Presentation on theme: "2009. April. 01 Yongsu Song PNU STEM Lab"— Presentation transcript:
12009. April. 01 Yongsu Song PNU STEM Lab The Quadtree and Related Hierarchical Data Structures HANAN SAMET Computer Science Department, University of Maryland, College Park, Maryland 207422009. April. 01Yongsu SongPNU STEM Lab
2Plan Part 1 : Overview of Quadtree Part 2 : Basic Operation Start, Merge, Split, GroupExample of tilingRope and NetPart 3 : Alternates of QuadtreeOctreeK-d treeApproximation MethodsPart 4 : Conclusion
3Overview of Quadtree Recursive decomposition. Similar to divide and conquerGeographic Information System, Image processing and so on..
4Cont. N H M I O G F B L Q J 37 38 39 40 57 58 59 B F G H I J L M N O Q 1NHMIOGFBLQJ3738394057585960ABCDEFGHIJKLM37383940NOPQ57586059
6Example of tiling Uniform orientation Easy to implement Yamaguchi et al. Triangular quadtree to generate anisometric view from octree. (3D)
7Rope and Net Fast! But.. N H M I O G F B L Q J 3738394057585960Rope : Link between two adjacentnodes of equal size where atleast one of them is a leaf node.Net : Linked list whose elements are all the nodesthat are adjacent along a given side of a node.ABCDEFGHIJKLM37383940NOPQ57586059Fast!But..
8Alternates of Quadtree k-d tree Fewer leaf nodes : 4 sons -> 2 sonsGood at higher dimensional data!
9Point quadtree vs k-d tree 2^k branching factor for k dimensionk-d tree
10Approximation Methods Image approximation.Shape approximation.Good : High resolution levels to low resolution.Bad : Comparing similar shapes.
11OctreeStructure to store the volume elementIs it possible?
13Curvilinear Data Boundaries of regions? Strip tree More complex? Point to left child node?Point to right child nodeX1Y1X2Y2WLWR
14Cont. Special case Closed curve by strip tree. Extends past its endpoints.So what?
15Cont. Intersecting two strip trees. Curve approximation. Null Clear. Possible
16Conclusion The main idea Efficient For Region and Point Recursive decompositionEfficient For Region and PointDivide and conquerReduce size range of target dataImportant of data structureApply Approximation skills