Generating and Caching 3D-Tiles for Large-Scale 3D-Visualization GeoSharing , Bern, Switzerland

Transcription

1 Generating and Caching 3D-Tiles for Large-Scale 3D-Visualization GeoSharing , 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

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

4 Demo Time Institute of Geomatics Engineering 2 November

5 Layers / Contents Imagery / Elevation POIs 3D Models HTML5 Canvas Element Overlays Point Clouds Institute of Geomatics Engineering 2 November

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 Mio. km 2 (~ 29%) Water area of around Mio. km 2 (~ 71%) If we had a global dataset with 25cm 2 / Pixel: Land area (uncompressed) around 170 Petabytes Institute of Geomatics Engineering 2 November

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

8 2D Maps Quadtree structure 256 (Image courtesy of Microsoft, Bing Maps) Institute of Geomatics Engineering 2 November

9 "Web Mercator" / "Popular Visualization Pseudo Mercator" Min/Max Latitude at around +-85 degrees (-> square map...) Projection: Sphere (!) with radius of m 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: ) Projektion Projektion Sphere (!!!) Ellipsoid (virtual Globe) Institute of Geomatics Engineering 2 November

10 The Step to 3D Basically the same like 2D, however: The View Frustum contains different LOD Level of detail depends on camera position. Elevation data can be displayed (change of perspective) Institute of Geomatics Engineering 2 November

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

12 3D Tiles? Institute of Geomatics Engineering 2 November

13 OpenWebGlobe: 2.5D Elevation Tiles (Level of Detail) Institute of Geomatics Engineering 2 November

14 OpenWebGlobe: 3D-Geometry Tiles (from OSM data) Image courtesy of BTh Hürbi/Daettwyler, 2013 Institute of Geomatics Engineering MapData OpenStreetMap contributors 2 November

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 Points / Voxels per Tile (Point Cloud) max. 1 index list and max. 1 vertex list (-> GPU) optimized textures (for example by using Texture Atlas) Example: 1-3 Textures per Tile (-> GPU) Texture coordinates for other image layer(s) Institute of Geomatics Engineering 2 November

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

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

18 Example of 3DPS for a 3D Service running in the Web Browser Institute of Geomatics Engineering 2 November

19 Other Data Sources Generate tiles on the Cloud: Traditional Solution WMS, WMTS, TMS,... Postgres / PostGIS 3DPS (in Future) download visible data fragments (tiles) (Web-) Viewer HTML5 JavaScript WebGL for 3D Generate many many many many many many many many many many tiles Upload Raw data to Cloud (or web server) Raw: Image, Elevation, 3D- Models, Point Clouds,... Institut Vermessung und Geoinformation

20 Generate tiles in the Cloud: On-The-Fly Tile Generation Institute of Geomatics Engineering 2 November

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

22 Questions? MapData MapPuls, ASTER GDEMv2, Landsat Institute of Geomatics Engineering 2 November