Storage, Maintenance and Dissemination of Massive 3D City Objects

Transcript

1. Storage, Maintenance and Dissemination of Massive 3D City Objects Kavisha 31-05-2016 3D4EM Meeting
2. Terrain as TIN
3. Terrain as Raster
4. Terrain as TIN + Grid
5. What we have??
6. Challenges with current solution: CityGML
7. Voluminous data • CityGML 3DTOPNL Terrains : TIN : ~700 GB (1 billion triangles) ( x 1 , y 1 , z 1) ( x 2 , y 2 , z 2) ( x 3 , y 3 , z 3) < gml : triangle > < gml : exterior > < gml : LinearRing > < gml : posList > x 1 y 1 z 1 x 2 y 2 z 2 x 3 y 3 z 3 x 1 y 1 z 1 < /gml : posList > < gml : LinearRing > < gml : exterior > < gml : triangle > OGC Simple Feature No referencing No TIN topology
8. No distinct LODs
9. Problems • No support for terrain topology in: • CityGML TINRelief and • CityGML MassPointRelief
10. Nothing for Tiling Unsafe Triangles Tile 1 Tile 2 Tile 3 Tile 4 Tile Boundary Triangles spanning multiple tiles
11. Skeptical TIN !! Why separate class??
12. Grids : vague!! • Raster/Grid terrains in CityGML. GML schema Vague?? No sample data!!
13. Terrain as TIN + Grid TIN Relief Grid Coverage validity polygon Not at the centre of grid cell
14. Not suitable for 3D Viz
15. Framework
16. What needs to be done? • Redefinition of conceptual model of geometry in the CityGML schema for terrains.
17. What needs to be done? P1 P2 P3 …
18. Terrains@CityGML
19. Terrain@CityGML • CityGML 3DTOPNL Terrains : ~700 GB (1 billion triangles) • For 1 tile: • CityGML: ~ 740 MB • Terrains@CityGML: ~ 30 MB ~25x less storage space Compressed workable file (~5 to 7 MBs for 1 tile)
20. CityGML vs Terrain@CityGML
21. Really Triangles??: YES
22. Terrains@CityGML with Cesium
23. 3D over Cesium • A s g e o m e t r y ( P o l y g o n / B o x / C y l i n d e r / Rectangle,..etc.)
24. 3D over Cesium • A s g e o m e t r y ( P o l y g o n / B o x / C y l i n d e r / Rectangle,..etc.) Coordinates
25. 3D over Cesium • A s g l T F ( G L Tr a n s m i s s i o n F o r m a t ) : Interoperability??
26. A way around glTF Terrains@CityGML Parser JSON Description file Binary data file Textures Cesium API 30 MB 8 KB 24 MB
27. As Quantized Mesh • At present: • only height maps for Rasters • No TIN implementation Terrains@CityGML Generate Quadtree Cesium API Generate header .terrain tiles Cesium Terrain Server
28. Terrains @Cesium • As Quantized mesh • indexed triangles as quad pyramids of height maps
29. PDOK@Cesium
30. PDOK @Cesium
31. Thank you!!!