Yanning Xu

A system framework and key techniques for multi-user cooperative interaction in virtual museum based on Voronoi diagram

This paper describes a system framework of 3D virtual museum supporting multi-user cooperative interaction. To a 3D virtual museum, the building (empty scene) can be projected to a 2D polygon. Hence, we can manage the data of collections and users based on the scene polygons Voronoi diagram. We can get the Voronoi diagram by subdividing the polygon into some cells using the proximity characteristic. We also establish some communication rules between users. In this article, how to compute visibility and detect collisions based on polygons Voronoi diagram is discussed and this method is aimed to improve the reality and coherence of cooperative interaction in virtual museum.

A semantic Web based model for product cooperative design

A semantic Web based model for product cooperative design is proposed by enabling engineering knowledge to be published, discovered, reused, and integrated. Three features of the model are described in detail. The first is the tools for Web design, which enable a design process to be published as a service and then to be reused as a design resource in other design processes; the second is the ontology of design resources, which helps the implementation of intelligent retrieval by semantic inference; the third is design workflows, which enable designers to construct complex design with the existing simple design instances.

Coherent Photon Mapping on the Intel MIC Architecture

Photon mapping is a global illumination algorithm which is composed of two steps: photon tracing and photon searching. During photon searching step, each shading point needs to search the photon-tree to find k-neighbouring photons for reflected radiance estimation. As the number of shading points and the size of photon-tree are dramatically large, the photon searching step is time consuming. We propose a parallel photon searching algorithm by using radiance estimation approach for coherent shading points on the Intel® Many Integrated Core (MIC) Architecture. In order to efficiently use single instruction multiple data (SIMD) units, shading points are clustered by similarity first (every cluster contains 16 shading-points), and an initial neighbouring scope is searched from the photon-tree for each cluster. Then we use 16-wide SIMD units by performing k-NN searching from the initial neighbouring scope for those 16 shading-points in a cluster in parallel. We use the method to simulate some global illumination scenes on Intel® Xeon® processors and Intel® Xeon® Phi™ coprocessors. The comparison results with existing photon mapping techniques indicate that our method gives significant improvement in speed with the same accuracy.

Fast Point Based Global Illumination

Point based rendering can simulate global illumination phenomenon fast and is widely used in movie production. This paper proposes a faster point based global illumination algorithm compared with the standard one. During our algorithm, the shading points generated by ray tracing are clustered in to groups. When doing point based rendering, the indirect illumination of each groups center point is computed instead of each shading point. We use an error strategy to make the indirect illumination compute adaptively. This method is several times faster than the standard point based global illumination method, while preserves high rendering quality. Whats more, we implement our algorithm on GPU. In order to improve parallelism, we design a GPU-based cluster method and then implement the point based rendering process on GPU. The speed is times faster compared with the CPU one.

Real-Time Collaborative Design System for Product Assembly Over the Internet

Product assembly design is a complex activity possible involving collaboration between different designers geographically dispersed. This paper puts forward some significant methodologies and technologies for distributed assembly and presents a collaboration architecture that manages to support working in both synchronous and asynchronous ways. Meanwhile, we adopt a three-level conflicts detection scheme to avoid conflicts effectively and a data streaming technology based on C/P (command/parameter) to realize the real-time design. Based on the technologies mentioned above, a design system that supports real-time collaborative assembly is developed and we validate it by assembling a mechanical press across network collaboratively.

Cooperative design and data management of virtual museum based on Voronoi diagram

This paper mainly discusses how to design a virtual museum system used by many users at the same time, and how to manage the scene data. To a 3D indoor scene, the empty scene (only the building) without other objects such as collections can be created by sweeping a 2D polygon along an axis which is perpendicular to the horizontal plane. We can create the scene polygons Voronoi diagram, which subdivides the polygon into some cells called Voronoi regions by the proximity characteristic. An edge of the polygon corresponding to a wall of the building has its own Voronoi region where all the points are nearest to the edge than others. Hence, every user can select one Voronoi region to lay out collections such as cultural relics on the exhibition platform and every collection is saved by the Voronoi region in which it is laid out. Based on the scene polygons Voronoi diagram, the system can also support multi-user cooperative interaction in the created scene very well. The work also can be used to create virtual art gallery, product exhibition hall and so on.

Vectorized point based global illumination on Intel MIC architecture

Abstract Point-based global illumination (PBGI) is a popular rendering method in visual special effects and motion picture productions. This rendering algorithm models the 3D scene as a dense point cloud, which acts as caching records for light transport simulation. Structured in a tree, this cache supports the image synthesis stage through massive adaptive tree cut searches, together with the projection of these cuts on the many receiver shading points i.e., unprojected pixels in 3D space, where visibility is solved with receiver-specific z-buffer. These two operations are both time consuming in this algorithm, but they can be formulated for efficient parallel execution, in particular regarding wide-SIMD hardware. During the PBGI tree traversal procedure, we introduce a single-receiver traversal scheme for incoherent receivers, a packet traversal scheme for coherent receivers, as well as logic for dynamically switching between these methods at run-time. During the per-receiver rasterization procedure, we propose three different vectorization strategies for near-, mid- and far-distance points separately. We conducted experiments on an Intel Many Integrated Core (MIC) architecture and report results on several scenes, showing that up to a 9 ×  speedup can be achieved when compared with non-vectorized execution during the traversal step, and nearly 2.5 ×  speedup during rasterization step without quality degradation.

A collaborative design platform for assembly process planning

This paper presents a web-based virtual environment which supports designers geographically distributed to engage in the same assembly scenario and complete the assembly task synchronously. Firstly, a client-server based architecture for collaborative assembly is discussed. The discussion highlights how to decompose the collaborative assembly environment into several functional modules, and how to deploy the right module on the right side. Secondly, some key technologies including task classification and subdivision, and multimodal interaction, are discussed in detail. At last, we give our implementations and discuss limitations in our current research effort.

Progressive photon mapping with sample elimination

Progressive photon mapping [Hachisuka et al. 2008] (PPM) obtains increasingly accurate results with progressive visualization, but it is problematic when results are obtained through thousands of iterations. An uniform photon distribution is critical for the accurate result. In this work, we use the sample elimination [Yuksel 2015] (SE) in PPM to achieve optimal results and accelerate the iterations. Sample elimination can produce sample sets with more pronounced blue noise characteristics. We apply the feature of this elimination method to the progressive iterations.

Adaptive Photon Mapping Based on Gradient

Photon mapping can simulate some special effects efficiently such as shadows and caustics. Photon mapping runs in two phases: the photon map generating phase and the radiance estimation phase. In this paper, we focus on the bandwidth selection process in the second phase, as it can affect the final quality significantly. Poor results with noise arise if few photons are collected, while bias appears if a large number of photons are collected. In order to solve this issue, we propose an adaptive radiance estimation solution to obtain trade-offs between noise and bias by changing the number of neighboring photons and the shape of the collected area according to the radiance gradient. Our approach can be applied in both the direct and the indirect illumination computation. Finally, experimental results show that our approach can produce smoother quality while keeping the high frequency features perfectly compared with the original photon mapping algorithm.