Feature-Adaptive Rendering of Loop Subdivision Surfaces on Modern GPUs

We present a novel approach for real-time rendering Loop subdivision surfaces on modern graphics hardware. Our algorithm evaluates both positions and normals accurately, thus providing the true Loop subdivision surface. The core idea is to recursively refine irregular patches using a GPU compute kernel. All generated regular patches are then directly evaluated and rendered using tile hardware tessellation unit. Our approach handles triangular control meshes of arbitrary topologies and incorporates common subdivision surface features such as semi-sharp creases and hierarchical edits. While surface rendering is accurate up to machine precision, we also enforce a consistent bitwise evaluation of positions and normals at patch boundaries. This is particularly useful in the context of displacement mapping which strictly requires inatching surface normals. Furthermore, we incorporate efficient level-of-detail rendering where subdivision depth and tessellation density can be adjusted on-the-fly. Overall, our algorithm provides high-quality results at real-time frame rates, thus being ideally suited to interactive rendering applications such as video games or authoring tools.     

A meshing scheme for efficient hardware implementation of butterfly subdivision using displacement mapping

Displacement mapping is an effective technique for encoding the high levels of detail of surface models using coarse triangle meshes and displacement maps. These maps are 2D representations containing the distances between the coarse mesh and the surface to represent. Displacement maps have been used in many applications such as ray tracing, image warping, and volume rendering. In this article, we propose modifications to our previous grouping strategy, a new subdivision strategy based on the Modified Butterfly algorithm and new heuristics for the adaptive subdivision procedure, and, finally, the corresponding modifications on our hardware proposal. A meshing scheme and an adaptive subdivision strategy based on displacement mapping reduce the bottleneck between the CPU and graphics pipeline common in high-performance graphics systems.     

An interactive FORTRAN 77 program using GKS graphics for 2.5 D modeling of gravity and magnetic data

An interactive 2.5 D gravity and magnetics modeling program has been written for an ICL PERQ 2 workstation using FORTRAN 77 and GKS graphics. All of the available hardware and software input devices are utilized through GKS to produce an easy-to-use menu-driven program. A large number of functions are controlled by the software in order than the user can concentrate on the model. A range of options also are provided for manipulating the observed anomaly. The use of FORTRAN 77 and GKS should make the program easily portable to other computer systems and graphics devices. The modular form of the program should facilitate readily further development including optimization and real time modeling, given a more powerful computer with high-speed graphics.     

Efficient skeleton-guided displaced subdivision surfaces

Displacement mapping is a computer graphics technique that uses scalar offsets along normals on a base surface to represent and render a model with highly geometric details. The technique natively compresses the model and saves memory I/O. A subdivision surface is the ideal base surface, due to its good geometric properties, such as arbitrary topology, global smoothness, and multi-resolution via hardware tessellation, among others. Two of the main challenges in displacement mapping representation are constructing the base surface faithfully and generating displacement maps efficiently. In this paper, we propose an efficient skeleton-guided displaced subdivision surfaces method. The construction of the base mesh is guided by a sketched skeleton. To make the shape of the base surface fit the input model well, we develop an efficient progressive GPU-based subdivision fitting method. Finally, a GPU-based raycasting method is proposed to sample the input model and generate the displacement maps. The experimental results demonstrate that the proposed method can efficiently generate a high-quality displacement mapping representation. Compared with the traditional displaced subdivision surface method, the proposed method is more suitable for the modern rendering pipeline and has higher efficiency.     

Dynamic Catmull-Clark subdivision surfaces

Recursive subdivision schemes have been extensively used in computer graphics, computer-aided geometric design, and scientific visualization for modeling smooth surfaces of arbitrary topology. Recursive subdivision generates a visually pleasing smooth surface in the limit from an initial user-specified polygonal mesh through the repeated application of a fixed set of subdivision rules. We present a new dynamic surface model based on the Catmull-Clark subdivision scheme, a popular technique for modeling complicated objects of arbitrary genus. Our new dynamic surface model inherits the attractive properties of the Catmull-Clark subdivision scheme, as well as those of the physics-based models. This new model provides a direct and intuitive means of manipulating geometric shapes, and an efficient hierarchical approach for recovering complex shapes from large range and volume data sets using very few degrees of freedom (control vertices). We provide an analytic formulation and introduce the “physical” quantities required to develop the dynamic subdivision surface model which can be interactively deformed by applying synthesized forces. The governing dynamic differential equation is derived using Lagrangian mechanics and the finite element method. Our experiments demonstrate that this new dynamic model has a promising future in computer graphics, geometric shape design, and scientific visualization     

插值Doo-Sabin表面形状调节

修改了插值的Doo-Sabin细分表面的初始控制网格，在第一次细分的同时加入了表面调节参数。这个方案具有以下特征：1）满足插值所有顶点或某些顶点的同时可以由参数调节极限表面；增加了对极限表面的调节自由度。2）整个的计算复杂度为O(k),其中k是顶点的数量。在最后也对结果表面的形状处理进行了讨论。     

Displaced subdivision surfaces of animated meshes

This paper proposes a novel technique for converting a given animated mesh into a series of displaced subdivision surfaces. Instead of independently converting each mesh frame in the animated mesh, our technique produces displaced subdivision surfaces that share the same topology of the control mesh and a single displacement map. We first propose a conversion framework that enables sharing the same control mesh topology and a single displacement map among frames, and then present the details of the components in the framework. Each component is specifically designed to minimize the shape conversion errors that can be caused by enforcing a single displacement map. The resulting displaced subdivision surfaces have a compact representation, while reproducing the details of the original animated mesh. The representation can also be used for efficient rendering on modern graphics hardware that supports accelerated rendering of subdivision surfaces.     

Cords: geometric curve primitives for modeling contact

Curves are perhaps the most versatile of modeling primitives in computer graphics. They define a rough structure for many surface-generation algorithms and are often fit to meaningful surface features for further shape modeling. Deformable objects such as hair and fur are simulated on finite element curve discretizations. Motion paths for planning and animation applications are tied to underlying curves. In this article we present a geometric curve primitive, known as a cord, which allows for interactive modeling of curves that contact complex geometry.     

浅析3D动漫造型协同创新设计方法

动漫造型的设计是一项依赖于脑力、创造力以及想象力的活动,能够体现出知识经济的特点,其中需要交互式的图形系统和分析计算为主的计算机辅助设计系统,这样才能为设计人员提供工具,实现人机交互．但是这并不能为设计人员的创造性思维有所帮助,也不能支持协同设计。本文首先对3D动漫造型的发展情况进行简述,之后分析3D动漫造型协同创新设计研究现状,结合现状提出3D动漫造型协同创新设计方法,从而引发动漫产业在国际市场上的发展,保证期发展前景的广阔性。     

Displacement patches for view-dependent rendering

In this paper we present a new approach for interactive view-dependent rendering of large polygonal data sets which relies on advanced features of modern graphics hardware. Our preprocessing algorithm starts by generating a simplified representation of the input mesh. It then builds a multiresolution hierarchy for the simplified model. For each face in the hierarchy, it generates and assigns a displacement map that resembles the original surface represented by that face. At runtime, the multiresolution hierarchy is used to select a coarse view-dependent level-of-detail representation, which is sent to the graphics hardware. The GPU then refines the coarse representation by replacing each face with a planar tile, which is elevated according to the assigned displacement map. Our results show that our implementation achieves quality images at high frame rates.     

A simple method for interpolating meshes of arbitrary topology by Catmull–Clark surfaces

Interpolating an arbitrary topology mesh by a smooth surface plays important role in geometric modeling and computer graphics. In this paper we present an efficient new algorithm for constructing Catmull–Clark surface that interpolates a given mesh. The control mesh of the interpolating surface is obtained by one Catmull–Clark subdivision of the given mesh with modified geometric rule. Two methods—push-back operation based method and normal-based method—are presented for the new geometric rule. The interpolation method has the following features: (1) Efficiency: we obtain a generalized cubic B-spline surface to interpolate any given mesh in a robust and simple manner. (2) Simplicity: we use only simple geometric rule to construct control mesh for the interpolating subdivision surface. (3) Locality: the perturbation of a given vertex only influences the surface shape near this vertex. (4) Freedom: for each edge and face, there is one degree of freedom to adjust the shape of the limit surface. These features make interpolation using Catmull–Clark surfaces very simple and thus make the method itself suitable for interactive free-form shape design.     

GPU-based real-time acoustical occlusion modeling

In typical environments, the direct path between a sound source and a listener is often occluded. However, due to the phenomenon of diffraction, sound still reaches the listener by “bending” around an obstacle that lies directly in the line of straight propagation. Modeling occlusion/diffraction effects is a difficult and computationally intensive task and thus generally ignored in virtual reality and videogame applications. Driven by the gaming industry, consumer computer graphics hardware and the graphics processing unit (GPU) in particular, have greatly advanced in recent years, outperforming the computational capacity of central processing units. Given the affordability, widespread use, and availability of computer graphics hardware, here we describe a computationally efficient GPU-based method that approximates acoustical occlusion/diffraction effects in real time. Although the method has been developed primarily for videogames where occlusion/diffraction is typically overlooked, it is relevant for dynamic and interactive virtual environments as well.     

Hardware/software trade-offs for bitmap graphics on the blit

The Blit is an experimental bitmap graphics terminal built for research into interactive computer graphics on the UNIX time-sharing system. The hardware is inexpensive and the graphics functions are implemented entirely in software. Nevertheless, the graphics performance of the Blit is comparable or superior to some displays with special-purpose graphics hardware. This paper explains the paradox by referring to some principles of design: the hardware and software should be designed together to complement each other; carefully designed software can outperform infelicitous hardware; and simplicity of design leads to efficiency of execution. These principles are illustrated by examples from the Blit hardware and software and comparisons with other systems.     

基于GPU的视点相关自适应细分

利用GPU的强大浮点数计算能力和并行处理能力,提出一种完全基于GPU的视点相关自适应细分内核进行快速细分计算的方法.在GPU中,依次实现视点相关的面片细分深度值计算、基于基函数表的细分表面顶点求值、细分表面绘制等核心步骤,无须与CPU端系统内存进行几何数据交换.视点相关的自适应细分准则在表面绘制精度保持不变的情况下,有效地降低了细分表面的细分深度和细分的计算量,在此基础上完全基于GPU的细分框架使得曲面细分具有快速高效的特点.该方法还可以在局部重要细节用较大深度值进行实时自适应细分,以逼近极限曲面.     

Solid modeling of polyhedral objects by Layered Depth-Normal Images on the GPU

We introduce a novel solid modeling framework taking advantage of the architecture of parallel computing on modern graphics hardware. Solid models in this framework are represented by an extension of the ray representation — Layered Depth-Normal Images (LDNI), which inherits the good properties of Boolean simplicity, localization and domain decoupling. The defect of ray representation in computational intensity has been overcome by the newly developed parallel algorithms running on the graphics hardware equipped with Graphics Processing Unit (GPU). The LDNI for a solid model whose boundary is represented by a closed polygonal mesh can be generated efficiently with the help of hardware accelerated sampling. The parallel algorithm for computing Boolean operations on two LDNI solids runs well on modern graphics hardware. A parallel algorithm is also introduced in this paper to convert LDNI solids to sharp-feature preserved polygonal mesh surfaces, which can be used in downstream applications (e.g., finite element analysis). Different from those GPU-based techniques for rendering CSG-tree of solid models Hable and Rossignac (2007, 2005) [1] and [2], we compute and store the shape of objects in solid modeling completely on graphics hardware. This greatly eliminates the communication bottleneck between the graphics memory and the main memory.     

基于曲率流的四边形主导网格的光顺方法

网格模型是计算机图形学和数字几何处理中运用最为广泛的三维几何表达方式.四边网格(以四边形为主的网格)由于其符合人们对几何形状变化的自然感知,在表示三维几何上有其独有的优势,并且可以更为直接地应用在几何造型、细分曲面、建筑设计等方面.文中针对四边形主导网格含有噪声的情况,设计了一种基于表面微分属性的光顺方法,该方法具有易实现、计算效率高的特点.基于曲率流的几何扩散可以有效地保持原网格的几何特征,同时还针对四边形主导网格的T-顶点进行了特殊处理.     

基于区域特征距离加权的三维地形建模方法

为了提高三维虚拟场景中三维地形真实感效果,提出了基于区域特征的距离加权的三维地形建模方法。首先,根据采样点数据的高程值对采样点数据进行分类,建立分类数据与插值点数量映射关系;然后,结合Diamond-square细分法求取插值点坐标数据,求得距离加权因子;最后,通过判断插值点的区域特征建立距离加权计算方程,以保证插值点间的平滑性和连贯性。理论分析和仿真结果表明,与传统地形建模方法相比,该方法能够提高三维地形的真实感,同时地形绘制速度提高20%。     

Portability of interactive graphics software

One solution to obtaining a portable graphics architecture is presented. By abstracting the functionality present in most 3-D graphics systems and augmenting it with advanced rendering features, a highly portable, efficient, and modern graphics architecture for interactive 3-D graphics applications (including modeling, animation, and scientific visualization) is obtained. Using appropriate object-oriented design procedures ensures the efficiency, maintainability, and portability of the architecture. The design and implementation of the graphics system used to achieve this high degree of portability are described