Zhao Qinping

Adaptive mechanisms of organizational structures in multi-agent systems

Organizational adaptation is one of the key issues of organization and reorganization theories. As the result of environmental changes, organizations can change their internal structures or agents in the organizations can adjust their behaviors to achieve organizational objectives. In this paper, we focus on the characteristics of organizational structures and also analyze the notion of organizational stability and its changes resulted from the constraints of roles and their relations in the organizational structure. In the end, we give a formal specification of the adaptive mechanisms for organizational structures in details to meet dynamic environment requirements.

Organ Texture Synthesis for Virtual Reality-Based Surgical Simulators

Virtual Reality-based simulators is an important tool for surgical skills training and assessment. In general, the degree of realism experienced by the trainees is determined by the visual and biomechanical fidelity of the simulator. Organ textures can greatly affect visual realism and hence the overall quality of the simulation. In this paper, we use a very simple algorithm that can efficiently synthesize a wide variety of organ textures. The algorithm uses pixel-based texture synthesize technology. For each pixel in the output image, an L-shaped neighborhood of current pixel of a specific size is considered. Each pixel from this neighborhood generates a “shifted” candidate pixel according to its original position in the input texture. The best pixel is chosen with a neighborhood most similar to the current L-shaped neighborhood in the output image. This method is fast and its implementation is straightforward. The experiment results show the algorithm is feasility and validity.

Bleeding Simulation Based Particle System for Surgical Simulator

Bleeding simulation is important components of a surgical simulator. However, realistic simulation of bleeding is a challenging problem. There are several fluid flow models described in the literature, but they are computationally slow and do not satisfy real-time requirement of a surgical simulator. The paper introduce a bleeding simulation algorithm based on the particle system and implement arterial squirting blood, blood splashes in free space, blood drops running down a surface. This algorithm calculates how many blood particles are needed to model a particular instance of bleeding, and assigns a velocity to each particle in a gravitational field so that particles flow out of the injured region at the proper rate. The key characteristics of our algorithm are a visually realistic display and real-time computational performance. Experiment results show that proposed method is feasible and effective. In addition, this algorithm can also be used to simulate water irrigation and smoke effect in virtual surgery simulator.

Compact Compression for 3D Dynamic Datasets in Certain Range

In remote visualization for complex 3D dynamic datasets, existing vertex compression algorithms have low compression factor, and compressed datasets cannot be transmitted to client in once if its size is bigger than bandwidth. In order to solve these problems, this paper presents a compact impression for 3D dynamic datasets in certain range. We construct an equilateral triangle to obtain and compress parts of original datasets, which realizes rigid body decomposition in certain range. In order to promote compression factor, we also introduce a temporal rigid body decomposition to group vertices with temporal trajectory consistency. The results of the experiments show that our algorithm can obtain high compression factor for dynamic datasets in certain range to reduce limitation of bandwidth.

Shadow rendering for mesostructure surface based on height gradient map

The objects with mesostructure surfaces have difficulty in geometric modeling and have complex model structures, which result in low efficiency of shadow rendering algorithms. This paper presents a real-time rendering method for soft shadow based on height gradient map. To realize the real-time rendering, we propose a mesostructure description model, which has the mesostructure height field tied to the surfaces of low-resolution models by using texture coordinates to exhibit complex mesostructure models. We also introduce mesostructure height gradient map (MHGM) to create local apex sets of visible points. In the shadow rendering stage, the detailed shadow is generated by computing the occlusion of gradient-space local apex sets in real time. Our algorithm runs entirely in image space, and uses deferred shading and the graphics pipeline to show the self-shadowing effect of deformable objects in dynamic scenes.

Apply two pass aggregation to real-time stereo matching

The stereo-matching algorithm based on adaptive-weight can produce disparity map of high precision. However it is not suitable for real-time application due to high computational complexity. Wang etc apply one pass aggregation to adaptive-weight algorithm and can achieve real-time performance but with a much lower precision. This paper presents a new real-time adaptive weight stereo matching algorithm based on two-pass aggregation: Matching costs are aggregated by row and array in order to reduce the computational complexity, some measures are taken to reduce the accuracy lost; then a fast dynamic programming combined greedy strategy and disparity smoothness constraint is adopted to select disparity. Evaluation results in MiddleBury platform show that the algorithm ranked No.2 among all real-time algorithms in this platform and the average error rate is the smallest. Also this algorithm achieves a good real-time performance.

Ambient occlusion in screen-space for mesostructure objects

In the traditional ambient occlusion algorithm for microstructures, the determination of occlusion is a time-consuming task. To improve the rendering speed, the paper proposes a screen-based ambient occlusion method. By using off-screen technique, only the visible points are used to determine the occlusion. Using the depth texture of the whole scene, the size of ambient occlusion can be quickly computed by the maximum of the block angle. The whole scene can be rendered using the deferred shading technology. Experimental results show that our method is more efficient than the available methods on computing the ambient occlusion. It does not need any pre-processing, and the time used for ambient occlusion determination is less than other methods.

Keep region for constructing LOD of terrain regular mesh

We present an improved ROAM algorithm for keeping region when rendering terrain. Concerning the region broken problem of ROAM algorithm in rendering terrain, a method of keeping region in rendering terrain with enhancing the triangle splitting condition is proposed. The concept of optimum triangulation for region is used to set the splitting vertex and its parent active. The rending algorithm sets status of the active vertex according to the view direction and the distance between viewpoint and region, and produces the terrain region s level of detail. The results of experiments show that our algorithm with LOD has a satisfactory performance in keeping region during rending terrain