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

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

3. 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

4. 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

5. 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

6. 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)

7. Digital Elevation Model (2 n x 2 m ) 6

8. 7 h=2 2. Terrain Model

9. 8 Merge Criteria: #1 #2

10. 2. Terrain Model 9

11. 10

12. 11

13. 12

14. Sorted Unsorted 13

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

16. DEM (1.024 x 1.024) h=7 32.768 triangles 11.254 triangles #=34,34% # R =16,71% h=6 8.192 triangles 3.078 triangles #=37,57% # R =9,76% h=5 2.048 triangles 1.216 triangles #=59,375% # R =4,80% 15

17. No cracks, no T-junctions Global treatment 16

18. No cracks, no T-junctions Global treatment 17

19. DEM (2.048 x 2.048) =4,18 m h=7 32.768 triangles 15.802 triangles #=48,22% # R =16,03% h=6 8.192 triangles 5.278 triangles #=64,43% # R =8,84% h=5 2.048 triangles 1.648 triangles #=80,47% # R =4,51% 18

20. DEM (1.024 x 1.024) =8,125 m h=7 32.768 triangles 26.092 triangles #=79,62% # R =12,47% h=6 8.192 triangles 7.016 triangles #=85,64% # R =7,69% h=5 2.048 triangles 1.870 triangles #=91,30% # R =3,73% 19

21. 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