrize, combine (on different body parts) and concatenate motions generated by different animation techniques. We discuss several aspects of motion naturalness and show how it can be evaluated. We conclude by showing the promise of combinations of different animation paradigms to enhance both naturalness and control

Data-driven techniques for animating virtual characters

One of the key goals of current research in data-driven computer animation is the synthesis of new motion sequences from existing motion data. This thesis presents three novel techniques for synthesising the motion of a virtual character from existing motion data and develops a framework of solutions to key character animation problems. The first motion synthesis technique presented is based on the character’s locomotion composition process. This technique examines the ability of synthesising a variety of character’s locomotion behaviours while easily specified constraints (footprints) are placed in the three-dimensional space. This is achieved by analysing existing motion data, and by assigning the locomotion behaviour transition process to transition graphs that are responsible for providing information about this process. However, virtual characters should also be able to animate according to different style variations. Therefore, a second technique to synthesise real-time style variations of character’s motion. A novel technique is developed that uses correlation between two different motion styles, and by assigning the motion synthesis process to a parameterised maximum a posteriori (MAP) framework retrieves the desire style content of the input motion in real-time, enhancing the realism of the new synthesised motion sequence. The third technique presents the ability to synthesise the motion of the character’s fingers either o↵-line or in real-time during the performance capture process. The advantage of both techniques is their ability to assign the motion searching process to motion features. The presented technique is able to estimate and synthesise a valid motion of the character’s fingers, enhancing the realism of the input motion. To conclude, this thesis demonstrates that these three novel techniques combine in to a framework that enables the realistic synthesis of virtual character movements, eliminating the post processing, as well as enabling fast synthesis of the required motion

Velocity based controllers for dynamic character animation

Dynamic character animation is a technique used to create character movements based on physics laws. Proportional derivative (PD) controllers are one of the preferred techniques in real time character simulations for driving the state of the character from its current state to a new target-state. In this paper is presented an alternative approach named velocity based controllers that are able to introduce into the dynamical system desired limbs relative velocities as constraints. As a result, the presented technique takes into account all the dynamical system to calculate the forces that transform our character from its current state to the target-state. This technique allows realtime simulation, uses a straightforward parameterization for the character muscle force capabilities and it is robust to disturbances. The paper shows the controllers capabilities for the case of human gait animation.Postprint (published version

Intermittent Non-Rhythmic Human Stepping and Locomotion

When humans need to get from one location to another, there are many occasions where non-rhythmic stepping (NRS) is more desirable than normal walking. This can be observed in performing tasks in a constricted work space. For this purpose NRS is considered as a variation of curved path walking. Four types of local adjustment are dealt with: forward, backward, lateral stepping, and turnaround. Combined with curved path walking, NRS provides a very useful tool for animating human locomotion behaviors. In the lower body motion, the trajectory of the hip, angular trajectory of the feet, and the trajectory of the swing ankle during the swing phase determine the basic outline of an NRS. These trajectories are precomputed at the start of each step. The stepping process is called with a normalized time to generate the actual pose of the NRS at that moment. the normalized time is a logical time, covering zero to one during a complete step