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Visualization of Scanned Cave Data with Global Illumination

This project aims to create a near-realistic visualization of 3D cave scans using global illumination. The visualization includes unstructured point clouds with diffuse color and normals, providing interactive framerates for real-time exploration.

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Visualization of Scanned Cave Data with Global Illumination

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  1. Visualization of Scanned Cave Data with Global Illumination Nico Schertler, Mirko Salm, Joachim Staib, Stefan Gumhold TU Dresden, Chairof Computer Graphics andVisualization, Germany

  2. Goal Directvisualizationof 3D cave scans: Unstructuredpointcloudswith diffuse colorandnormals Nearrealisticvisualizationforcommunicationpurposes. Interactive frameratesforrealtimeexploration. SphericalSurfels (Screen Space Hole FillingPossible) Global Illumination Hierarchicaldatastructures

  3. Global Illumination forCaveVis LocalLightingOnly LocalLighting + Ambient Term Global Illumination

  4. Global Illumination forCaveVis LocalLighting + Ambient Term Global Illumination

  5. Basic Idea – Diffuse Light Reflection When light hits a surface, reflectedintensityis uniform in everydirection. Reflected light canagainilluminateotherpartsofthescene. Idea: Model light distribution in a voxelizedscenerepresentation, whereeachvoxelstorestheemittedradiance. Simulate light transport in thevoxelrepresentation. Duringrendering, lookupradiance in theaccordingvoxels via interpolation.

  6. OverviewoftheVisualizationProcess Input Point Cloud • VoxelRepresentation • Diffuse Color • Opacity • Normal Distribution • Reflected Light Light Simulation Final Rendering

  7. Not OverviewoftheVisualizationProcess

  8. Building a VoxelRepresentation Eachinputpointisassigned a cubical Region ofInfluencebased on thesamplingdensity. Geometryattributesaresplattedadditivelyintotheoverlappingvoxelswith proper weights. This representationallowscontinuoussamplingofgeometryattributes via interpolation.

  9. Light Simulation • Injectdirect light intovoxelrepresentation. • Evaluatedirect light analytically at everyleafnode. • Useshadowmappingforocclusions. • Add tothevoxel‘salreadyexisting light information. • Mipmapthe light information. • SparseVoxelOctree • Propagate light via a gatheringprocess. • VoxelConeTracing (VCT)

  10. Light Mipmapping InnernodesoftheSparseVoxelOctreecontain:Reflected lightOpacity Innernodesareanisotropic (radiance per facet) Convertisotropicvoxelstoanisotropiconesbasedon NDF (prevent light fromshiningthroughsurfaces): NDF

  11. Light Propagation Reflected light ofvoxelscanbecalculatedbyintegratingoverthehemispheredefinedbythe NDF. Approximatethe integral withfewcones. PerformVoxelConeTracing. Usecoarsermipmapsfor sample pointsthatarefartheraway. Do Front-to-Back-Compositingforsampledradiance.

  12. Light Simulation • Injectdirect light intovoxelrepresentation. • Mipmapthe light information. • Propagate light via a gatheringprocess. Simulatesonebounceofreflection per frame. Multiple bouncesaccumulateover time.

  13. Final Rendering Renderthepointcloudassphericalsurfelswithdeferredshading. Foreachfragment: Evaluatedirect light analyticallywithshadowmaps. Useapproximated global light fromvoxelrepresentation. Optional: Trace an additional coneforspecular BRDFs.

  14. SpecularShading Diffuse Only SpecularShading

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