OpenWebGlobe - GeoSharing Bern
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  • 1. Generating and Caching 3D-Tiles for Large-Scale 3D-Visualization GeoSharing 02.11.2013, Bern, Switzerland Martin Christen, Robert Wüest, Benjamin Loesch, Stephan Nebiker FHNW – University of Applied Sciences and Arts Northwestern Switzerland Institute of Geomatics Engineering
  • 2. WebGL • Web Graphics Library (based on OpenGL ES 2.0) • Rendering interactive 2D/3D graphics within the webbrowser • Optimized for JavaScript • Hardware acceleration using the Graphics Processing Unit (GPU) • WebGL programs consist of: • application code written in JavaScript (CPU) and • shader code (GLSL) for the GPU • No plugin for these (desktop) browsers: (11+) Institute of Geomatics Engineering 2 November 2013 2
  • 3. • Virtual Globe without plugins for modern webbrowsers. • Open Source Project started in April 2011 (based on C++ version started in 2005) • Created by FHNW - University of Applied Sciences Northwestern Switzerland (Institute of Geomatics Engineering) • Uses HTML5 and WebGL • JavaScript Library for rapid development of web-based 3D geoinformation applications • Full integration into customer web sites • Runs on Windows, MacOS X, Linux • Targets Desktop and Mobile Devices* Institute of Geomatics Engineering 2 November 2013 3
  • 4. Demo Time http://world.openwebglobe.org http://swiss3d.openwebglobe.org Institute of Geomatics Engineering 2 November 2013 4
  • 5. Layers / Contents • Imagery / Elevation • POIs • 3D Models • HTML5 Canvas Element • Overlays • Point Clouds Institute of Geomatics Engineering 2 November 2013 5
  • 6. Global Datasets in 2D First we need to understand how global 2D maps work. OpenStreetMap, Google Maps, Bing Maps, ... Theoretical example Earth: – Land area of around 148.9 Mio. km2 (~ 29%) – Water area of around 361.2 Mio. km2 (~ 71%) If we had a global dataset with 25cm2 / Pixel: – Land area (uncompressed) around 170 Petabytes Institute of Geomatics Engineering 2 November 2013 6
  • 7. 2D Tiles Always one zoom level visible User zooms in/out (GUI / mouse wheel) only required data ("visible data") is requested from the server (or cloud) Screenshots from Google Maps Institute of Geomatics Engineering 2 November 2013 7
  • 8. 2D Maps – Quadtree structure 256 Institute of Geomatics Engineering (Image courtesy of Microsoft, Bing Maps) 2 November 2013 8
  • 9. "Web Mercator" / "Popular Visualization Pseudo Mercator"  Min/Max Latitude at around +-85 degrees (-> square map...)  Projection: Sphere (!) with radius of 6378137m  Invented by Google, unfortunatly many web maps use it today (Reason was performance, but that is not really the case)  "almost conformal" projection.  EPSG:3857 (don't use EPSG: 900913) Projektion Sphere (!!!) Institute of Geomatics Engineering Projektion Ellipsoid (virtual Globe) 2 November 2013 9
  • 10. The Step to 3D Basically the same like 2D, however: 256 The View Frustum contains different LOD 256 Level of detail depends on camera position. Elevation data can be displayed (change of perspective) 256 256 Institute of Geomatics Engineering 2 November 2013 10
  • 11. Some Tile Types 2D Image Tile contents: 256x256 Pixels (in most cases) (May also contain rasterized vectors etc.) 2D Vector Tile contents: 2D Geometry (Number of Elements limited for LOD) 2D Elevation Tile contents: Elevation values (e.g. numbers) contents 17x17 values (or similar). Institute of Geomatics Engineering 2 November 2013 11
  • 12. 3D Tiles ? Institute of Geomatics Engineering 2 November 2013 12
  • 13. OpenWebGlobe: 2.5D Elevation Tiles (Level of Detail) Institute of Geomatics Engineering 2 November 2013 13
  • 14. OpenWebGlobe: 3D-Geometry Tiles (from OSM data) Image courtesy of BTh Hürbi/Daettwyler, 2013 Institute of Geomatics Engineering MapData © OpenStreetMap contributors 2 November 2013 14
  • 15. 3D Tiles: Block of Geometry / Scenegraph A 3D Tile contains: • optimized 2D/3D Geometry (simplified for current LOD) Examples: max. 500 triangles per Tile max. 1000 Points / Voxels per Tile (Point Cloud) max. 1 index list and max. 1 vertex list (-> GPU) • optimized textures (for example by using Texture Atlas) http://wiki.polycount.com/TextureAtlas Example: 1-3 Textures per Tile (-> GPU) • Texture coordinates for other image layer(s) Institute of Geomatics Engineering 2 November 2013 15
  • 16. 3D Standards Existing Standards: • KML / COLLADA – Not optimized for rendering! • CityGML – Not optimized for rendering! • X3D/X3DOM – Not optimized for rendering! • ... Coming soon: • OGC 3D Portrayal Service (3DPS) [in development] • glTF – Transmission format for WebGL, OpenGL ES, and OpenGL. optimized for rendering – [in development] Institute of Geomatics Engineering 2 November 2013 16
  • 17. 3D Portrayal Service (3DPS) Goal: Develop a standard service interface to visualize very large 3D geospatial datasets online via Web-Browser and Mobile Devices. Content delivery includes 3D Scenegraph as well as image based rendering (Formats: X3D, COLLADA; for web browsers: X3DOM, XML3D, JSON) Institute of Geomatics Engineering 2 November 2013 17
  • 18. Example of 3DPS for a 3D Service running in the Web Browser Institute of Geomatics Engineering 2 November 2013 18
  • 19. Other Data Sources Generate tiles on the Cloud: Traditional Solution download visible data fragments (tiles) WMS, WMTS, TMS, ... Postgres / PostGIS 3DPS (in Future) Generate many many many many many many many many many many tiles (Web-) Viewer HTML5 JavaScript WebGL for 3D Upload Raw data to Cloud (or web server) Raw: Image, Elevation, 3DModels, Point Clouds, ... Institut Vermessung und Geoinformation 02.11.2013 19
  • 20. Generate tiles in the Cloud: On-The-Fly Tile Generation Institute of Geomatics Engineering 2 November 2013 20
  • 21. Conclusion • OpenWebGlobe • 2D & 3D Tiles... almost the same... but very different • Computer Graphics & Geo community need to work together when creating 3D Standards. • We need Standards for rendering efficiently. • Different approach for creating (3D-) Tiles using current standards. Institute of Geomatics Engineering 2 November 2013 21
  • 22. Questions ? MapData © MapPuls, ASTER GDEMv2, Landsat http://www.openwebglobe.org Institute of Geomatics Engineering 2 November 2013 22