PG2015short
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Browsing PG2015short by Subject "Computational Geometry and Object Modeling"
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Item Accelerating Graph-based Path Planning Through Waypoint Clustering(The Eurographics Association, 2015) Wardhana, Nicholas Mario; Johan, Henry; Seah, Hock-Soon; Stam, Jos and Mitra, Niloy J. and Xu, KunModern Computer Graphics applications commonly feature very large virtual environments and diverse characters which perform different kinds of motions. To accelerate path planning in such scenario, we propose subregion graph data structure. It consists of subregions, which are clusters of locally connected waypoints inside a region, as well as their connectivities. We also present a fast algorithm to automatically generate subregion graph from enhanced waypoint graph map representation, which also supports various motion types and can be created from large virtual environments. Nevertheless, subregion graph can also be generated from any graph-based map representation. Our experiments showed that subregion graph is very compact relative to the input waypoint graph. By firstly planning subregion path, and then limiting waypoint-level planning to the subregion path, up to 8 times average speedup can be achieved, while average length ratios are maintained at as low as 102.5%.Item Incomplete 3D Shape Retrieval via Sparse Dictionary Learning(The Eurographics Association, 2015) Wan, Lili; Jiang, Jingyu; Zhang, Hao; Stam, Jos and Mitra, Niloy J. and Xu, KunHow to deal with missing data is one of the recurring questions in data analysis. The handling of significant missing data is a challenge. In this paper, we are interested in the problem of 3D shape retrieval where the query shape is incomplete with moderate to significant portions of the original shape missing. The key idea of our method is to grasp the basis local descriptors for each shape in the retrieved database by sparse dictionary learning and apply them in sparsely coding the local descriptors of an incomplete query. First, we present a method of computing heat kernel signatures for incomplete shapes. Next, for each shape in the database, a set of basis local descriptors, which is called a dictionary, is learned and taken as its representative. Finally, a query incomplete shape's heat kernel signatures are respectively reconstructed by each dictionary, and the shape similarities are therefore measured by the reconstruction errors. Experimental results show that the proposed method has achieved significant improvements over previous works on retrieving non-rigid incomplete shapes.Item Light-Guided Tree Modeling of Diverse Biomorphs(The Eurographics Association, 2015) Yi, Lei; Li, Hongjun; Guo, Jianwei; Deussen, Oliver; Zhang, Xiaopeng; Stam, Jos and Mitra, Niloy J. and Xu, KunCreation of tree models faithful to light environment is an important task in computer graphics as well as in botanical research, such as horticulture and forestry. In this paper, we propose an approach to model virtual trees with constraints of light resources and tree morphological properties. By the allocation of received light resources, tree model parameters are estimated, including branching directions and branching sizes. The light energy is calculated by sampling the environmental space, so that the final architecture of trees could be modeled corresponding to its growth environments. Experimental results show that the proposed method create trees with architectures guided by light resources.Item Pairwise Surface Registration Using Local Voxelizer(The Eurographics Association, 2015) Song, Peng; Chen, Xiaoping; Stam, Jos and Mitra, Niloy J. and Xu, KunSurface registration is the process that brings scans into a common coordinate system by aligning their overlapping components, which can be achieved by finding a few pairs of matched points on each scan pair using shape descriptors and employing the matches to compute an alignment transformation. This paper proposes a local voxelizer descriptor, and the key idea is to define a unique local reference frame (LRF) using the local shape around a basis point, perform voxlization for the local shape within a cubical volume aligned with the LRF, and concatenate local features extracted from each voxel to construct the descriptor. A pairwise registration algorithm is developed by choosing a single pair of matched points using the local voxelizer descriptor, and computing a rigid transformation based on aligning the corresponding LRFs. Quantitative experiments show that our algorithm can register scan pairs with small overlap, while maintaining acceptable registration accuracy.