Strain limiting for clustered shape matching

journal articleIn this paper, we advocate explicit symplectic Euler integration and strain limiting in a shape matching simulation framework. The resulting approach resembles not only previous work on shape matching and strain limiting, but also the recently popular position-based dynamics. However, unlike this previous work, our approach reduces to explicit integration under small strains, but remains stable in the presence of non-linearities

High Performance Algorithms for Counting Collisions and Pairwise Interactions

The problem of counting collisions or interactions is common in areas as computer graphics and scientific simulations. Since it is a major bottleneck in applications of these areas, a lot of research has been carried out on such subject, mainly focused on techniques that allow calculations to be performed within pruned sets of objects. This paper focuses on how interaction calculation (such as collisions) within these sets can be done more efficiently than existing approaches. Two algorithms are proposed: a sequential algorithm that has linear complexity at the cost of high memory usage; and a parallel algorithm, mathematically proved to be correct, that manages to use GPU resources more efficiently than existing approaches. The proposed and existing algorithms were implemented, and experiments show a speedup of 21.7 for the sequential algorithm (on small problem size), and 1.12 for the parallel proposal (large problem size). By improving interaction calculation, this work contributes to research areas that promote interconnection in the modern world, such as computer graphics and robotics.Comment: Accepted in ICCS 2019 and published in Springer's LNCS series. Supplementary content at https://mjsaldanha.com/articles/1-hpc-ssp

Parallelized Incomplete Poisson Preconditioner in Cloth Simulation

Efficient cloth simulation is an important problem for interactive applications that involve virtual humans, such as computer games. A common aspect of many methods that have been developed to simulate cloth is a linear system of equations, which is commonly solved using conjugate gradient or multi-grid approaches. In this paper, we introduce to the computer gaming community a recently proposed preconditioner, the incomplete Poisson preconditioner, for conjugate gradient solvers. We show that the parallelized incomplete Poisson preconditioner (PIPP) performs as well as the current state-of-the-art preconditioners, while being much more amenable to standard thread-level parallelism. We demonstrate our results on an 8-core Apple* Mac* Pro and a 32-core code name Emerald Ridge system

Area and Volume Restoration in Elastically Deformable Solids

This paper describes an improvement of a classical energy-based model to simulate elastically deformable solids. The classical model lacks the ability to prevent the collapsing of solids under influence of external forces, such as user interactions and collision. A thorough explanation is given for the origins of instabilities, and extensions that solve the issues are proposed to the physical model. Within the original framework of the classical model a complete restoration of area and volume is introduced. The improved model is suitable for interactive simulation and can recover from volumetric collapsing, in particular upon large deformation

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

Subdivision Shell Elements with Anisotropic Growth

A thin shell finite element approach based on Loop's subdivision surfaces is proposed, capable of dealing with large deformations and anisotropic growth. To this end, the Kirchhoff-Love theory of thin shells is derived and extended to allow for arbitrary in-plane growth. The simplicity and computational efficiency of the subdivision thin shell elements is outstanding, which is demonstrated on a few standard loading benchmarks. With this powerful tool at hand, we demonstrate the broad range of possible applications by numerical solution of several growth scenarios, ranging from the uniform growth of a sphere, to boundary instabilities induced by large anisotropic growth. Finally, it is shown that the problem of a slowly and uniformly growing sheet confined in a fixed hollow sphere is equivalent to the inverse process where a sheet of fixed size is slowly crumpled in a shrinking hollow sphere in the frictionless, quasi-static, elastic limit.Comment: 20 pages, 12 figures, 1 tabl