Virtual skeleton methodology for athlete posture modification in CFD simulations

This study focuses on the aerodynamic influence of athlete posture in sports aerodynamics. To analyze a specific posture, wind tunnel measurements and computer simulations are commonly employed. For computer simulations, the growing trend is to use 3D scanning to create accurate representations of an athlete’s geometry. However, this process becomes cumbersome and time-consuming when multiple positions need to be scanned. This work presents a methodology to use a virtual skeleton to perform modifications of an athlete’s posture. This is an efficient approach that can be applied directly to a scanned geometry model, and that allows easy modification and use in optimization procedures. The methodology is applied to two different cases; small adjustment of arm position for a time-trial cyclist, and large alteration of a standing alpine skier into a tucked position. Computational fluid dynamics simulations show that similar results are obtained for aerodynamic drag using the proposed methodology as with geometry models obtained from 3D scanning. Less than 1% difference in drag area was found for the cyclist, and less than 2% difference for the skier. These findings show the method’s potential for efficient use in sports aerodynamics studies.publishedVersio

The computer synthesis of expressive three-dimensional facial character animation.

This present research is concerned with the design, development and implementation of three-dimensional computer-generated facial images capable of expression gesture and speech. A review of previous work in chapter one shows that to date the model of computer-generated faces has been one in which construction and animation were not separated and which therefore possessed only a limited expressive range. It is argued in chapter two that the physical description of the face cannot be seen as originating from a single generic mould. Chapter three therefore describes data acquisition techniques employed in the computer generation of free-form surfaces which are applicable to three-dimensional faces. Expressions are the result of the distortion of the surface of the skin by the complex interactions of bone, muscle and skin. Chapter four demonstrates with static images and short animation sequences in video that a muscle model process algorithm can simulate the primary characteristics of the facial muscles. Three-dimensional speech synchronization was the most complex problem to achieve effectively. Chapter five describes two successful approaches: the direct mapping of mouth shapes in two dimensions to the model in three dimensions, and geometric distortions of the mouth created by the contraction of specified muscle combinations. Chapter six describes the implementation of software for this research and argues the case for a parametric approach. Chapter seven is concerned with the control of facial articulations and discusses a more biological approach to these. Finally chapter eight draws conclusions from the present research and suggests further extensions

Realistic rendering of a multi-layered human body model

Cataloged from PDF version of article.In this thesis study, a framework is proposed and implemented for the realistic rendering of a multi-layered human body model while it is moving. The proposed human body model is composed of three layers: a skeleton layer, a muscle layer, and a skin layer. The skeleton layer, represented by a set of joints and bones, controls the animation of the human body model using inverse kinematics. Muscles are represented by action lines, which are defined by a set of control points. The action line expresses the force produced by a muscle on the bones and on the skin mesh. The skin layer is modeled in a 3D modeler and deformed during animation by binding the skin layer to both the skeleton layer and the muscle layer. The skin is deformed by a two-step algorithm according to the current state of the skeleton and muscle layers. In the first step, the skin is deformed by a variant of the skinning algorithm, which deforms the skin based on the motion of the skeleton. In the second step, the skin is deformed by the underlying muscular layer. Visual results produced by the implementation is also presented. Performance experiments show that it is possible to obtain real-time frame rates for a moderately complex human model containing approximately 33,000 triangles on the skin layerYeşil, Mehmet ŞahinM.S

Crowd modeling: generation of a fully articulated crowd of characters

In this thesis I present a fast, efficient, and production friendly method to generate a crowd of fully articulated characters. A wide variety of characters can be created from a relatively few base models. The models that are generated are anatomically different from each another, while maintaining the same topology. They all have individual characteristics and features, that distinguish them from the others in the crowd. This method is easily adaptable to different kinds of characters, from hyper-realistic characters to highly stylized characters, and from human characters to insects like spiders. The crowd character models generated by this method are fully articulated and are ready to be animated