Methods for exploring expressive stance

Abstract

The postures a character adopts over time are a key expressive aspect of its movement. While IK tools help a character achieve positioning constraints, there are few tools that help an animator with the expressive aspects of a character's poses. Three aspects are required in good pose design: achieving a set of world space constraints, finding a body shape that reflects the character's inner state and personality, and making adjustments to balance that act to strengthen the pose and also maintain realism. This is routinely done in the performing arts, but is uncommon in computer graphics. Our system combines all three components within a single body shape solver. The system combines feedback based balance control with a hybrid IK system that utilizes optimization based and analytic IK components. The IK system has been carefully designed to allow direct control over various aesthetically important aspects of body shape, such as the type of curve in the spine and the relationship between the collar bones. The system allows for both low-level control and for higher level shape sets to be defined and used. Shape sets allow an animator to use a single scalar to vary a character's pose within a specified shape class, providing an intuitive parameterization of a posture. Changing a shape set allows an animator to quickly experiment with different posture options for a movement sequence, supporting rapid exploration of the aesthetic space.

Gesture modeling and animation based on a probabilistic re-creation of speaker style

“…Posture Parameters Curvature to the spine or offset to the collarbones based on the parameterization presented in [Neff and Fiume 2006]. Balance and pelvic tilt adjustments may also be included.…”

Modelling multimodal expression of emotion in a virtual agent

“…The model adds expressivity to the final animation. Other work is based on motion capture to acquire the expressivity of behaviours during a physical action, a walk or a run (Ménardais et al 2004;Neff & Fiume 2004;Liu & Hertzmann 2005). Based on perceptual studies conducted by Wallbott & Scherer (1986) and Wallbott (1998) a model of nonverbal behaviour expressivity has been defined that acts on the synthesis computation of a behaviour (Hartmann et al 2005).…”

Interactive editing of motion style using drives and correlations

“…This approach to solving for a pose takes inspiration from the geometric view of IK adopted in [NF04], but varies in important ways, including additional lower body parameters, different prioritization of the parameters, a different approach to balance correction, and no use of optimization.…”

“…[GM85,YN03]). Style is explicitly addressed in [NF04] for standing characters using shape sets inspired by the arts literature. Kulpa et al [KMA05] present a system that also uses positional data instead of joint angles for reconstructing motion, but their intent is different, adapting motion to different character morphology rather than editing motion style.…”