Arbitrary Engineering of Spatial Caustics with 3D-printed Metasurfaces

Caustics occur in diverse physical systems, spanning the nano-scale in electron microscopy to astronomical-scale in gravitational lensing. As envelopes of rays, optical caustics result in sharp edges or extended networks. Caustics in structured light, characterized by complex-amplitude distributions, have innovated numerous applications including particle manipulation, high-resolution imaging techniques, and optical communication. However, these applications have encountered limitations due to a major challenge in engineering caustic fields with customizable propagation trajectories and in-plane intensity profiles. Here, we introduce the compensation phase via 3D-printed metasurfaces to shape caustic fields with curved trajectories in free space. The in-plane caustic patterns can be preserved or morphed from one structure to another during propagation. Large-scale fabrication of these metasurfaces is enabled by the fast-prototyping and cost-effective two-photon polymerization lithography. Our optical elements with the ultra-thin profile and sub-millimeter extension offer a compact solution to generating caustic structured light for beam shaping, high-resolution microscopy, and light-matter-interaction studies

Fluids real-time rendering

In this thesis the existing methods for realistic visualization of uids in real-time are reviewed. The correct handling of the interaction of light with a uid surface can highly increase the realism of the rendering, therefore method for physically accurate rendering of re ections and refractions will be used. The light- uid interaction does not stop at the surface, but continues inside the uid volume, causing caustics and beams of light. The simulation of uids require extremely time-consuming processes to achieve physical accuracy and will not be explored, although the main concepts will be given. Therefore, the main goals of this work are: Study and review the existing methods for rendering uids in realtime. Find a simpli ed physical model of light interaction, because a complete physically correct model would not achieve real-time. Develop an application that uses the found methods and the light interaction model

A Survey of Ocean Simulation and Rendering Techniques in Computer Graphics

This paper presents a survey of ocean simulation and rendering methods in computer graphics. To model and animate the ocean's surface, these methods mainly rely on two main approaches: on the one hand, those which approximate ocean dynamics with parametric, spectral or hybrid models and use empirical laws from oceanographic research. We will see that this type of methods essentially allows the simulation of ocean scenes in the deep water domain, without breaking waves. On the other hand, physically-based methods use Navier-Stokes Equations (NSE) to represent breaking waves and more generally ocean surface near the shore. We also describe ocean rendering methods in computer graphics, with a special interest in the simulation of phenomena such as foam and spray, and light's interaction with the ocean surface

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

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

Fluids real-time rendering

In this thesis the existing methods for realistic visualization of uids in real-time are reviewed. The correct handling of the interaction of light with a uid surface can highly increase the realism of the rendering, therefore method for physically accurate rendering of re ections and refractions will be used. The light- uid interaction does not stop at the surface, but continues inside the uid volume, causing caustics and beams of light. The simulation of uids require extremely time-consuming processes to achieve physical accuracy and will not be explored, although the main concepts will be given. Therefore, the main goals of this work are: Study and review the existing methods for rendering uids in realtime. Find a simpli ed physical model of light interaction, because a complete physically correct model would not achieve real-time. Develop an application that uses the found methods and the light interaction model

Exploration of Mouth Shading and Lighting in CG Production

The lighting and shading of human teeth in current computer animation features and live-action movies with effects are often intentionally avoided or processed by simple methods since they interact with light in complex ways through their intricate layered structure. The semi-translucent appearance of natural human teeth which result from subsurface scattering is difficult to replicate in synthetic scenes, though two techniques are often implemented. The first technique is to create an anatomically correct layered model, and render the teeth with both theoretically and empirically derived optical parameters of human teeth using physical subsurface materials. The second technique largely takes advantage of visual cheating, achieved by irradiance blending of finely painted textures. The result visually confirms that for most situations, non-physically based shading can yield believable rendered teeth by finely controlling contribution layers. In particular situations, such as an extremely close shot of a mouth, however, a physically correct shading model is necessary to produce highly translucent and realistic teeth

Ray Tracing Gems

This book is a must-have for anyone serious about rendering in real time. With the announcement of new ray tracing APIs and hardware to support them, developers can easily create real-time applications with ray tracing as a core component. As ray tracing on the GPU becomes faster, it will play a more central role in real-time rendering. Ray Tracing Gems provides key building blocks for developers of games, architectural applications, visualizations, and more. Experts in rendering share their knowledge by explaining everything from nitty-gritty techniques that will improve any ray tracer to mastery of the new capabilities of current and future hardware. What you'll learn: The latest ray tracing techniques for developing real-time applications in multiple domains Guidance, advice, and best practices for rendering applications with Microsoft DirectX Raytracing (DXR) How to implement high-performance graphics for interactive visualizations, games, simulations, and more Who this book is for: Developers who are looking to leverage the latest APIs and GPU technology for real-time rendering and ray tracing Students looking to learn about best practices in these areas Enthusiasts who want to understand and experiment with their new GPU

Validation of 3d radiative transfer in coastal-ocean water systems as modeled by DIRSIG

The radiative transfer equation (RTE) is a mathematical description of radiative gains and losses experienced by a propagating electromagnetic wave in a participating medium. Except for an isotropic lossless vacuum, all other volumes have the potential to scatter, absorb and emit radiant energy. Of these possible events, the global scattering term is the greatest obstacle between a radiative transfer problem and its solution. Historically, the RTE has been solved using a host of analytical approximations and numerical methods. Typical solution models exploit plane-parallel assumptions where it is assumed that optical properties may vary vertically with depth, but have an infinite horizontal extent. For more complicated scenarios that include pronounced 3D variability, a Monte Carlo statistical approach to the radiative transfer solution is often utilized. This statistical approach has been integrated within the Digital Imaging and Remote Sensing Image Generation (DIRSIG) model in the form of photon mapping. Photon mapping provides a probabilistic solution to the in-scattered radiance problem, by employing a two-pass technique that first populates a photon map based on a Monte Carlo solution to the global scattering term, and then later uses this map to reconstruct the in-scattered radiance distribution during a traditional raytracing pass. As with any computational solution, the actual implementation of the technique requires assumptions, simplifications and integration within a cohesive rendering model. Moreover, the realistic simulation of any environment requires several other radiometric solutions that are not directly related to the photon mapped in-scattered radiance. This research attempts to validate raytraced and photon mapped contributions to sensor reaching radiance that can be expected in typical littoral environments, including boundary interface, medium and submerged or floating object effects. This is accomplished by comparing DIRSIG modeled results to those predicted analytically, by comparison to other numerical models, and by comparison to observed field phenomenology. When appropriate, first-order estimates of a computational solution\u27s ability to render a given phenomenon are provided, including any variance or bias that may result as a function of the user-specified solution configuration

Ray-traced simulation of radiation pressure for optical lift

When light refracts at a surface, it changes the direction and intensity of the light rays. By Newton\u27s 3rd law, this process imparts a small momentum to the object. This effect can be exploited to manipulate very small objects, by carefully selecting the shape and optical properties of the object. This thesis describes a computational model based on the laws of physics to determine the forces and torques resulting from light interacting with a hemicylindrical particle. This model has been successfully used to predict for the first time a phenomenon called optical lift