Natalya Tatarchuk

Dynamic parallax occlusion mapping with approximate soft shadows

This paper presents a per-pixel ray tracing algorithm with dynamic lighting of surfaces in real-time on the GPU. First, we propose a method for increased precision of the critical ray-height field intersection and adaptive height field sampling. We achieve higher quality results than the existing inverse displacement mapping algorithms. Second, soft shadows are computed by estimating light visibility for the displaced surfaces. Third, we describe an adaptive level-of-detail system which uses the information supplied by the graphics hardware during rendering to automatically manage shader complexity. This LOD scheme maintains smooth transitions between the full displacement computation and a simplified representation at a lower level of detail without visual artifacts. The algorithm performs well for animated objects and supports dynamic rendering of height fields for a variety of interesting displacement effects. The presented method is scalable for a range of consumer grade GPU products. It exhibits a low memory footprint and can be easily integrated into existing art pipelines for games and effects rendering.

Real-time mesh simplification using the GPU

Recent advances in real-time rendering have allowed the GPU implementation of traditionally CPU-restricted algorithms, often with performance increases of an order of magnitude or greater. Such gains are achieved by leveraging the large-scale parallelism of the GPU towards applications that are well-suited for these streaming architectures. By contrast, mesh simplification has traditionally been viewed as a non-interactive process not readily amenable to GPU acceleration. We demonstrate how it becomes practical for real-time use through our method, and that the use of the GPU even for offline simplification leads to significant increases in performance. Our approach for mesh decimation adopts a vertex-clustering method to the GPU by taking advantage of a new addition to the rendering pipeline - the geometry shader stage. We present a novel general-purpose data structure designed for streaming architectures called the probabilistic octree, which allows for much of the flexibility of offline implementations, including sparse encoding and variable level-of-detail. We demonstrate successful use of this data structure in our GPU implementation of mesh simplification. We can generate adaptive levels of detail by applying non-linear warping functions to the cluster map in order to improve resulting simplification quality. Our GPU-accelerated approach enables simultaneous construction of multiple levels of detail and out-of-core simplification of extremely large polygonal meshes.

March of the Froblins: simulation and rendering massive crowds of intelligent and detailed creatures on GPU

Artificial intelligence (AI) is generally considered to be one of the key components of a computer game. Sometimes when we play a game, we may wish that the computer opponents were written better. At those times while playing against the computer, we feel that the game is unbalanced. Perhaps the computer player has been given different set of rules, or uses the same rules, but has more resources (health, weapons, etc.). The complexity of underlying AI systems, along with game design, belies the resulting feeling we have when playing any game. As the CPU and GPU speed and power continues to grow, along with increasing memory amounts and bandwidth, game developers are constantly improving the graphics of their games. In the last five years the production quality of games has been increasing (along with the corresponding budgets). Recent games woo players with incredible breakthroughs in real- time 3D graphics, complexity of the worlds and characters, as well as various post-processing effects. And while there had been tremendous improvements for parallelizing rendering through the evolution of consumer GPU pipelines, artificial intelligence computations are treading behind. To date, there had been rather few attempts at parallelizing AI computations.

Real-Time Isosurface Extraction Using the GPU Programmable Geometry Pipeline

Figure 1. We show the result of extracting a series of highly detailed isosurfaces at interactive rates. Our system implements a hybrid cubes-tetrahedra method, which leverages the strengths of each as applicable to the unique architecture of the GPU. The left pair of images (wireframe and shaded, using a base cube grid of 64) show only an extracted isosurface, while the right pair displays an alternate isosurface overlayed with a volume rendering.

Advanced interactive medical visualization on the GPU

Interactive visual analysis of a patients anatomy by means of computer-generated 3D imagery is crucial for diagnosis, pre-operative planning, and surgical training. The task of visualization is no longer limited to producing images at interactive rates, but also includes the guided extraction of significant features to assist the user in the data exploration process. An effective visualization module has to perform a problem-specific abstraction of the dataset, leading to a more compact and hence more efficient visual representation. Moreover, many medical applications, such as surgical training simulators and pre-operative planning for plastic and reconstructive surgery, require the visualization of datasets that are dynamically modified or even generated by a physics-based simulation engine. In this paper we present a set of approaches that allow interactive exploration of medical datasets in real time. Our method combines direct volume rendering via ray-casting with a novel approach for isosurface extraction and re-use directly on graphics processing units (GPUs) in a single framework. The isosurface extraction technique takes advantage of the recently introduced Microsoft DirectX^(R)10 pipeline for dynamic surface extraction in real time using geometry shaders. This surface is constructed in polygonal form and can be directly used post-extraction for collision detection, rendering, and optimization. The resulting polygonal surface can also be analyzed for geometric properties, such as feature area, volume and size deviation, which is crucial for semi-automatic tumor analysis as used, for example, in colonoscopy. Additionally, we have developed a technique for real-time volume data analysis by providing an interactive user interface for designing material properties for organs in the scanned volume. Combining isosurface with direct volume rendering allows visualization of the surface properties as well as the context of tissues surrounding the region and gives better context for navigation. Our application can be used with CT and MRI scan data, or with a variety of other medical and scientific applications. The techniques we present are general and intuitive to implement and can be used for many other interactive environments and effects, separately or together.

Practical parallax occlusion mapping with approximate soft shadows for detailed surface rendering

(a) (b) Figure 1. Realistic city scene rendered using parallax occlusion mapping applied to the cobblestone sidewalk in (a) and using the normal mapping technique in (b).

A system for rapid, automatic shader level-of-detail

Level-of-detail (LOD) rendering is a key optimization used by modern video game engines to achieve high-quality rendering with fast performance. These LOD systems require simplified shaders, but generating simplified shaders remains largely a manual optimization task for game developers. Prior efforts to automate this process have taken hours to generate simplified shader candidates, making them impractical for use in modern shader authoring workflows for complex scenes. We present an end-to-end system for automatically generating a LOD policy for an input shader. The system operates on shaders used in both forward and deferred rendering pipelines, requires no additional semantic information beyond input shader source code, and in only seconds to minutes generates LOD policies (consisting of simplified shader, the desired LOD distance set, and transition generation) with performance and quality characteristics comparable to custom hand-authored solutions. Our design contributes new shader simplification transforms such as approximate common subexpression elimination and movement of GPU logic to parameter bind-time processing on the CPU, and it uses a greedy search algorithm that employs extensive caching and upfront collection of input shader statistics to rapidly identify simplified shaders with desirable performance-quality trade-offs.

Advances in real-time rendering in 3D graphics and games II

Advances in real-time graphics research and the increasing power of mainstream GPUs has generated an explosion of innovative algorithms suitable for rendering complex virtual worlds at interactive rates. Every year, the latest video games display a vast variety of sophisticated algorithms that power ground-breaking 3D rendering and push the visual boundaries and interactive experience of rich environments. This course covers a series of topics on the best practices and techniques prevalent in state-of-the-art rendering in several award-winning games, and describes innovative and practical 3D rendering research breaktrhoughs that will be used in the games of tomorrow. The course is designed for technical practitioners and developers of graphics engines for visualization, games, or effects rendering. Presented techniques are applicable in real-time and off-line domains. Attendees will acquire a number of highly optimized algorithms in various areas of real-time rendering.

Practical dynamic parallax occlusion mapping

We present an improved parallax occlusion mapping algorithm for dynamic real-time lighting of surfaces including soft shadows, a directable LOD system and increased precision of the critical height field-ray intersection computation. We simulate the effects of motion parallax with perspective-correct depth at any viewing angle. Per-pixel ray intersections of a height field with view and light directions are performed to determine correct displacement on the surface as well as its visibility.

RenderMonkey: an effective environment for shader prototyping and development

We present a new process for real-time shader development using an improved environment for shader content creation—the RenderMonkey IDE. This environment enables anyone with an interest in real-time graphics to quickly embrace programmable shaders for projects from game engines to scientific visualization or anything in between. The RenderMonkey IDE is a general tool for effective shader development, allowing collaboration between artists and programmers in a single, unified environment. We will present the design philosophy behind the RenderMonkey IDE, the process for shader development, and new methodologies for integrating RenderMonkey into pre-existing production pipelines.