216 research outputs found
Interactive simulation and rendering of fluids on graphics hardware
Computational uid dynamics can be used to reproduce the complex motion of fluids for use in computer graphics, but the simulation and rendering are both highly computationally intensive. In the past performing these tasks on the CPU could take many minutes per frame, especially for large scale scenes at high levels of detail, which limited their usage to offline applications such as in film and media. However, using the massive parallelism of GPUs, it is nowadays possible to produce uid visual effects in real time for interactive applications such as games. We present such an interactive simulation using the CUDA GPU computing environment and OpenGL graphics API. Smoothed Particle Hydrodynamics (SPH) is a popular particle-based fluid simulation technique that has been shown to be well suited to acceleration on the GPU. Our work extends an existing GPU-based SPH implementation by incorporating rigid body interaction and rendering. Solid objects are represented using particles to accumulate hydrodynamic forces from surrounding fluid, while motion and collision handling are handled by the Bullet Physics library on the CPU. Our system demonstrates two-way coupling with multiple objects floating, displacing fluid and colliding with each other. For rendering we compare the performance and memory consumption of two approaches, splatting and raycasting, we also describe the visual characteristics of each. In our evaluation we consider a target of between 24 and 30 fps to be sufficient for smooth interaction and aim to determine the performance impact of our new features. We begin by establishing a performance baseline and find that the original system runs smoothly up to 216,000 fluid particles but after introducing rendering this drops to 27,000 particles with the rendering taking up the majority of the frame time in both techniques. We find that the most significant limiting factor to splatting performance to be the onscreen area occupied by fluid while the raycasting performance is primarily determined by the resolution of the 3D texture used for sampling. Finally we find that performing solid interaction on the CPU is a viable approach that does not introduce significant overhead unless solid particles vastly outnumber fluid ones
Real-time Physics Based Simulation for 3D Computer Graphics
Restoration of realistic animation is a critical part in the area of computer graphics. The goal of this sort of simulation is to imitate the behavior of the transformation in real life to the greatest extent. Physics-based simulation provides a solid background and proficient theories that can be applied in the simulation. In this dissertation, I will present real-time simulations which are physics-based in the area of terrain deformation and ship oscillations.
When ground vehicles navigate on soft terrains such as sand, snow and mud, they often leave distinctive tracks. The realistic simulation of such vehicle-terrain interaction is important for ground based visual simulations and many video games. However, the existing research in terrain deformation has not addressed this issue effectively. In this dissertation, I present a new terrain deformation algorithm for simulating vehicle-terrain interaction in real time. The algorithm is based on the classic terramechanics theories, and calculates terrain deformation according to the vehicle load, velocity, tire size, and soil concentration. As a result, this algorithm can simulate different vehicle tracks on different types of terrains with different vehicle properties. I demonstrate my algorithm by vehicle tracks on soft terrain.
In the field of ship oscillation simulation, I propose a new method for simulating ship motions in waves. Although there have been plenty of previous work on physics based fluid-solid simulation, most of these methods are not suitable for real-time applications. In particular, few methods are designed specifically for simulating ship motion in waves. My method is based on physics theories of ship motion, but with necessary simplifications to ensure real-time performance. My results show that this method is well suited to simulate sophisticated ship motions in real time applications
Efficient algorithms for the realistic simulation of fluids
Nowadays there is great demand for realistic simulations in the computer graphics field. Physically-based animations are commonly used, and one of the more complex problems in this field is fluid simulation, more so if real-time applications are the goal. Videogames, in particular, resort to different techniques that, in order to represent fluids, just simulate the consequence and not the cause, using procedural or parametric methods and often discriminating the physical solution.
This need motivates the present thesis, the interactive simulation of free-surface flows, usually liquids, which are the feature of interest in most common applications. Due to the complexity of fluid simulation, in order to achieve real-time framerates, we have resorted to use the high parallelism provided by actual consumer-level GPUs. The simulation algorithm, the
Lattice Boltzmann Method, has been chosen accordingly due to its efficiency and the direct mapping to the hardware architecture because of its local operations.
We have created two free-surface simulations in the GPU: one fully in 3D and another restricted only to the upper surface of a big bulk of fluid, limiting the simulation domain to 2D. We have extended the latter to track dry regions and is also coupled with obstacles in a geometry-independent fashion. As it is restricted to 2D, the simulation loses some features due to the impossibility of simulating vertical separation of the fluid. To account for this we have coupled the surface simulation to a generic particle system with breaking wave conditions; the simulations are totally independent and only the coupling binds the LBM with the chosen particle system.
Furthermore, the visualization of both systems is also done in a realistic way within the interactive framerates; raycasting techniques are used to provide the expected light-related effects as refractions, reflections and caustics. Other techniques that improve the overall detail are also applied as low-level detail ripples and surface foam
Particle based modeling and simulation of natural phenomena
Ankara : The Department of Computer Engineering and the Institute of Engineering and Science of Bilkent University, 2010.Thesis (Ph. D.) -- Bilkent University, 2010.Includes bibliographical references leaves 92-108.This thesis is about modeling and simulation of fluids and cloth-like deformable
objects by the physically-based simulation paradigm. Simulated objects are modeled
with particles and their interaction with each other and the environment is
defined by particle-to-particle forces. We propose several improvements over the
existing particle simulation techniques. Neighbor search algorithms are crucial
for the performance efficiency and robustness of a particle system. We present a
sorting-based neighbor search method which operates on a uniform grid, and can
be parallelizable. We improve upon the existing fluid surface generation methods
so that our method captures surface details better since we consider the relative
position of fluid particles to the fluid surface. We investigate several alternatives
of particle interaction schema (i.e. Smoothed Particle Hydrodynamics, the Discrete
Element Method, and Lennard-Jones potential) for the purpose of defining
fluid-fluid, fluid-cloth, fluid-boundary interaction forces. We also propose a practical
way to simulate knitwear and its interaction with fluids. We employ capillary
pressure–based forces to simulate the absorption of fluid particles by knitwear.
We also propose a method to simulate the flow of miscible fluids. Our particle
simulation system is implement to exploit parallel computing capabilities of the
commodity computers. Specifically, we implemented the proposed methods on
multicore CPUs and programmable graphics boards. The experiments show that
our method is computationally efficient and produces realistic results.Bayraktar, SerkanPh.D
Real-time Water Waves with Wave Particles
This dissertation describes the wave particles technique for simulating water surface waves and two way fluid-object interactions for real-time applications, such as video games. Water exists in various different forms in our environment and it is important to develop necessary technologies to be able to incorporate all these forms in real-time virtual environments. Handling the behavior of large bodies of water, such as an ocean, lake, or pool, has been computationally expensive with traditional techniques even for offline graphics applications, because of the high resolution requirements of these simulations. A significant portion of water behavior for large bodies of water is the surface wave phenomenon. This dissertation discusses how water surface waves can be simulated efficiently and effectively at real-time frame rates using a simple particle system that we call "wave particles." This approach offers a simple, fast, and unconditionally stable solution to wave simulation. Unlike traditional techniques that try to simulate the water body (or its surface) as a whole with numerical techniques, wave particles merely track the deviations of the surface due to waves forming an analytical solution. This allows simulation of seemingly infinite water surfaces, like an open ocean. Both the theory and implementation of wave particles are discussed in great detail. Two-way interactions of floating objects with water is explained, including generation of waves due to object interaction and proper simulation of the effect of water on the object motion. Timing studies show that the method is scalable, allowing simulation of wave interaction with several hundreds of objects at real-time rates
Shallow waters simulation
Dissertação de mestrado integrado em Informatics EngineeringRealistic simulation and rendering of water in real-time is a challenge within the field of computer graphics, as it
is very computationally demanding. A common simulation approach is to reduce the problem from 3D to 2D by
treating the water surface as a 2D heightfield. When simulating 2D fluids, the Shallow Water Equations (SWE)
are often employed, which work under the assumption that the water’s horizontal scale is much greater than it’s
vertical scale.
There are several methods that have been developed or adapted to model the SWE, each with its own advantages
and disadvantages. A common solution is to use grid-based methods where there is the classic approach
of solving the equations in a grid, but also the Lattice-Boltzmann Method (LBM) which originated from the field of
statistical physics. Particle based methods have also been used for modeling the SWE, namely as a variation of
the popular Smoothed-Particle Hydrodynamics (SPH) method.
This thesis presents an implementation for real-time simulation and rendering of a heightfield surface water
volume. The water’s behavior is modeled by a grid-based SWE scheme with an efficient single kernel compute
shader implementation.
When it comes to visualizing the water volume created by the simulation, there are a variety of effects that
can contribute to its realism and provide visual cues for its motion. In particular, When considering shallow water,
there are certain features that can be highlighted, such as the refraction of the ground below and corresponding
light attenuation, and the caustics patterns projected on it.
Using the state produced by the simulation, a water surface mesh is rendered, where set of visual effects are
explored. First, the water’s color is defined as a combination of reflected and transmitted light, while using a Cook-
Torrance Bidirectional Reflectance Distribution Function (BRDF) to describe the Sun’s reflection. These results
are then enhanced by data from a separate pass which provides caustics patterns and improved attenuation
computations. Lastly, small-scale details are added to the surface by applying a normal map generated using
noise.
As part of the work, a thorough evaluation of the developed application is performed, providing a showcase of
the results, insight into some of the parameters and options, and performance benchmarks.Simulação e renderização realista de água em tempo real é um desafio dentro do campo de computação gráfica,
visto que é muito computacionalmente exigente. Uma abordagem comum de simulação é de reduzir o problema
de 3D para 2D ao tratar a superfície da água como um campo de alturas 2D. Ao simular fluidos em 2D, é
frequente usar as equações de águas rasas, que funcionam sobre o pressuposto de que a escala horizontal da
água é muito maior que a sua escala vertical.
Há vários métodos que foram desenvolvidos ou adaptados para modelar as equações de águas rasas, cada
uma com as suas vantagens e desvantagens. Uma solução comum é utilizar métodos baseados em grelhas
onde existe a abordagem clássica de resolver as equações numa grelha, mas também existe o método de Lattice
Boltzmann que originou do campo de física estatística. Métodos baseados em partículas também já foram
usados para modelar as equações de águas rasas, nomeadamente como uma variação do popular método de
SPH.
Esta tese apresenta uma implementação para simulação e renderização em tempo real de um volume de
água com uma superfície de campo de alturas. O comportamento da água é modelado por um esquema de
equações de águas rasas baseado na grelha com uma implementação eficiente de um único kernel de compute
shader.
No que toca a visualizar o volume de água criado pela simulação, existe uma variedade de efeitos que podem
contribuir para o seu realismo e fornecer dicas visuais sobre o seu movimento. Ao considerar águas rasas, existem
certas características que podem ser destacadas, como a refração do terreno por baixo e correspondente
atenuação da luz, e padrões de cáusticas projetados nele.
Usando o estado produzido pela simulação, uma malha da superfície da água é renderizada, onde um conjunto
de efeitos visuais são explorados. Em primeiro lugar, a cor da água é definida como uma combinação de
luz refletida e transmitida, sendo que uma BRDF de Cook-Torrance é usada para descrever a reflexão do Sol.
Estes resultados são depois complementados com dados gerados num passo separado que fornece padrões
de cáusticas e melhora as computações de atenuação. Por fim, detalhes de pequena escala são adicionados à
superfície ao aplicar um mapa de normais gerado com ruído.
Como parte do trabalho desenvolvido, é feita uma avaliação detalhada da aplicação desenvolvida, onde é apresentada
uma demonstração dos resultados, comentários sobre alguns dos parâmetros e opções, e referências
de desempenho
Haptic Interaction with 3D oriented point clouds on the GPU
Real-time point-based rendering and interaction with virtual objects is gaining popularity
and importance as di�erent haptic devices and technologies increasingly provide the basis
for realistic interaction. Haptic Interaction is being used for a wide range of applications
such as medical training, remote robot operators, tactile displays and video games. Virtual
object visualization and interaction using haptic devices is the main focus; this process
involves several steps such as: Data Acquisition, Graphic Rendering, Haptic Interaction
and Data Modi�cation. This work presents a framework for Haptic Interaction using the
GPU as a hardware accelerator, and includes an approach for enabling the modi�cation
of data during interaction. The results demonstrate the limits and capabilities of these
techniques in the context of volume rendering for haptic applications. Also, the use
of dynamic parallelism as a technique to scale the number of threads needed from the
accelerator according to the interaction requirements is studied allowing the editing of
data sets of up to one million points at interactive haptic frame rates
EFFICIENT PARTICLE-BASED VISCOUS FLUID SIMULATION WITH VIDEO-GUIDED REAL-TO-VIRTUAL PARAMETER TRANSFER
Viscous fluids, such as honey and molten chocolate, are common materials frequently seen in our daily life. These viscous fluids exhibit characteristic behaviors. Capturing and understanding such dynamics have been required for various applications. Although recent research made advances in simulating the viscous fluid dynamics, still many challenges are left to be addressed. In this dissertation, I present novel techniques to more efficiently and accurately simulate viscous fluid dynamics and propose a parameter identification framework to facilitate the tedious parameter tuning steps for viscous materials. In fluid simulation, enforcing the incompressibility robustly and efficiently is essential. One known challenge is how to set appropriate boundary conditions for free surfaces and solid boundaries. I propose a new boundary handling approach for an incompressible particle-based solver based on the connectivity analysis for simulation particles. Another challenge is that previously proposed techniques do not scale well. To address this, I propose a new multilevel particle-based solver which constructs the hierarchy of simulation particles. These techniques improve the robustness and efficiency achieving the nearly linear scaling unlike previous approaches. To simulate characteristic behaviors of viscous fluids, such as coiling and buckling phenomena and adhesion to other materials, it is necessary to develop a specialized solver. I propose a stable and efficient particle-based solver for simulating highly viscous fluids by using implicit integration with the full form of viscosity. To simulate more accurate interactions with solid objects, I propose a new two-way fluid-solid coupling method for viscous fluids via the unified minimization. These approaches also improve the robustness and efficiency while generating rotational and sticky behaviors of viscous fluids. One important challenge for the physically-based simulation is that it is not obvious how to choose appropriate material parameters to generate our desirable behaviors of simulated materials. I propose a parameter identification framework that helps to tune material parameters for viscous fluids with example video data captured from real world fluid phenomena. This framework identifies viscosity parameters for the real viscous fluids while estimating the hidden variables for the fluids, and enables the parameter transfer from the real world to virtual environment.Doctor of Philosoph
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