Binary volume rendering using Slice-based Binary Shell

This paper presents a new data structure, Slice-based Binary Shell (SBS), for efficient manipulation and rendering of binary volume data. Since SBS stores only surface voxels with selected attributes of the voxels in a slice-based data structure that allows direct access to the voxels, it shows high storage and computational efficiency. This efficiency becomes more prominent when representing multiple binary objects. We also present an efficient rendering algorithm for SBS. The algorithm, based on the shear-warp technique, provides high-speed interactive rendering for binary volumes of many objects on a PC with no specialized hardware.     

Discrete shading of three-dimensional objects from medial axis transform

In this paper, we present a discrete shading technique using medial axis transform (MAT) of 3D binary image data based on digital generalized octagonal distances. Our method is computationally attractive as it does not require the explicit computation of surface normals. We have compared our results with images rendered from voxel and octree representations while using analytical surface rendered images as bench marks. The quality of rendering by our method is certainly superior to those obtained from voxel and octree representations.     

Real Time, Accurate, Multi-Featured Rendering of Bump Mapped Surfaces

We present a new technique to render in real time objects which have part of their high frequency geometric detail encoded in bump maps. It is based on the quantization of normal-maps, and achieves excellent result both in rendering time and rendering quality, with respect to other alternative methods. The method proposed also allows to add many interesting visual effects, even for object with large bumb maps, including non-s rendering, chrome effects, shading under multiple lights, rendering of different materials within a single object, specular reflections and others. Moreover, the implementation of the method is not complex and can be eased by software reuse.     

Combining estimators for Monte Carlo volume rendering with shading

Monte Carlo volume rendering (MCVR), which allows for generating X-ray like images, offers significant advantages over existing volume rendering techniques in terms of time and memory complexity. The classical shading for MCVR, however, results in a low quality image. In this paper, a so-called estimators combining technique is presented that estimates a realistic rendering using the Lambertian reflection illumination model. Such a technique is particularly adapted to changes in viewing and lighting, and provides high quality shading images exhibiting strong shape and spatial relationship of objects.     

体绘制技术在医学可视化中的新发展

科学计算可视化体绘制算法能反映出体数据的内部信息，在医学，它已经从辅诊断发展成为辅助治疗的重要手段，体可视化技术是医学可视化的重要研究内容，其处理过程包括体数据的获取，模型的建立，数据的映射，绘制等操作，该文介绍了医学可视化中常使用的几种光照模型，针对基于图象空间和对象空间两种体绘制算法，介绍了它们的基本思想方法，并详细阐述了在近期的主要加速技术和提高图象质量方法的新进展，最后给出了实验数据和结论。     

Practical Acquisition of Shape and Plausible Appearance of Reflective and Translucent Objects

We present a practical method for acquisition of shape and plausible appearance of reflective and translucent objects for realistic rendering and relighting applications. Such objects are extremely challenging to scan with existing capture setups, and have previously required complex lightstage hardware emitting continuous illumination. We instead employ a practical capture setup consisting of a set of desktop LCD screens to illuminate such objects with piece-wise continuous illumination for acquisition. We employ phase-shifted sinusoidal illumination for novel estimation of high quality photometric normals and transmission vector along with diffuse-specular separated reflectance/transmission maps for realistic relighting. We further employ neural in-painting to fill gaps in our measurements caused by gaps in screen illumination, and a novel NeuS-based neural rendering that combines these shape and reflectance maps acquired from multiple viewpoints for high-quality 3D surface geometry reconstruction along with plausible realistic rendering of complex light transport in such objects.     

Shape-aware Volume Illustration

We introduce a novel volume illustration technique for regularly sampled volume datasets. The fundamental difference between previous volume illustration algorithms and ours is that our results are shape-aware, as they depend not only on the rendering styles, but also the shape styles. We propose a new data structure that is derived from the input volume and consists of a distance volume and a segmentation volume. The distance volume is used to reconstruct a continuous field around the object boundary, facilitating smooth illustrations of boundaries and silhouettes. The segmentation volume allows us to abstract or remove distracting details and noise, and apply different rendering styles to different objects and components. We also demonstrate how to modify the shape of illustrated objects using a new 2D curve analogy technique. This provides an interactive method for learning shape variations from 2D hand-painted illustrations by drawing several lines. Our experiments on several volume datasets demonstrate that the proposed approach can achieve visually appealing and shape-aware illustrations. The feedback from medical illustrators is quite encouraging.     

Asymmetric and selective object rendering for optimized Cloud Mobile 3D Display Gaming user experience

Cloud Mobile 3D Display Gaming has been recently proposed where 3D video rendering and encoding are performed on cloud servers, with the resulting 3D video streamed wirelessly to mobile devices with 3D displays. This approach has the advantage of relieving high computation, power and storage requirements of 3D display gaming from mobile devices, while enabling game developers to focus on a single rich version of the game which can be experienced from any mobile device and platform. However, it is challenging to stream 3D video over dynamically fluctuating and often constrained mobile networks. In this paper, we propose a novel technique called Asymmetric and Selective Object Rendering (ASOR) which proves to be more powerful than previous solutions for Cloud based Mobile 3D display gaming. Specifically, this technique will enable rendering engine to intelligently decide whether or not to render an individual object and how good the corresponding texture detail will be if rendered, and the settings can be asymmetric for two views. Thus, unimportant objects can trade quality for reduced bitrate while important objects can remain high quality so that the overall user experience is optimized given certain bandwidth constraints. To quantitatively measure the user experience and bitrate by applying different rendering settings, we develop a user experience model and a bitrate model. We further propose an optimization algorithm which uses the above two models to automatically decide the optimal rendering settings for left view and right view to ensure the best user experience given the network conditions. Experiments conducted using real 4G-LTE network profiles on commercial cloud service with different genres of games demonstrate significant improvement in user experience when the proposed optimization algorithm is applied.     

Ray-driven dynamic working set rendering

Ray tracing a volume scene graph composed of multiple point-based volume objects (PBVO) can produce high quality images with effects such as shadows and constructive operations. A naive approach, however, would demand an overwhelming amount of memory to accommodate all point datasets and their associated control structures such as octrees. This paper describes an out-of-core approach for rendering such a scene graph in a scalable manner. In order to address the difficulty in pre-determining the order of data caching, we introduce a technique based on a dynamic, in-core working set. We present a ray-driven algorithm for predicting the working set automatically. This allows both the data and the control structures required for ray tracing to be dynamically pre-fetched according to access patterns determined based on captured knowledge of ray-data intersection. We have conducted a series of experiments on the scalability of the technique using working sets and datasets of different sizes. With the aid of both qualitative and quantitative analysis, we demonstrate that this approach allows the rendering of multiple large PBVOs in a volume scene graph to be performed on desktop computers.     

Nonphotorealistic Rendering by Q-mapping

We present Q-mapping which is a technique for rendering three-dimensional objects using nonphotorealistic cues, by applying Q-maps. Q-maps are three-dimensional textures that make marks on objects, and thus provide visual cues for shape, shade, and texture. Q-maps adapt to light intensity, typically by making more marks in darker areas. Q-maps can produce images with a very wide range of visual styles (e.g. half tone shading, and pen-and-ink colour wash). The primary contribution is that these styles reside in a single parametric space. Importantly this space includes photorealism as a style, which is therefore regarded as a special case of nonphotorealistic image rendering in general. We illustrate our explanation of Q-mapping using examples from scientific visualisation and computer graphics – and provide a gallery of images to show the versatility of the approach.     

点模型及其绘制技术研究

点模型是一种新的三维模型表示方法。同传统的三角网格模型相比,点模型适合处理外形非常复杂并且不规则的几何体。对于这样的几何体,它既能实现高效率的交互式绘制,也能实现高质量的反走样绘制。讨论了点模型的概念,介绍了点绘制的基本思路与基本步骤,以及点绘制中的加速技术,同时展望了未来的研究方向。     

高质量图像绘制的LDI改进算法

对于漫反射场景,LayeredDepthImage(LDI)能够产生很好的绘制效果,但对于高光的场景,它存在绘制图像失真的问题。文章提出一种能够有效地绘制漫反射和高光场景的LDI改进算法。该算法对LDI的每个深度像素增加一个方向向量,对位于同一深度的像素采用加权平均的方法生成新视点下的目标图像。同时采用将方向向量离散化的方法,有效地降低了存储量。实验表明,新算法在绘制速度和绘制质量方面都取得了比较理想的效果。     

GPU Rendering of Relief Mapped Conical Frusta

This paper proposes to use relief‐mapped conical frusta (cones cut by planes) to skin skeletal objects. Based on this representation, current programmable graphics hardware can perform the rendering with only minimal communication between the CPU and GPU. A consistent definition of conical frusta including texture parametrization and a continuous surface normal is provided. Rendering is performed by analytical ray casting of the relief‐mapped frusta directly on the GPU. We demonstrate both static and animated objects rendered using our technique and compare to polygonal renderings of similar quality.     

基于标准PC机的大数据实时体绘制算法研究究

为了解决在标准PC机上对大数据进行实时体绘制的问题，提出了一种基于图形处理器的大数据高质量体绘制算法。该算法采用三维纹理映射作为核心的绘制算法，结合可见性测试、遮挡测试和模板测试来加快绘制速度。实验结果表明，对虚拟人体数据，可以在不损失图像质量的前提下，以可交互的速度进行绘制。     

Choosing rendering parameters for effective communication of 3Dshape

We conducted a series of perceptual experiments to assess the contributions of rendering parameters to the perception of the shape of three-dimensional objects. For the experiments, observers viewed graphically rendered displays consisting of pairs of rotating objects and judged whether their shapes were identical. For some pairs they were, while for other pairs they differed by varying amounts. We determined the accuracy of shape perception from these discrimination judgments. We provide background information for the operational definition of shape used throughout the experiments, as well as for the rendering factors under experimental investigation: occluding contour, smooth shading, and specular highlights. Following that, we describe a series of experiments. Experiment 1 demonstrated the effectiveness of our new technique for the exploration of perceptual issues related to graphic interfaces. An additional four experiments produced results concerning the effects of rendering parameters on the communication of 3D shape. Experiments 2 and 3 investigated the contributions of basic rendering conditions such as the presence of occluding contours and smooth surface shading. In Experiments 4 and 5, the manipulation of specular highlighting revealed that accurate shape discrimination judgments were possible either with or without the specular component. These results lay a foundation for reasoned manipulation of interface properties when accurate communication of 3D shape is a primary goal of the display     

Compressive Volume Rendering

Compressive rendering refers to the process of reconstructing a full image from a small subset of the rendered pixels, thereby expediting the rendering task. In this paper, we empirically investigate three image order techniques for compressive rendering that are suitable for direct volume rendering. The first technique is based on the theory of compressed sensing and leverages the sparsity of the image gradient in the Fourier domain. The latter techniques exploit smoothness properties of the rendered image; the second technique recovers the missing pixels via a total variation minimization procedure while the third technique incorporates a smoothness prior in a variational reconstruction framework employing interpolating cubic B‐splines. We compare and contrast the three techniques in terms of quality, efficiency and sensitivity to the distribution of pixels. Our results show that smoothness‐based techniques significantly outperform techniques that are based on compressed sensing and are also robust in the presence of highly incomplete information. We achieve high quality recovery with as little as 20% of the pixels distributed uniformly in screen space.     

Integrating Occlusion Culling and Levels of Detail through Hardly-Visible Sets

Occlusion culling and level-of-detail rendering have become two powerful tools for accelerating the handling of very large models in real-time visualization applications. We present a framework that combines both techniques to improve rendering times. Classical occlusion culling algorithms compute potentially visible sets (PVS), which are supersets of the sets of visible polygons. The novelty of our approach is to estimate the degree of visibility of each object of the PVS using synthesized coarse occluders. This allows to arrange the objects of each PVS into several Hardly-Visible Sets (HVS) with similar occlusion degree. According to image accuracy and frame rate requirements, HVS provide a way to avoid sending to the graphics pipeline those objects whose pixel contribution is low due to partial occlusion. The image error can be bounded by the user at navigation time. On the other hand, as HVS offer a tighter estimation of the pixel contribution for each scene object, it can be used for a more convenient selection of the level-of-detail at which objects are rendered. In this paper, we describe the new framework technique, provide details of its implementation using a visibility octree as the chosen occlusion culling data structure and show some experimental results on the image quality.     

基于贪心策略的多结点并行光线跟踪负载均衡算法

为了提高利用光线跟踪集群绘制生成高分辨率复杂场景画面的并行度,提出基于 贪心策略的多结点并行光线跟踪负载均衡算法。首先根据 GPU 的并行特性将屏幕空间划分成若 干正方形图像块,并基于移动物体球形包围体在屏幕空间的投影构建二值绘制时间影响度图。 然后依据时空相关性利用上一帧图像块耗时和二值绘制时间影响度图建立渲染任务队列,通过 两步负载均衡实现多渲染结点任务的动态分配。最后进行了实验验证和分析,结果表明该方法 具有良好的负载均衡效果,在 5 个渲染结点的绘制效率最高能提升 4.96 倍。     

Progressive volume rendering of large unstructured grids

We describe a new progressive technique that allows real-time rendering of extremely large tetrahedral meshes. Our approach uses a client-server architecture to incrementally stream portions of the mesh from a server to a client which refines the quality of the approximate rendering until it converges to a full quality rendering. The results of previous steps are re-used in each subsequent refinement, thus leading to an efficient rendering. Our novel approach keeps very little geometry on the client and works by refining a set of rendered images at each step. Our interactive representation of the dataset is efficient, light-weight, and high quality. We present a framework for the exploration of large datasets stored on a remote server with a thin client that is capable of rendering and managing full quality volume visualizations.     

Motion Blur for EWA Surface Splatting

This paper presents a novel framework for elliptical weighted average (EWA) surface splatting with time‐varying scenes. We extend the theoretical basis of the original framework by replacing the 2D surface reconstruction filters by 3D kernels which unify the spatial and temporal component of moving objects. Based on the newly derived mathematical framework we introduce a rendering algorithm that supports the generation of high‐quality motion blur for point‐based objects using a piecewise linear approximation of the motion. The rendering algorithm applies ellipsoids as rendering primitives which are constructed by extending planar EWA surface splats into the temporal dimension along the instantaneous motion vector. Finally, we present an implementation of the proposed rendering algorithm with approximated occlusion handling using advanced features of modern GPUs and show its capability of producing motion‐blurred result images at interactive frame rates.