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Non-Uniform Terrain Mesh Simplification Using Adaptative Merge Procedures Flávio Luis de Mello Edilberto Strauss Antônio Oliveira Aline Gesualdi

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1. Introduction 2. Mesh Simplification Method 3. Results 4. Conclusion 1

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2 Terrain walkthrough plays an important role in the virtual reality Geographic Information Systems (GIS), Military Mission Planning, Flight Simulation, etc. Regular grid sampled data is required

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3 Relationship between the actual map image resolution and its associated data can easily exceed the capabilities of typical graphics hardware, which makes impossible a real-time interactive application. data fps real-time interaction

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4 Relationship between the actual map image resolution and its associated data can easily exceed the capabilities of typical graphics hardware, which makes impossible a real-time interactive application. data fps real-time interaction At most PII 450MHz No Hw acceleration

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5 Describes an optimized algorithm for building a terrain triangular mesh Combines an efficient regular grid representation with low cost memory requirements Bottom-up approach Based on classic quadtree algorithm (Röttger – Eurograph99)

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Digital Elevation Model (2 n x 2 m ) 6

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7 h=2 2. Terrain Model

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8 Merge Criteria: #1 #2

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2. Terrain Model 9

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Sorted Unsorted 13

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BorderInterior G int =0,9143G border =1,3482 h quadtree 4 to 5 1 st 2 nd 3 rd ProposedRöttgerProposedRöttger 2. Terrain Model 14

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DEM (1.024 x 1.024) h= triangles triangles #=34,34% # R =16,71% h= triangles triangles #=37,57% # R =9,76% h= triangles triangles #=59,375% # R =4,80% 15

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No cracks, no T-junctions Global treatment 16

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No cracks, no T-junctions Global treatment 17

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DEM (2.048 x 2.048) =4,18 m h= triangles triangles #=48,22% # R =16,03% h= triangles triangles #=64,43% # R =8,84% h= triangles triangles #=80,47% # R =4,51% 18

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DEM (1.024 x 1.024) =8,125 m h= triangles triangles #=79,62% # R =12,47% h= triangles triangles #=85,64% # R =7,69% h= triangles triangles #=91,30% # R =3,73% 19

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The method provides high quality triangulations with thousands of geometric primitives; The generated mesh is conforming, although it is not well shaped; Achieved good frame rates on PC platforms, such as 47fps (PII 450MHz, Sthealth II AGP); Critical future issues include level of detail rendering and efficient paging mechanism, which will allow rendering height fields that do not entirely fit into RAM. 20

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