Non-Planar Projection GRAPP 2008

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This paper presents a novel image- based approach to efficiently generate real- time non- planar projections of arbitrary 3D scenes such as panorama and fish- eye views. The real- time creation of such projections has a multitude of applications, e

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BBB: 

BBB Computer Graphics Systems Group, Hasso-Plattner Institute, University of Potsdam,

Outline: 

Outline ¨ Introduction & Basic Concepts ¨ Generalization Concept ¨ Implementation ¨ Applications ¨ Conclusions

Mission: Unified Rendering Technique: 

Mission: Unified Rendering Technique Unify techniques for: Non-planar projections 2D lens effects Image warping Implementation requirements: Real-time visualization Large scene rendering Single projection center (SCOP)

Basic Concept – Overview : 

Basic Concept – Overview Components: Dynamic cube map Screen-aligned quad Fragment shader 3-Phase rendering: Create/Update dynamic cube map Setup projection shader Render screen-aligned quad Main characteristics: Image-based approach Fully hardware accelerated Cube map

Basic Concept – Details : 

Basic Concept – Details Define projection function: Apply camera orientation: Sample from cube map:

Example: Cylindrical Projection: 

Example: Cylindrical Projection Projection function: Horizontal Vertical Horizontal FOV: 360°, Vertical FOV 60°

Example: Spherical Projections: 

Example: Spherical Projections Projection function: Viewport truncation: A B C

Optimization: Normal Maps: 

Optimization: Normal Maps For static projection functions Store normalized cube map sampling vectors Using Render-To-Texture (RTT) Floating point texture precision

Outline: 

Outline þ Introduction & Basic Concepts ý Generalization Concept ¨ Implementation ¨ Applications ¨ Conclusions

Generalization Concept – Overview : 

Generalization Concept – Overview A B C D

Projection Tile Screen - Example: 

Projection Tile Screen - Example Final Rendering

Projection Tile Screens: 

Projection Tile Screens Projection tile screen (TPS)=set of projection tiles Projection tile=set of tile features Tile Feature:

Generating Feature Maps: 

Generating Feature Maps Feature-map rendering: Setup render-to-texture Setup orthogonal-projection Encode feature properties as color values: Angles: Render tiles successively Cube map sampling vectors: Calculated using fragment shader Vector derived by:

Projection Tiles – Extensions : 

Projection Tiles – Extensions Limitations: PTS is hard to model and control Triangulation influences interpolation Covers not all possible tile shapes No hard transition between tiles Improvements: Regular grid  triangulated planar mesh („triangle soup“) Enables hard transitions between tiles Enable the usage of modeling tools

Outline: 

Outline þ Introduction & Basic Concepts þ Generalization Concept ý Implementation ¨ Applications ¨ Conclusions

Dynamic Cube Maps: 

Dynamic Cube Maps Single-Pass: needs DX10 compatible hardware Evaluate the scene only once Geometry shader multiply primitive Project primitive to cube map faces Rasterization to six texture layers in parallel Multi-Pass: most compatible approach Evaluate scene six times RTT to each cube face Runtime optimizations: Omit whole cube map update Omit cube map side update

Main Shader: 

Main Shader Shader main entry point

Cylindrical Projection Shader: 

Cylindrical Projection Shader Projection function

Outline: 

Outline þ Introduction & Basic Concepts þ Generalization Concept þ Implementation ý Applications ¨ Conclusions

Non-Planar Projection Surfaces: 

Non-Planar Projection Surfaces Horizontal FOV: 360°, Vertical FOV 90° Normal Map Final Rendering

Using Custom Normal Maps: 

Using Custom Normal Maps Final Rendering Horizontal FOV: 90°, Vertical FOV 60°

Combinations of Projections: 

Combinations of Projections

Lens Effects: 

Lens Effects Horizontal FOV: 180°, Vertical FOV 135° Final Rendering Normal Map

Compound Eye: 

Compound Eye Horizontal FOV: 120°, Vertical FOV 60°

Outline: 

Outline þ Introduction & Basic Concepts þ Generalization Concept þ Implementation þ Applications ý Conclusions

Limitations: 

Limitations Rendering quality depends on: Cube map resolution Tessellation of tile screen Undersampling / Oversampling Dynamic cube map can be costly Interpolation artifacts by contrary tessellation Haik Lorenz, Jürgen Döllner, Dynamic Mesh Refinement on GPU using Geometry Shaders, WSCG 2008 (to appear) A B

Conclusions: 

Conclusions Take aways: General concept for SCOP distortions: Non-planar projections 2D lenses with arbitrary shapes Image warping and distortions Applicable in real-time for large scenes Controllable via projection tile screens Important: resolution of cube map and tessellation of PTS Future work: Improve rendering quality Develop graphical user interface for PTS Shift PTS tessellation to GPU

Q & A: 

Q & A Thank You. Contact: Matthias Trapp matthias.trapp@hpi.uni-potsdam.de Computer Graphics Systems Group Prof. Dr. Jürgen Döllner www.hpi.uni-potsdam.de/3d Research group 3D-Geoinformation www.3dgi.de