1. Enhancing Interactive Non-Planar Projections of 3D Geovirtual Environments with Stereoscopic Imaging Matthias Trapp, Haik Lorenz, Markus Jobst, Jürgen Döllner Hasso-Plattner-Institute at the University of Potsdam True-3D in Cartography 1st International Conference on 3D MapsAugust 24 - 28, 2009 Dresden, Germany 1

2. motivation geo-media technology provides interactivity, immersion facilitatesthecommunication of 3D geospatialdata applications to cartography: increase immersion into 3D geovirtual environments support for depth-cues planar stereoscopy: well understood – rendering: straight forward supported by graphics hardware / driver non-planar stereoscopy: provides high field-of-view and image resolution 2

3. problem: non-planar projection surfaces rendering of digital 3D city and landscape models: high amount of geometry and texture data real-time constraints (> 20 frames per second) current generation of graphics hardware (GPU) no native support for non-planar projection surfaces requires specific rendering techniques classified into image, geometry, and ray-based approaches hardware-accelerated stereoscopic imaging: available stereo hardware modifies vertex pipeline stage cannot be used for rendering non-planar stereoscopy 3

4. framework - conceptual overview 4

5. review: image-based approach (IBA) basic concept: dynamic cube map + screen-aligned quad image warping based on normal vectors: 3-phase rendering process: create/update dynamic cubemap setup projection shader render screen-aligned quad 5

6. adapting IBA for stereoscopy basic idea for image-based non-planar projections: create cubemaps for each virtual camera derive non-planar projection for each cube-map examplary workflow for two stereo mates: 6

7. review: geometry-based approach (GBA) projection computed on a per-vertex basis ensure sufficient on-screen vertex density dynamic mesh refinement required 7

8. adapting GBA for stereoscopy straight forward approach: setup piece-wise projection for each virtual camera render into different color-buffers additional post-processing step: layer compositing example for stereo image pairs: 8

9. rendering active & passive stereo active stereo: using quad-buffering usually encapsulated by graphics driver passive stereo: anaglyph: color-buffer compositing polarized: render to framebuffer chromo-depth stereo: apply directly during rendering 9

10. rendering passive anaglyph - results HITIT 10

11. rendering chromo-stereoscopy no need for generating stereo image pair color as a function of depth 11

12. rendering chromo-stereoscopy - results HITIT 12

13. applying chromo-stereoscopy GBA: straight forward application to fragment‘s depth IBA: needs depth correction 13

14. renderingchromo-stereoscopy - results HITIT 14

15. chroma-stereoscopy issues common problems for IBA and GBA: distribution of color can decrease stereo effect perception: facade information (texture) is altered interaction: focal plane must be adapted 15

16. binarycomparision GBA vs. IBA 16

17. conclusions & future work conclusions: interactive stereoscopic rendering for non-planar projections increases immersion, thus psychological depth cues performance limited by geometric complexity of the scene GBA outperforms IBA but IBA much easier to implement/use open problem: omni-directional stereo without image artifacts future work: auto stereoscopy for non-planar projections surfaces eye tracking to adjust user‘s focal plane 17

18. Thank you for your attention! Questions? Contact Matthias Trapp matthias.trapp@hpi.uni-potsdam.de Haik Lorenzhaik-lorenz@hpi.uni-potsdam.de Markus Jobst office@jobstmedia.at JürgenDöllner juergen.doellner@hpi.uni-potsdam.de Workgroup 3D Geoinformation www.3dgi.de/ Computergraphics System Group www.hpi.uni-potsdam.de/doellner/ 18