Slide 1:Interactive Stereo Rendering For Non-Planar Projections of 3D Virtual Environments :: Matthias Trapp et al. :: GRAPP 2009 1 Interactive Stereo RenderingFor Non-Planar Projections of 3D Virtual Environments Matthias Trapp, Haik Lorenz, Jürgen Döllner Hasso-Plattner-Institute, University of Potsdam, Germany GRAPP 2009International Conference on Computer Graphics Theory and Applications Lisboa, Portugal


Motivation :Interactive Stereo Rendering For Non-Planar Projections of 3D Virtual Environments :: Matthias Trapp et al. :: GRAPP 2009 2 Motivation Immersive Digital Environments: … Real-time rendering High field-of-view Stereoscopy … Non-planar projections: Not supported by rendering hardware Single-center of projection only Contribution: Feasibility study for stereoscopy of non-planar projections Compare image-based & geometry-based approaches


Anaglyph Results :Interactive Stereo Rendering For Non-Planar Projections of 3D Virtual Environments :: Matthias Trapp et al. :: GRAPP 2009 3 Anaglyph Results Cylindrical Projection


Anaglyph Results :Interactive Stereo Rendering For Non-Planar Projections of 3D Virtual Environments :: Matthias Trapp et al. :: GRAPP 2009 4 Anaglyph Results Spherical Projection


Rendering Non-Planar Projections :Interactive Stereo Rendering For Non-Planar Projections of 3D Virtual Environments :: Matthias Trapp et al. :: GRAPP 2009 5 Rendering Non-Planar Projections Geometry-based Approach (GBA) [Lorenz and Döllner 2008] Projection computed on a per-vertex basis Dynamic mesh refinement to ensure sufficient on-screen vertex density Requires DX 10 hardware Image-based Approach (IBA) [Trapp and Döllner 2008] Normal based image warping Dynamic cube map + screen-aligned quad Fragment shader functionality (DX 9a) GBA & IBA fully hardware accelerated


Previous Work: Image-based Approach :Interactive Stereo Rendering For Non-Planar Projections of 3D Virtual Environments :: Matthias Trapp et al. :: GRAPP 2009 6 Previous Work: Image-based Approach Projection function computes cubemap sampling normal: Example – horizontal cylindrical projection: 3-Phase rendering process: Create/update dynamic cubemap Setup projection shader Render screen-aligned quad


Stereoscopy for Non-Planar Projections :Interactive Stereo Rendering For Non-Planar Projections of 3D Virtual Environments :: Matthias Trapp et al. :: GRAPP 2009 7 Stereoscopy for Non-Planar Projections Stereo ? Image pair ? Angle & depth disparity: Planar projections: render two images using two virtual cameras Basic idea for image-based non-planar projections: Render two cubemaps (left & right eye) Derive projection image pair Implementation problem: Optimal: Single-Pass Render to Dual-Cubemap Not supported by current hardware generation Cannot bind two cubemap textures to a single active framebuffer object Work around: layered rendering using geometry shader


Single-Pass Render to Dual-Cubemap :Interactive Stereo Rendering For Non-Planar Projections of 3D Virtual Environments :: Matthias Trapp et al. :: GRAPP 2009 8 Single-Pass Render to Dual-Cubemap


Layered Rendering – Geometry Shader :Interactive Stereo Rendering For Non-Planar Projections of 3D Virtual Environments :: Matthias Trapp et al. :: GRAPP 2009 9 Layered Rendering – Geometry Shader


Layer Sampling :Interactive Stereo Rendering For Non-Planar Projections of 3D Virtual Environments :: Matthias Trapp et al. :: GRAPP 2009 10 Layer Sampling Problem: In: Normal Vector Out: 2D texture coordinates + layer ID Reference Sampling (RSA) Using Reference Cube-Map Additional memory consumptions Sampling artifacts on texture border Analytic Sampling (ASA) Re-implement OpenGL fixed-function 54 shader instructions


Stereo Rendering :Interactive Stereo Rendering For Non-Planar Projections of 3D Virtual Environments :: Matthias Trapp et al. :: GRAPP 2009 11 Stereo Rendering Applied as post-processing pass(es) Active Stereo Rendering (shutter glasses): Frame sequential Using OpenGL quad buffer Two full-screen passes (left and right eye), multiplexed in time Passive stereo rendering (anaglyph): Single full-screen pass Sampling two cubemaps and mix samples Apply color correction matrix [Zhang 2006]


IBA Performance Evaluation (Anaglyph) :Interactive Stereo Rendering For Non-Planar Projections of 3D Virtual Environments :: Matthias Trapp et al. :: GRAPP 2009 12 IBA Performance Evaluation (Anaglyph)


GBA-IBA Comparison – Rendering Performance :Interactive Stereo Rendering For Non-Planar Projections of 3D Virtual Environments :: Matthias Trapp et al. :: GRAPP 2009 13 GBA-IBA Comparison – Rendering Performance


GBA-IBA Comparison – Image Quality :Interactive Stereo Rendering For Non-Planar Projections of 3D Virtual Environments :: Matthias Trapp et al. :: GRAPP 2009 14 GBA-IBA Comparison – Image Quality GBA is superior over IBA: Cause: cubemap sampling artifacts Problematic for wireframe-rendering or hatching techniques (NPR) GBA IBA


GBA-IBA Comparison – Memory Footprint :Interactive Stereo Rendering For Non-Planar Projections of 3D Virtual Environments :: Matthias Trapp et al. :: GRAPP 2009 15 GBA-IBA Comparison – Memory Footprint GBA - View-dependent: t – input triangles r – average rate of primitive amplification i – intermediate data (i= 16) IBA – Static footprint: l – number of texture layers b – precision per color channel s – texture resolution c – number of color channels Example: 180° cylindrical projection: OGBA = ~ 69 MB ˜ l = 4, b = 4 (32bit), s = 1024, c = 4 For higher FOV: OIBA < OGBA


GBA-IBA Comparison – Binary Wrap Up :Interactive Stereo Rendering For Non-Planar Projections of 3D Virtual Environments :: Matthias Trapp et al. :: GRAPP 2009 16 GBA-IBA Comparison – Binary Wrap Up


Conclusions & Future Work :Interactive Stereo Rendering For Non-Planar Projections of 3D Virtual Environments :: Matthias Trapp et al. :: GRAPP 2009 17 Conclusions & Future Work Summary: Interactive stereoscopic rendering for non-planar projections Common upper bound = medium scene complexity (~500,000 triangles) GBA outperforms IBA IBA much easier to implement/use Future Work: Increase IBA rendering performance by re-using information IBA Image quality Derive omni-directional stereo projections


Slide 18:Interactive Stereo Rendering For Non-Planar Projections of 3D Virtual Environments :: Matthias Trapp et al. :: GRAPP 2009 18 Thank You! Questions? Contact Matthias Trapp matthias.trapp@hpi.uni-potsdam.de Haik Lorenz haik.lorenz@hpi.uni-potsdam.de Jürgen Döllner juergen.doellner@hpi.uni-potsdam.de Computer Graphics Systems Group www.hpi.uni-potsdam.de/3d Researchgroup 3D-Geoinformation www.3dgi.de