10,397 research outputs found
Stop-and-go cloth draping
The aim of cloth draping is to compute the rest state of a piece of cloth, possibly in contact with other solid objects, as quickly as possible. The context of free motion and very large deformations specific to cloth simulation makes the usual energy minimization schemes traditionally used in mechanical engineering inefficient. Therefore, most cloth draping applications only rely on dynamic simulation with ad hoc viscous damping or the dissipative behavior of numerical integration methods for obtaining convergence to the rest position of the cloth. We propose a "stop-and-go” technique which cuts out the velocity of the object at particular times for converging to the rest state, while taking advantage of the natural cloth motion toward equilibrium. This scheme can very easily complement any existing dynamical cloth simulation system, using either implicit or explicit numerical integration method
Smarticles: A Method for Identifying and Correcting Instability and Error Caused by Explicit Integration Techniques in Physically Based Simulations
Using an explicit integration method in physically based animations has many advantages including conceptual and computational simplicity, however, it re- quires small time steps to ensure low numerical instability. Simulations with large numbers of individually interacting components such as cloth, hair, and fluid models, are limited by the sections of particles most susceptible to error. This results in the need for smaller time steps than required for the majority of the system. These sections can be diverse and dynamic, quickly changing in size and location based on forces in the system. Identifying and handling these trou- blesome sections could allow for a larger time step to be selected, while preventing a breakdown in the simulation.
This thesis presents Smarticles (smart particles), a method of individually de- tecting particles exhibiting signs of instability and stabilizing them with minimal adverse effects to visual accuracy. As a result, higher levels of error introduced from large time steps can be tolerated with minimal overhead. Two separate approaches to Smarticles were implemented. They attempt to find oscillating particles by analyzing a particle’s (1) past behavior and (2) behavior with re- spect to its neighbors along a strand. Both versions of Smarticles attempt to correct unstable particles using velocity dampening. Smarticles was applied to a two dimensional hair simulation modeled as a continuum using smooth particle hydrodynamic. Hair strands are formed by linking particles together using one of two methods: position based dynamics or mass-spring forces.
Both versions of Smarticles, as well as a control of normal particles, were directly compared and evaluated based on stability and visual fluidity. Hair particles were exposed to various forms of external forces under increasing time step lengths. Testing showed that both versions of Smarticles working together allowed an average increase of 18.62% in the time step length for hair linked with position based dynamics. In addition, Smarticles was able to significantly reduce visible instability at even larger time steps. While these results suggest Smarticles is successful, the method used to correct particle instability may jeopardize other important aspects of the simulation. A more accurate correction method would likely need to be developed to make Smarticles an advantageous method
From early draping to haute couture models: 20 years of research
Simulating the complex fashion garments of haute couture can only be reached through an optimal combination of modeling techniques and numerical methods that combines high computation efficiency with the versatility required for simulating intricate garment designs. Here we describe optimal choices illustrated by their integration into a design and simulation tool that allow interactive prototyping of garments along drape motion and comfortability tests on animated postures. These techniques have been successfully used to bring haute couture garments from early draping of fashion designers, to be simulated and visualized in the virtual worl
DiffCloth: Differentiable Cloth Simulation with Dry Frictional Contact
Cloth simulation has wide applications in computer animation, garment design,
and robot-assisted dressing. This work presents a differentiable cloth
simulator whose additional gradient information facilitates cloth-related
applications. Our differentiable simulator extends a state-of-the-art cloth
simulator based on Projective Dynamics (PD) and with dry frictional contact. We
draw inspiration from previous work to propose a fast and novel method for
deriving gradients in PD-based cloth simulation with dry frictional contact.
Furthermore, we conduct a comprehensive analysis and evaluation of the
usefulness of gradients in contact-rich cloth simulation. Finally, we
demonstrate the efficacy of our simulator in a number of downstream
applications, including system identification, trajectory optimization for
assisted dressing, closed-loop control, inverse design, and real-to-sim
transfer. We observe a substantial speedup obtained from using our gradient
information in solving most of these applications
A review of solar collectors and thermal energy storage in solar thermal applications
Thermal applications are drawing increasing attention in the solar energy research field, due to their high performance in energy storage density and energy conversion efficiency. In these applications, solar collectors and thermal energy storage systems are the two core components. This paper focuses on the latest developments and advances in solar thermal applications, providing a review of solar collectors and thermal energy storage systems. Various types of solar collectors are reviewed and discussed, including both non-concentrating collectors (low temperature applications) and concentrating collectors (high temperature applications). These are studied in terms of optical optimisation, heat loss reduction, heat recuperation enhancement and different sun-tracking mechanisms. Various types of thermal energy storage systems are also reviewed and discussed, including sensible heat storage, latent heat storage, chemical storage and cascaded storage. They are studied in terms of design criteria, material selection and different heat transfer enhancement technologies. Last but not least, existing and future solar power stations are overviewed.Peer reviewe
The analysis of Blender open-source software cloth simulation capabilities
This article explores Blender open-source software capabilities in the area of cloth simulations. Simulation performance with different scene complexity and quality settings is tested with a script that automates the testing. System resource utilization is measured and the appearance of visual artifacts is taken into consideration. Cloth simulation features of Blender are compared to commercial software
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