Practical and realistic animation of cloth

In this paper, we propose a system for the practical animation of cloth materials. A mass spring based cloth model is used. Explicit time integration methods are used to solve the equations of motion. We update the spring constants dynamically according to the net force acting on them. In this way, spring constants do not grow arbitrarily to introduce numerical instability and realistic cloth appearance without over elongation is obtained. © 2007 IEEE

대칭적인 의상의 시뮬레이션 가속을 위한 패턴 미러링 알고리즘

학위논문 (석사)-- 서울대학교 대학원 : 공과대학 전기·정보공학부, 2019. 2. 고형석.본 논문은 의상-바디 시뮬레이션의 속도 향상을 위한 패턴미러링 방법을 제시한다. 이 방법은 몸 매쉬와 옷의 패널이 위치한 Y-Z평면에 대해 대칭일 경우에 사용가능하다. 보통의 남성복이나 기성복과 같은 옷이 좌우가 대칭인 경우가 많다. 기존 시뮬레이션에서는 모든 옷의 정점들에 대해 conjugate gradient 방법을 이용해 시스템 행렬을 풀었다. 문제는 conjugate gradient 방법은 정점 수에 대해 지수적인 시간 복잡도를 가지므로, 고해상도를 위해 정점의 수가 증가할수록 시뮬레이션 시간이 지수적으로 증가한다는 것이다. Pattern Mirroring 방법을 이용하면 계산해야하는 시스템 방정식의 양이 반절로 줄어들기 때문에, 시뮬레이션에 필요한 시간도 줄어들거라고 기대할 수 있다. 결과적으로 패턴미러링 알고리즘을 이용하면 1.4배 (37%)의 속도 향상을 보였다. 1장 도입에서는 옷을 시뮬레이션하는 과정인 시스템 방정식을 푸는 방법, 충돌처리를 하는 방법에 대해 설명한다. iterative method인 conjugate gradient가 옷의 정점들의 속도를 결정하기 위해 사용되었다. 2장 관련 연구에서는 시뮬레이션 가속화를 위한 연구를 소개한다. 3장에서 pattern mirroring 알고리즘을 소개한다. 4장에서는 패턴 미러링 방법을 사용한다면 발생할 수 있는 문제가 몇가지 있는데, 이 문제를 해결하는 방법에 대해 설명한다. 5장에서는 패턴 미러링 방법을 기존의 시뮬레이션 방법과 비교해서 속도 향상을 도표로 제시하고, 결과 이미지를 비교한다.This paper describes the Pattern mirroring algorithm to reduce simulation time for cloth body simulation. This method is applicable for symmetric panel and symmetric body meshes centered on YZ plane: typically, man's suit and ready-make cloth is target of this method. As the ordinal simulation method, apply conjugate gradient method to every vertices on cloth mesh in order to solve system matrix. The problem is that the time for simulation is getting longer as the number of cloth vertices increases for high resolution. This is because the time complexity of conjugate gradient is exponential. Using pattern mirroring method, size of system matrix equation is half comparing ordinal method. So I can expect that the time for simulation reduces. The proposed method reduces simulation time up to 1.4 times (37%), by halving the matrix size of the linear equation. At chapter 1 introduction, describe the process of simulation, method of solving system equation and collision handling. An iterative method 'conjugate gradient method' is used to determine velocity of vertices of clothes. At chapter 2 relative work, explain about previous acceleration research for cloth simulation. At chapter 3, explain Pattern mirroring algorithm. But some problems could occur when using this method. At chapter 4, suggest solutions to handle these artifact as post-process step. At chapter 5, represent table to comparing the average time to simulate cloth in ordinal method and pattern mirroring method. Also represent image to difference of two result. Finally at chapter 6, describe conclusion and limitation of Pattern mirroring algorithm.Abstract Contents List of Figures List of Tables 1 Introduction 1.1 Time integration method 1.2 System matrix 1.3 Conjugate gradient method 1.4 Collision handling method 1.5 Overview of Pattern mirroring algorithm 2 Previous Work 3 Pattern Mirroring Method 3.1 1st step: Set Constraint Plane and Halving Mesh 3.2 2nd step: Simulation for Half Pane 3.3 3rd step: Mirroring Half Mesh 4 Artifacts Handling 4.1 Project crossed vertices at halving step 4.2 Penetration between original and mirrored mesh 5 Experiment Result 5.1 T-shirt 5.2 Jacket 6 Conclusion Bibliography 초록 감사의글Maste

Haptic feedback from human tissues of various stiffness and homogeneity

This work presents methods for haptic modelling of soft and hard tissue with varying stiffness. The model provides visualization of deformation and calculates force feedback during simulated epidural needle insertion. A spring-mass-damper (SMD) network is configured from magnetic resonance image (MRI) slices of patient’s lumbar region to represent varying stiffness throughout tissue structure. Reaction force is calculated from the SMD network and a haptic device is configured to produce a needle insertion simulation. The user can feel the changing forces as the needle is inserted through tissue layers and ligaments. Methods for calculating the force feedback at various depths of needle insertion are presented. Voxelization is used to fill ligament surface meshes with spring mass damper assemblies for simulated needle insertion into soft and hard tissues. Modelled vertebrae cannot be pierced by the needle. Graphs were produced during simulated needle insertions to compare the applied force to haptic reaction force. Preliminary saline pressure measurements during Tuohy epidural needle insertion are also used as a basis for forces generated in the simulation

Modeling and estimation of internal friction in cloth

Force-deformation measurements of cloth exhibit significant hysteresis, and many researchers have identified internal friction as the source of this effect. However, it has not been incorporated into computer animation models of cloth. In this paper, we propose a model of internal friction based on an augmented reparameterization of Dahl's model, and we show that this model provides a good match to several important features of cloth hysteresis even with a minimal set of parameters. We also propose novel parameter estimation procedures that are based on simple and inexpensive setups and need only sparse data, as opposed to the complex hardware and dense data acquisition of previous methods. Finally, we provide an algorithm for the efficient simulation of internal friction, and we demonstrate it on simulation examples that show disparate behavior with and without internal friction

Dynamic Cloth for the Digital Character

Cloth simulation tends to have a lingering reputation for being notoriously complex and therefore casually avoided. Very few artists are enthusiastic about a cloth simulator\u27s primary use, and perhaps even fewer would consider cloth simulation for anything other than clothing. This thesis presents typical practices of cloth simulation based on the artistic perspective of a Cloth Technical Director (TD) who worked on the animated feature film and applied case study, Cloudy with a Chance of Meatballs (2009). Through proof of concept using a generic character, simple props, and commercial software, key techniques are demonstrated to replicate the workflow of clothing the digital character as performed by artists at Sony Pictures Imageworks. The result is a set of methods aided to un-complicate the workflow of clothing the digital character

RECREATING AND SIMULATING DIGITAL COSTUMES FROM A STAGE PRODUCTION OF \u3ci\u3eMEDEA\u3c/i\u3e

This thesis investigates a technique to effectively construct and simulate costumes from a stage production Medea, in a dynamic cloth simulation application like Maya\u27s nDynamics. This was done by using data collected from real-world fabric tests and costume construction in the theatre\u27s costume studio. Fabric tests were conducted and recorded, by testing costume fabrics for drape and behavior with two collision objects. These tests were recreated digitally in Maya to derive appropriate parameters for the digital fabric, by comparing with the original reference. Basic mannequin models were created using the actors\u27 measurements and skeleton-rigged to enable animation. The costumes were then modeled and constrained according to the construction process observed in the costume studio to achieve the same style and stitch as the real costumes. Scenes selected and recorded from Medea were used as reference to animate the actors\u27 models. The costumes were assigned the parameters derived from the fabric tests to produce the simulations. Finally, the scenes were lit and rendered out to obtain the final videos which were compared to the original recordings to ascertain the accuracy of simulation. By obtaining and refining simulation parameters from simple fabric collision tests, and modeling the digital costumes following the procedures derived from real-life costume construction, realistic costume simulation was achieved

Resolution independent curved seams in clothing animation using a regular particle grid

We present a method for representing seams in clothing animation, and its application in simulation level of detail. Specifically we consider cloth represented as a regular grid of particles connected by spring-dampers, and a seam specified by a closed set of parametric trim curves in the cloth domain. Conventional cloth animation requires the tessellation of seams so that they are handled uniformly by the dynamics process. Our goal is a seam definition which does not constrain the attached clothing panels to be of the same resolution, or even constant resolution, while not being a hindrance to the dynamics process. We also apply our seams to cloth defined on a regular grid, as opposed to the irregular meshes commonly used with seams. The determination of particles interior to the cloth panel can be done using wellknown graphics operations such as scan-conversion. Due to the particle-based nature of the simulation, the dynamics approach combines easily with existing implicit and explicit methods. Finally, because the seams are resolution independent, the particle density per clothing panel can be adjusted as desired. This gives rise to a simple application of the given seams approach illustrating how it may be used for simulation level of detail