Interactive volume rendering of large fields

We first present the volume-rendering pipeline and the most typical of the existing methods for each pipeline stage. The complexity of each stage in terms of computing time is analyzed for each method. Then the demands and the scope of interactive volume rendering are briefly summarized. Based on this analysis we examine alternate solutions to optimize each pipeline stage in order to allow interactive visualization while maintaining the image quality. The proposed method maximizes interactive manipulation possibilities and minimizes runtimes by sampling at the Nyquist rate and by flexibly trading off quality for performance at any pipeline level. Our approach is suitable for rendering large, scalar, discrete volume fields such as semitransparent clouds (or X-rays) on the fly.     

Interactive texture-based volume rendering for large data sets

To employ direct volume rendering, TRex uses parallel graphics hardware, software-based compositing, and high-performance I/O to provide near-interactive display rates for time-varying, terabyte-sized data sets. We present a scalable, pipelined approach for rendering data sets too large for a single graphics card. To do so, we take advantage of multiple hardware rendering units and parallel software compositing. The goals of TRex, our system for interactive volume rendering of large data sets, are to provide near-interactive display rates for time-varying, terabyte-sized uniformly sampled data sets and provide a low-latency platform for volume visualization in immersive environments. We consider 5 frames per second (fps) to be near-interactive rates for normal viewing environments and immersive environments to have a lower bound frame rate of l0 fps. Using TRex for virtual reality environments requires low latency - around 50 ms per frame or 100 ms per view update or stereo pair. To achieve lower latency renderings, we either render smaller portions of the volume on more graphics pipes or subsample the volume to render fewer samples per frame by each graphics pipe. Unstructured data sets must be resampled to appropriately leverage the 3D texture volume rendering method     

An efficient rendering method for large vector data on large terrain models

This paper presents an efficient way to render large-scale vector maps on level-of-detail(LOD) digital elevation models(DEMs).By using the frame buffer and Voronoi diagram,we achieve a rapid simplification of large-scale vector maps while keeping their original topological relationships.With the simplified maps,we establish level-of-detail vector map models.In the detailed level,we use the stencil shadow volume approach to render the map accurately,and in the coarse level we use substitute techniques to ren...     

Interactive display of large solid models for walkthroughs

A new paradigm for designing complex engineering systems has emerged from computer graphics and CAD/CAM technology. Virtual design environments allow users to design and visualize all stages of the product. They not only free designers from the two dimensions of pencil and paper but also eliminate costly construction of physical mock-ups. We are developing the necessary technology for interactive walkthroughs of large mechanical and architectural models. This development includes model construction, display and interfacing with high-performance graphics systems and immersive technologies. Our ultimate goal is to create an environment where users will explore the complete model of a large design, such as a submarine, and verify that all constraints are satisfied in the same way they would a real one-by walking around in it. In applying our approach to a submarine storage and handling system model, we improved the overall frame rate by three to four times compared with rendering the polygonal B-rep. The online triangulation allows us to spend our rendering resources in the parts of the model significant for the current image. The overall system is currently being applied to large CAD models like submarines and fighting vehicles     

Interactive display of large NURBS models

We present algorithms for interactive rendering of large-scale NURBS models. The algorithms convert the NURBS surfaces to Bezier surfaces, tessellate each Bezier surface into triangles, and render them using the triangle-rendering capabilities common to current graphics systems. We present algorithms for computing tight bounds on surface properties in order to generate high quality tessellation of Bezier surfaces. We introduce enhanced visibility determination techniques and present methods to make efficient use of coherence between successive frames. In addition, we also discuss issues in parallelization of these techniques. The algorithm also avoids polygonization anomalies like cracks. Our algorithms work well in practice and, on high-end graphics systems, are able to display models described using thousands of Bezier surfaces at interactive frame rates     

交互式实时水面渲热

介绍了一种利用可编程图形硬件来实现水面实时渲染的方法。该渲染过程分为两个阶段,即水面建模和光照实现。通过当前图形硬件新提供的顶点纹理技术来对水面进行建模,并结合环境纹理映射技术和二维纹理映射技术实现了水面上的反射与折射等光照现象。实验证明,该方法大大提高了渲染速度,增强了水面渲染的交互性和实时性。     

Interactive view-dependent rendering over networks

For a client-server based view-dependent rendering system, the overhead of view-dependent rendering and the network latency are major obstacles in achieving interactivity. In this paper, we first present a multiresolution hierarchy traversal management strategy to control the overhead of view-dependent rendering for low-capacity clients. Then we propose a predictive parallel strategy to overcome the network latency for client-server based view-dependent multiresolution rendering systems. Our solution is to make the client process and the server process run in parallel, using the rendering time to cover the network latency. For networks with long round-trip times, we manage to overlap the network latency for one frame with the rendering time for multiple frames. View-parameters prediction is incorporated to make the parallelism of the client and the server feasible. In order to maintain an acceptable view-dependent rendering quality in the network environment, we develop a synchronization mechanism and a dynamic adjustment mechanism to handle the transient network slowdowns and the changes of the network condition. Our experimental results, in comparison with the sequential method, show that our predictive parallel approach can achieve an interactive frame rate while keeping an acceptable rendering quality for large triangle models over networks with relatively long round-trip times.     

Interactive GPU-based adaptive cartoon-style rendering

In this paper we present a novel real-time cartoon-style rendering approach, which targets very large meshes. Cartoon drawing usually uses a limited number of colors for shading and emphasizes special effects, such as sharp curvature and silhouettes. It also paints the remaining large regions with uniform solid colors. Our approach quantizes light intensity to generate different shadow colors and utilizes multiresolution mesh hierarchy to maintain appropriate levels of detail across various regions of the mesh. To comply with visual requirements, our algorithm exploits graphics hardware programmability to draw smooth silhouette and color boundaries within the vertex and fragment processors. We have adopted a simplification scheme that executes simplification operators without incurring extra simplification operations as a precondition. The real-time refinement of the mesh, which is performed by the graphics processing unit (GPU), dramatically improves image quality and reduces CPU load.     

Interactive rendering of dynamic geometry

Fluid simulations typically produce complex three-dimensional (3D) isosurfaces whose geometry and topology change over time. The standard way of representing such "dynamic geometry" is by a set of isosurfaces that are extracted individually at certain time steps. An alternative strategy is to represent the whole sequence as a four-dimensional (4D) tetrahedral mesh. The iso-surface at a specific time step can then be computed by intersecting the tetrahedral mesh with a 3D hyperplane. This not only allows the animation of the surface continuously over time without having to worry about the topological changes, but also enables simplification algorithms to exploit temporal coherence. We show how to interactively render such 4D tetrahedral meshes by improving previous GPU-accelerated techniques and building an out-of-core multi-resolution structure based on quadric error simplification. As a second application, we apply our framework to time-varying surfaces that result from morphing one triangle mesh into another.     

交互式实时水面渲染*

介绍了一种利用可编程图形硬件来实现水面实时渲染的方法。该渲染过程分为两个阶段,即水面建模和光照实现。通过当前图形硬件新提供的顶点纹理技术来对水面进行建模,并结合环境纹理映射技术和二维纹理映射技术实现了水面上的反射与折射等光照现象。实验证明,该方法大大提高了渲染速度,增强了水面渲染的交互性和实时性。     

Interactive rendering of NURBS surfaces

NURBS (Non-uniform rational B-splines) surfaces are one of the most useful primitives employed for high quality modeling in CAD/CAM tools and graphics software. Since direct evaluation of NURBS surfaces on the GPU is a highly complex task, the usual approach for rendering NURBS is to perform the conversion into Bézier surfaces on the CPU, and then evaluate and tessellate them on the GPU. In this paper we present a new proposal for rendering NURBS surfaces directly on the GPU in order to achieve interactive and real-time rendering. Our proposal, Rendering Pipeline for NURBS Surfaces (RPNS), is based on a new primitive KSQuad that uses a regular and flexible processing of NURBS surfaces, while maintaining their main geometric properties to achieve real-time rendering. RPNS performs an efficient adaptive discretization to fine tune the density of primitives needed to avoid cracks and holes in the final image, applying an efficient non-recursive evaluation of the basis function on the GPU. An implementation of RPNS using current GPUs is presented, achieving real-time rendering rates of complex parametric models. Our experimental tests show a performance several orders of magnitude higher than traditional approximations based on NURBS to Bézier conversion.     

Interactive volume rendering of large sparse data sets using adaptive mesh refinement hierarchies

In this paper, we present an algorithm that accelerates 3D texture-based volume rendering of large, sparse data sets, i.e., data sets where only a traction of the voxels contain relevant information. In texture-based approaches, the rendering performance is affected by the fill-rate, the size of texture memory, and the texture I/O bandwidth. For sparse data, these limitations can be circumvented by restricting most of the rendering work to the relevant parts of the volume. In order to efficiently enclose the corresponding regions with axis-aligned boxes, we employ a hierarchical data structure, known as an AMR (adaptive mesh refinement) tree. The hierarchy is generated utilizing a clustering algorithm. A good balance is thereby achieved between the size of the enclosed volume, i.e., the amount to render in graphics hardware and the number of axis-aligned regions, i.e., the number of texture coordinates to compute in software. The waste of texture memory by the power-of-two restriction is minimized by a 3D packing algorithm which arranges texture bricks economically in memory. Compared to an octree approach, the rendering performance is significantly increased and less parameter tuning is necessary.     

Optical models for direct volume rendering

This tutorial survey paper reviews several different models for light interaction with volume densities of absorbing, glowing, reflecting, and/or scattering material. They are, in order of increasing realism, absorption only, emission only, emission and absorption combined, single scattering of external illumination without shadows, single scattering with shadows, and multiple scattering. For each model the paper provides the physical assumptions, describes the applications for which it is appropriate, derives the differential or integral equations for light transport, presents calculation methods for solving them, and shows output images for a data set representing a cloud. Special attention is given to calculation methods for the multiple scattering model     

Interactive stereoscopic rendering of volumetric environments

We present an efficient stereoscopic rendering algorithm supporting interactive navigation through large-scale 3D voxel-based environments. In this algorithm, most of the pixel values of the right image are derived from the left image by a fast 3D warping based on a specific stereoscopic projection geometry. An accelerated volumetric ray casting then fills the remaining gaps in the warped right image. Our algorithm has been parallelized on a multiprocessor by employing effective task partitioning schemes and achieved a high cache coherency and load balancing. We also extend our stereoscopic rendering to include view-dependent shading and transparency effects. We have applied our algorithm in two virtual navigation systems, flythrough over terrain and virtual colonoscopy, and reached interactive stereoscopic rendering rates of more than 10 frames per second on a 16-processor SGI challenge.     

面向具有重复结构的大规模CAD模型的快速渲染

目的 基于普通个人计算机快速渲染大规模计算机辅助设计（CAD）模型仍然是个挑战。针对由少量基本对象按一定规律排布而成的大规模CAD模型——重复结构CAD模型,提出一种快速渲染方法,能够在个人计算机上的快速渲染大规模重复结构CAD模型。方法 该方法首先利用重复结构CAD模型的层次结构特征,结合现代GPU的Render-To-Texture的功能进行快速视锥裁剪,节约视锥裁剪时间;然后利用重复结构CAD模型中对象按规律布置的特点,仅对少量基本对象进行面片化,其他对象的面片模型在渲染时根据对象排布规律由基本对象的面片模型实时变换生成,解决大规模CAD模型内存需求过多的问题。结果 基于超级蒙卡核模拟软件系统SuperMC,使用典型重复结构模型——HM（hoogenboom-martin）、ADS（accelerator driven sub-critical system）、DCA（deuterium critical assembly）全堆芯CAD模型进行测试,HM、ADS、DCA模型分别由1 114 384,113 952和20 808个实体组成。测试结果表明,裁剪算法能大幅减少待渲染对象数量,渲染速度明显提高,且模型规模越大,本文方法优势越明显,在远视角的情况下提升效果最为突出,能提升3倍左右;结论 针对任意大规模CAD模型的快速渲染仍然是一个挑战,但本文针对重复结构CAD模型的特点,针对性地提出一套专用渲染策略,在个人计算机上实现大规模重复结构CAD模型的快速渲染。使用多个典型重复结构模型——反应堆全堆芯模型进行测试,测试结果表明了本文方法的有效性。     

Interactive space deformation with hardware-assisted rendering

The authors introduce a new approach for the deformation of surface and raster models in two and three dimensions. Rather than deforming the model, they deform the agents employed to render it. The method uses one deformation tool (the deflector) to deform any object that is ray traceable. Based on deforming the rendering primitives rather than objects, the approach invests computation effort only in those regions of the model that contribute to the final image     

基于GPU的点模型实时绘制

近几年随着GPU的可编程能力的增强,很多基于点的绘制算法都可以移植到GPU上来实现,这样既可以让CPU有时间来处理其他事,又可以通过GPU提高算法的运行速度。由于目前的GPU不支持epsilon-z-buffering算法,大部分基于GPU的绘制算法都是通过Multi-pass绘制来达到较高的绘制质量。然而,这些算法需要在第一和第二个pass中光栅化大量的可能可见的面圆,并在第二个pass的像素shader中对这些可能可见的面圆进行大量的计算。本文提出了一种基于GPU的改进Multi-pass绘制算法,与前面的Multi-pass算法相比,我们的算法只需在第一个pass中对大量可能可见的面圆进行光栅化和深度测试后,便可求出所有可见面圆,即离视点最近的面圆。然后在第二个pass中只对这些可见面圆进行光栅化和逐像素计算,从而避免了大量不必要的计算。     

Interactive point-based rendering of higher-order tetrahedral data

Computational simulations frequently generate solutions defined over very large tetrahedral volume meshes containing many millions of elements. Furthermore, such solutions may often be expressed using non-linear basis functions. Certain solution techniques, such as discontinuous Galerkin methods, may even produce non-conforming meshes. Such data is difficult to visualize interactively, as it is far too large to fit in memory and many common data reduction techniques, such as mesh simplification, cannot be applied to non-conforming meshes. We introduce a point-based visualization system for interactive rendering of large, potentially non-conforming, tetrahedral meshes. We propose methods for adaptively sampling points from non-linear solution data and for decimating points at run time to fit GPU memory limits. Because these are streaming processes, memory consumption is independent of the input size. We also present an order-independent point rendering method that can efficiently render volumes on the order of 20 million tetrahedra at interactive rates.     

Interactive point-based isosurface exploration and high-quality rendering

We present an efficient point-based isosurface exploration system with high quality rendering. Our system incorporates two point-based isosurface extraction and visualization methods: edge splatting and the edge kernel method. In a volume, two neighboring voxels define an edge. The intersection points between the active edges and the isosurface are used for exact isosurface representation. The point generation is incorporated in the GPU-based hardware-accelerated rendering, thus avoiding any overhead when changing the isovalue in the exploration. We call this method edge splatting. In order to generate high quality isosurface rendering regardless of the volume resolution and the view, we introduce an edge kernel method. The edge kernel upsamples the isosurface by subdividing every active cell of the volume data. Enough sample points are generated to preserve the exact shape of the isosurface defined by the trilinear interpolation of the volume data. By employing these two methods, we can achieve interactive isosurface exploration with high quality rendering.