Shang-Ching Chou

Conflicts classification and solving for collaborative feature modeling

Based on the analysis of feature modeling activities in a collaborative environment, a definition and a classification of concurrency conflicts have been presented. A feature adjustment method is proposed to solve the conflicts, an enhanced naming mechanism for the collaborative feature modeling to preserve the design intentions, and a process for the non-locked multi-client collaborative design. The algorithms have been implemented in a prototype system integrating C++, Java3D and VRML, and CORBA technologies. Flexibility and efficiency in collaborative feature modeling environment have been achieved in our system.

Collaborative virtual environment for feature based modeling

CVE makes collaborative feature modeling among multi-users possible, but the token-passing method that most of current collaborative feature modeling systems use as its collaborative strategy makes the design inflexible and inefficient. Based on the analysis of feature operation in collaborative environment, we propose a new method to solve the conflicts and define a process for non-locked multi-user collaborative design. Based on this method, we have implemented a prototype system integrating C++, Java3D and VML, CORBA technologies to achieve flexibility and efficiency in CVE for feature based modeling.

Real-Time rain simulation

An efficient method for rain simulation in 3D environment is proposed in this paper. By taking advantage of the parallelism and programmability of GPUs (Graphic Processing Units), real-time interaction can be achieved. Splashing of raindrop is simulated using collision detection, series of stylized textures and rotations of point sprites. To simulate wind-driven raining effect, the motion of particles can be freely controlled based on Newtonian dynamics. We can also control the size of raindrops dynamically by using different textures or changing the size of point sprites. To achieve living rendering of raining scenes, the effects have been applied such as lighting, DOF (depth of field). Many experiments have been done in 3D scenes with different geometries complexity and particle system complexity. The test results show that our method is efficient and is feasible to solve the problem of real-time rain simulation for 3D scenes with complex geometries.

Real-time rain simulation in cartoon style

An efficient method for simulating cartoon style rain in 3D environment is proposed here. By taking advantage of the parallelism and programmability of GPUs (graphic processing units), real-time interaction can be achieved. Splashing of raindrop is simulated using collision detection, series of stylized textures and rotations of point sprites. To simulate wind-driven raining effect, the motion of particles can be freely controlled based on Newtonian dynamics. We can also control the size of raindrops dynamically by using different textures or changing the size of point sprites. Many experiments have been done in 3D scenes with different complexity and GPU-based stylized rendering. The experimental results demonstrated the efficiency of our method for real-time rain simulation in cartoon style with complex geometries of 3D scenes.

Real-time rendering of raining animation based on the graphics hardware acceleration

We present an efficient method for simulation of raining phenomenon in real time by taking advantage of the parallelism and programmability of GPU (graphic processing unit). Our implementation of the method is based on particle systems and collision detection. Splashing of raindrop is simulated using a series of stylized textures and rotations of point sprites. Taking into account human perception in raining phenomenon of real world, the effects such as light influence, depth of field, motion blur, have been applied. The test results show that our method is efficient and is feasible to solve the problem of 3D raining simulation in real time for more general environment with complex geometry.

Real-Time shadow volume algorithm for subdivision surface based models

This paper presents a purely hardware-accelerated shadow volume algorithm for subdivision surface based models. By introducing SP (subdivision patterns), all procedures, including subdivision evaluation, silhouette extraction, shadow volume generation, and shadow rendering are executed on GPU (Graphics Process Units) efficiently. This not only alleviates the burden of CPU, but also guarantees the consistency of data among different processing stages. This also makes it possible to integrate some special effects imposed by other shaders, e.g., displacement mapping or vertex texturing, with the shadow volume algorithm. Experiments show that the algorithm is efficient, robust, and can be easily extended to other subdivision schemes and parametric surfaces.

Model compression and transmission in collaborative CAD

CAD systems increasingly require distributed collaborative design capabilities to meet the designers at different geographical locations to co-develop parts. It involves transmitting the CAD models back and forth among the systems in a distributed design environment. However, it is very difficult to apply because the CAD models are always very complex and the current network bandwidth is limited. In this paper, some important work about the compression and transmission of CAD models through the network is elaborated. Meanwhile, because a feature-based model always contains many extruded and revolved features, then we propose a new approach to transmission of feature-based models to deal with these extruded and revolved features. This approach can effectively cut down the transmission delay of the feature-based models, especially when the model contains many extruded and revolved features.

GridCAD: A Collaborative CAD System Based on Grid Computing

AbstractCurrent works on distributive and collaborative CAD systems often focus on collaborative request submitting, but not distributively executing. A new approach to integrating Grid Computing into Collaborative CAD system is proposed in this paper. A prototype system GridCAD based on this approach is implemented with Web Services based Grid Computing technology. XML/SOAP is adopted as the communications mechanism between Server and Clients. The Session Manager provides the solution of validity maintenance of product models under collaborative environments. In particular, as the core module, Task Manager enables GridCAD to dynamically split complex operations and to distributively perform subtasks. GridCAD also guarantees interoperability on heterogeneous systems so that different types of systems can communicate smoothly and perform the computation much faster than on a single machine.

Concurrency conflicts solving for collaborative feature modeling

Most of current collaborative feature modeling systems use the token-passing method as its collaborative strategy that makes the collaborative design between multi-clients inflexible and inefficient. Based on the analysis of feature operation in collaborative environment, we propose a new method to solve the concurrency conflicts, an enhanced naming mechanism for collaborative feature modeling to preserve the design intensions, and a process for non-locked multi-client collaborative design. The algorithms have been implemented in a prototype system integrating C++, Java3D and VML, CORBA technologies. Flexibility and efficiency in collaborative feature modeling environment have been achieved in our system.

Intersect offsets of parametric surfaces with branch analysis

Based on the methods for solving contouring problem, we present an algorithm to compute the intersection of offsets of parametric surfaces robustly, accurately and efficiently. By first determining the topology of intersection, the algorithm makes tracing process smoothly. Resulting intersection curves is given inform of the trajectory of the parametric domains of the original surfaces, no approximation of offset surface is needed. The algorithm also does not need to inverse the 3D intersection to 2D parametric domains. The intersection is defined by a single parameter in interval [0,1]. The algorithm have been implemented and tested. It can overcome the degenerate conditions such as loop leaking, branch jumping, and disorder tracing, and it can also calculate the intersection robustly and accurately.