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3D Generalization Lenses (IV 2008)


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3D Generalization Lenses (IV 2008)

  1. 1. Matthias Trapp , Tassilo Glander, Henrik Buchholz, Jürgen Döllner Hasso-Plattner-Institut, University of Potsdam Germany 12 th International Conference Information Visualization 9-11 July 2008 3D Generalization Lenses for Interactive Focus + Context Visualization of Virtual City Models
  2. 2. Motivation – Virtual 3D City Models <ul><li>Properties: </li></ul><ul><ul><li>Large number of objects </li></ul></ul><ul><ul><li>High degree of visual detail </li></ul></ul><ul><ul><li>Tool for communicate complex 3D geoinformation </li></ul></ul><ul><ul><li>Numerous applications </li></ul></ul><ul><ul><li> Can lead to perceptional and cognitive overload </li></ul></ul>
  3. 3. Motivation – Generalized Virtual 3D City Models [Glander, ACMGIS 2007, ICA WS 2008]
  4. 4. Motivation – Combined Generalization Levels <ul><ul><li>Simple case: </li></ul></ul><ul><ul><li>Single arbitrarily shaped, non-convex volume (lens shape) </li></ul></ul><ul><ul><li>Two Levels of Abstraction (LOA) </li></ul></ul><ul><ul><li>Model Complexity < 500 MB (Geometry + Textures) </li></ul></ul>Context (LOA 1 ) 3D Lens Shape Single Focus (LOA 0 )
  5. 5. Motivation – Combined Generalization Levels <ul><ul><li>Comlex case: </li></ul></ul><ul><ul><li>3 intersecting lens shapes (multiple foci) </li></ul></ul><ul><ul><li>Three Levels of Abstraction </li></ul></ul><ul><ul><li>Model Complexity > 2GB </li></ul></ul>
  6. 6. Outline <ul><li>Related Work </li></ul><ul><li>Conceptual Overview </li></ul><ul><li>Preprocessing & Focus + Context Mappings </li></ul><ul><li>Real-Time Rendering </li></ul><ul><li>Application Examples </li></ul><ul><li>Future Work & Conclusions </li></ul>
  7. 7. Related Work <ul><li>Interactive 3D Focus + Context Visualization with Lenses </li></ul><ul><ul><li>3D Magic Lenses Viega et. al, UIST 1996 </li></ul></ul><ul><ul><li>A Solution for the Focus and Context Problem in Geo-Virtual Environments Ropinski et. al, DMGIS 2005 </li></ul></ul><ul><ul><li>Real-Time Volumetric Tests Using Layered Depth Images Trapp and Döllner, Eurographics 2008 </li></ul></ul><ul><li>Generalization </li></ul><ul><ul><li>2D Building Simplification & Aggregation e.g., Mayer, ISPRS 1998 </li></ul></ul><ul><ul><li>Single 3D Building Simplification e.g., Kada, ISPRS WS 2006 </li></ul></ul><ul><ul><li>3D Cell-Based City Model Generalization Glander and Döllner, ACMGIS 2007 </li></ul></ul>
  8. 8. Our Approach: Conceptual Overview <ul><li>Preprocessing Phase: </li></ul><ul><ul><li>Create levels of abstraction ( LOA ) and volumetric depth sprites ( VDS ) </li></ul></ul><ul><li>Rendering Phase: </li></ul><ul><ul><li>Create / modify focus + context mapping: FNC = map( VDS , LOA ) </li></ul></ul><ul><ul><li>Real-time image synthesis: render(FNC) </li></ul></ul>
  9. 9. Automatic Generalization of Virtual 3D City Models <ul><li>Input: City Model CM </li></ul><ul><li>Output: Levels of Abstraction LOA </li></ul><ul><li>Process: </li></ul>
  10. 10. Preprocessing of Lens Volumes <ul><li>Input: Derived or modeled solid polygonal shapes: S </li></ul><ul><li>Output: Volumetric Depth Sprites VDS </li></ul><ul><li>Processing: </li></ul>
  11. 11. Mapping Generalization Levels to Lens Volumes <ul><li>Mapping for n lenses and generalization levels: </li></ul><ul><li>Mapping Properties: </li></ul><ul><ul><li>Prioritized, hierarchical one-to-one mapping ( i = priority) </li></ul></ul><ul><ul><li>Additional attributes (colors, lens positioning & scaling,…) </li></ul></ul><ul><ul><li>Mapping can be changed at run-time </li></ul></ul>
  12. 12. Real-time Rendering of Focus + Context Mapping <ul><li>Multi-pass rendering + clipping against VDS: </li></ul><ul><ul><li>First pass: render context </li></ul></ul><ul><ul><li>Successively: one pass per LOA </li></ul></ul><ul><ul><li>Start with lowest priority: i = n </li></ul></ul>
  13. 13. Applications Examples & Usage Scenarios <ul><li>Scene Lens with intersecting foci of multiple non-convex volumes </li></ul>
  14. 14. Applications Examples & Usage Scenarios <ul><li>Camera Lens with nested foci of the same convex volume </li></ul>
  15. 15. Limitations & Future Work <ul><li>Current conceptual limitations: </li></ul><ul><ul><li>Only one-to-one mapping possible </li></ul></ul><ul><ul><li>Model complexity requires out-of-core rendering </li></ul></ul><ul><li>Clipping limitations: </li></ul><ul><ul><li>Under-sampling / aliasing artifacts </li></ul></ul><ul><ul><li>No capping of clipped areas </li></ul></ul><ul><li>Future Work: </li></ul><ul><ul><li>Extend mapping mechanism: one-to-many </li></ul></ul><ul><ul><li>Compensate sampling artifacts </li></ul></ul><ul><ul><li>Enable capping of clipped areas </li></ul></ul><ul><ul><li>Use cases that exploit technical potential </li></ul></ul>
  16. 16. Conclusions <ul><li>Wrap-up: </li></ul><ul><ul><li>Concept + technique for combing different levels of generalization </li></ul></ul><ul><ul><li>Two phase process: preprocessing + rendering </li></ul></ul><ul><ul><li>Hierarchical focus + content mapping </li></ul></ul><ul><ul><li>Interactive multi-pass rendering </li></ul></ul><ul><ul><li>Potential for future work </li></ul></ul>
  17. 17. Thank You… <ul><li>Contact: </li></ul><ul><li>Matthias Trapp [email_address] </li></ul><ul><li>Tassilo Glander </li></ul><ul><li>[email_address] </li></ul><ul><li>Henrik Buchholz </li></ul><ul><li>[email_address] </li></ul><ul><li>Computer Graphics Systems Group Prof. Dr. Jürgen Döllner </li></ul><ul><li>Researchgroup 3D-Geoinformation </li></ul>
  18. 18. Main References <ul><li>Glander, Döllner, Cell-Based Generalization of 3D Building Groups with Outlier Management , ACMGIS, 2007 </li></ul><ul><li>Kada: 3D Building Generalization Based on Half-Space Modeling , Proceedings of the ISPRS Workshop on Multiple Representation and Interoperability of Spatial Data, 2006 </li></ul><ul><li>Mayer: Model-Generalization of Building Outlines on Scale-Spaces and Scale-Space Events , International Archives of Photogrammetry and Remote Sensing, Vol. 33, 1998 </li></ul><ul><li>Trapp, Döllner, Real-Time Volumetric Tests Using Layered Depth Images, Eurographics 2008 </li></ul>