We describe a semi-automatic technique for modeling and animating complex musculoskeletal systems using a strand based muscle model. Using our interactive tools, we are able to generate the motion of tendons and muscles under the skin of a traditionally animated character. This is achieved by integrating the traditional animation pipeline with a biomechanical simulator capable of dynamic simulation with complex routing constraints on muscles and tendons. We integrate our musculoskeletal modeling and animation toolkit into a professional 3D production environment, thereby enabling artists and scientists to create complex musculoskeletal systems that were previously inaccessible to them. We demonstrate the applications of our tools to the visual effects industry with several animations of the human hand and applications to the biomechanics community with a novel model of the human shoulder.

We describe a semi-automatic technique for modeling and animating complex musculoskeletal systems using a strand based muscle model. Using our interactive tools, we are able to generate the motion of tendons and muscles under the skin of a traditionally animated character. This is achieved by integrating the traditional animation pipeline with a biomechanical simulator capable of dynamic simulation with complex routing constraints on muscles and tendons. We integrate our musculoskeletal modeling and animation toolkit into a professional 3D production environment, thereby enabling artists and scientists to create complex musculoskeletal systems that were previously inaccessible to them. We demonstrate the applications of our tools to the visual effects industry with several animations of the human hand and applications to the biomechanics community with a novel model of the human shoulder.

We describe a semi-automatic technique for modeling and animating complex musculoskeletal systems using a strand based muscle model. Using our interactive tools, we are able to generate the motion of tendons and muscles under the skin of a traditionally animated character. This is achieved by integrating the traditional animation pipeline with a biomechanical simulator capable of dynamic simulation with complex routing constraints on muscles and tendons. We integrate our musculoskeletal modeling and animation toolkit into a professional 3D production environment, thereby enabling artists and scientists to create complex musculoskeletal systems that were previously inaccessible to them. We demonstrate the applications of our tools to the visual effects industry with several animations of the human hand and applications to the biomechanics community with a novel model of the human shoulder. / Science, Faculty of / Computer Science, Department of / Graduate

Wall-dominated turbulent dispersed multiphase flows occur in a variety of industrial, biological and environmental applications. The complex nature of the  arrier and the dispersed phase is elevated to a higher level introducing geometrical complexities such as curved walls. Realising such flows and particulate phases poses challenging problems both from computational and also physical point of view. The present thesis tries to address some of these issues Lagrangian computational frame. In the first step, turbulent flow in straight pipes is simulated by means ofdirect numerical simulation with a spectrally accurate code nek5000 to examine the Reynolds number effect on turbulent statistics. Adding the effect of the curvature to these canonical turbulent pipe flows generates Prandtl’s secondary motion of first kind. These configurations, as primary complex geometries in this study, are examined by means of statistical analysis to unfold the evolutionof turbulent characteristics from a straight pipe configuration. A fundamentally different Prandtl’s secondary motion of second kind is also put to test by means of adding the side-walls to a canonical turbulent channel flow and the evolution of various statistical quantities with varying the duct aspect ratios is discussed. After having obtained a characterisation of the turbulent flow in the geometries of bent pipes and ducts, the dispersion of small heavy particles is modelled in the bent pipe by means of point particles which are one-way coupled to the flow. For this purpose a parallel Lagrangian Particle Tracking (LPT) scheme is implemented in the spectral-element code nek5000. Its numerical accuracy, parallel scalability and general performance in realistic situations are scrutinised in various situations. Also, the resulting particle fields are analysed, showing that even a small degree of geometrical curvature has a profound impact on the particle concentration maps. For each of the aforementioned turbulent flow cases new and challenging questions have arisen to be addressed in the present and upcoming research works. Along with an improved understanding of the particle dispersion in the considered complex geometries, the current project is particularly intended to improve the numerical aspects of the current LPT module suitable for largescale computations. / <p>QC 20140226</p>

Background. Secondary motion is a principle of animation, it is movement that occurs as a result of other movement, such as swinging hair or clothes. In 3D animation, such as in games, it is often simulated instead of animated manually. In game projects with time limitations, it can be interesting to know to what degree these simulations impact the visual quality in order to decide whether they should be prioritized. It is also interesting to know how the results of various methods compare to each other. To simulate in real-time means that physics simulations are running during gameplay. Baked animations on the other hand are simulations that have already been processed and saved as animation data, they are less dynamic but also less performance intensive. Objectives. The aim of this thesis is to evaluate the impact of three sets of animations by conducting a survey where each set is compared. The three sets are: animations that feature real-time simulations, baked simulations and ones without simulation. The goal is to acquire a metric from the comparisons that can give an insight to the visual quality impact of each method. Methods. Three animation sets were created. Then, a survey was conducted using a questionnaire that featured side by side video comparisons of the animation sets. The videos featured a stylized character running, walking, or jumping through an empty environment. Pairwise similarity judgements were done by asking the participants to rate each video compared to each other. The results from the questionnaire were analyzed using a method that is a part of the analytical hierarchy process. The data from each comparison was averaged, put into pairwise comparison matrices, and then used to calculate priority vectors. The level of consistency of the comparisons were also calculated. Results. The priority vectors show the ratios of how each animation set were preferred compared to each other. In the priority vector for all animations combined, the set without simulations ranked at twenty-four percent, the real-time set ranked at thirty-three percent and the baked set ranked the highest at forty-three percent. The comparisons were calculated to have a very high consistency, which strengthens the result. Conclusions. The results show the impact that adding simulated secondary motion has. The simulations appear to improve the visual quality, but the margin is not extreme. The calculated ratios could be used to argue for or against a game project’s prioritization of secondary motion simulations depending on the project’s time constraints and access to preexisting methods of simulation. It should be noted that the format of video comparisons did not showcase all the advantages of each method such as creation accessibility, technical performance or dynamicity. As such, it is uncertain how fair the comparisons of the baked and real-time simulations are in a more general sense. Nevertheless, the results are considered to give at least a partial insight into how these methods compare.

Among the different types of flows encountered in practical applications, the physics of turbulent separated flows and turbulence induced secondary motion are not fully understood despite the large amount of previous experimental and numerical work. The objectives of this work are to study theoretically and computationally the conditions at the separation and reattachment point, the numerical simulation of turbulence induced secondary motion in non-circular ducts, and to provide a comprehensive test of different RANS models of these types of flow. In a theoretical study of flow separation, a Lagrangian approach was first used to derive an Eulerian criterion, which associates separation and reattachment points to a critical point in the eigenvalues of the Cauchy-Green tensor. A turbulent separated boundary layer under the influence of an adverse pressure gradient was simulated using DNS and LES techniques. A bootstrapping method was used to obtain high fidelity results at a relatively high Reynolds number with which the performance of some of the most commonly used eddy-viscosity turbulence models was evaluated. The DNS and LES results were used to assess the consistency of the different terms in the k−e , ζ −f , k −ω and Spalart-Allmaras models. Different wall-modelling techniques were employed for the calculation of separated boundary layers. The exact values of the modelled terms were calculated using the reference DNS and LES dataset. These results were used for both a priori and a posteriori tests. It was determined that the eddy-viscosity assumption works well, and that anisotropic effects are not significant in separated boundary layer. For the secondary flow calculation in non-circular ducts, direct numerical simulations of turbulent flow in square and skewed ducts were carried out to determine the effect of the duct (rhombus) included angle on both the mean and turbulence energy budgets. Two skewed ducts, with included angles of 30 and 60 degrees, were simulated. The capability of different turbulence models to predict the secondary velocity field was investigated. Results obtained from a non-linear stress-strain constitutive relation was found to be fairly accurate for the flows at the range of Reynolds number considered in this study. / Thesis (Ph.D, Mechanical and Materials Engineering) -- Queen's University, 2010-11-26 13:52:18.361