Visualization Tools for Adaptive Mesh Refinement Data

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Visualization Tools for Adaptive Mesh Refinement Data. Gunther H. Weber 1 , Vincent E. Beckner 1 , Hank Childs 2 , Terry J. Ligocki 1 , Mark C. Miller 2 , Brian Van Straalen 1 and E. Wes Bethel 1 1 Lawrence Berkeley National Laboratory 2 Lawrence Livermore National Laboratory. Outline. - PowerPoint PPT Presentation

Text of Visualization Tools for Adaptive Mesh Refinement Data

  • Visualization Tools for Adaptive Mesh Refinement DataGunther H. Weber1, Vincent E. Beckner1, Hank Childs2, Terry J. Ligocki1, Mark C. Miller2, Brian Van Straalen1 and E. Wes Bethel11Lawrence Berkeley National Laboratory 2Lawrence Livermore National Laboratory

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • OutlineIntroduction to Berger-Colella AMR

    Visualization of Scalar AMR Data

    Specialized AMR Visualization Tools

    Visualization Tools with AMR Support

    Short overview of VisIt

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Adaptive Mesh RefinementComputational fluid dynamics techniqueTopological simplicity of regular gridsAdaptivity of unstructured meshesNested rectilinear patches, increasing resolutionReduce simulation timeReduce storage spaceBerger-Colella AMR: axis-aligned patchesVery often: Cell centered data

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Berger-Colella AMR Format

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Effective Visualization of Scalar AMR Data

    Hierarchical AMR simulationIsosurfacesDirect Volume RenderingAim: Use inherently hierarchical structure for efficient visualizationVisualizationVisualizationExtraction of continuous crack-free isosurfaces

    Effective utilization of the hierarchy for efficient renderingGood interpolation functions

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • AMR Visualization In the Beginning

    Translation of AMR to unstructured meshes [Norman et al. 1999]Visualization with standard tool (VTK, IDL, AVS)Ineffective utilization of computational resourcesDirect Volume RenderingMention AMR data without further details [Max 1993]PARAMESH [Ma 1999]ResamplingBlock-based

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Isosurfaces

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Marching Cubes and Dangling NodesMarching cubes needs vertex centered dataResample data set to vertex centered caseDangling nodes := only present in fine level (yellow + red)Choice of consistent values to avoid problems?

    Compare [Westermann, Kobbelt, Ertl 1999]Linear interpolationavoids problemsSame in coarseand fine gridNo unique valueavoids problems

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Previous Crack-fixing SolutionsMostly in context of Octree-based hierarchies[Shu et al., 1995]: Create polygon to fit crack[Shekhar et al., 1996]: Collapse polyline to line[Westermann et al., 1999]: Create triangle fan

    [Shekar et al., 1996][Westermann et al., 1999]

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • First Approach: Use of Dual GridsAvoid interpolation whenever possible!

    Avoid interpolation apart from linear interpolation along edges, which is part of marching cubes

    Use dual grid := grid formed by connecting cell centers

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Dual Grid Original Grid

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Dual Grids Both Grids

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Dual Grids

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Advantages of Dual Grid Approach

    Use of values original data for marching cubes

    No dangling nodes

    Instead: Gaps between hierarchy levels!

    Fill those gaps with stitch cells

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Stitching the GapsTessellation scheme for filling the gap between two hierarchy levelsConstraintsOnly gap region is tessellatedThe complete gap region is tessellatedOnly vertices, edges and complete faces are shared

    In 3D space: Cannot use tetrahedra because cells must share quadrilaterals as faces

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Stitching Process

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Stitch Cells 3D CaseCell FacesCell EdgesCell Vertices

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • First ResultsCoarse PatchStitch CellsFine PatchAMR simulation of star cluster formation Root level 32x32x32

    [Data set: Greg Bryan, Theoretical Astronomy Group, MIT]

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Multiple PatchesMultiple patches can be connected using the same scheme

    However: Special care must be taken with adjacent fine patches.

    Must merge adjacent grids (i. e., upgrade edges to quadrilaterals and vertices to edges)

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Multiple Patches Example

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Multiple Patches Example

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Multiple Patches Example

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Multiple Patches Cell FacesPyramid (2 basis configurations):Unrefined coarse grid point No changeRefined coarse grid point Becomes cuboid

    Triangle prism (3 basis configurations):All coarse grid points unrefined No changeOne refined coarse grid pointBoth coarse grid points refined Becomes cuboid

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Multiple Patches Fine Edge to Coarse EdgesAll coarse grid points unrefinedTwo neighboring coarse grid points refinedTwo diagonally opposed coarse grid points refinedAll coarse grid points refined

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Multiple Patches (3D) Remaining CasesAll remaining cases consider 8 verticesQuadrilateral Cell

    Actual vertex positions irrelevant!

    Information per vertex: refined or unrefined?

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Multiple Patches (3D) Generating TessellationsDraw cell to tessellate as a cubeMark each vertex as refined or unrefinedUse canonical subdivisions for boundary faces

    Use implied tessellation for cellIf more than one tessellation is possible, use arbitrary oneCoarse patchFine patch

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Multiple Patches Example Tessellation

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Multiple Patches Example Tessellation

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Reducing Amount of CasesQuadrilateral to quadrilateral (16 cases)No reduction necessaryEdge to quadrilaterals (64 cases)Upgrade to quadrilateral case (-24 cases)In certain cases: Can consider two independent triangular prisms (- 14 cases)26 cases (- further symmetry considerations)Vertex to QuadrilateralsEither upgrade to edge case or consider three pyramids independently

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Problem Case

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Problem Case

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Isosurface - One LevelAMR simulation of star cluster formation Root level 32x32x32

    [Data set: Greg Bryan, Theoretical Astronomy Group, MIT]

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Isosurface - Two LevelsAMR simulation of star cluster formation First levelStitch cells (1/2)Second level

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Isosurface - Three LevelsAMR simulation of star cluster formation

    First levelStitch cells (1/2)Second levelStitch cells (2/3)Third level

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Second Approach: Keep GridVertex/node centered dataRetain identity of cells (debugging)Subdivide boundary cells into pyramidsEliminates non-linear hanging nodesStandard isosurface techniques for pyramids

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • 2D CaseForms basis of 3D caseSplit cell faces to eliminate hanging nodes along edgesObtain values at newly created hanging by linear interpolation

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • 2D ResultsExtracted contourCells due to added samples

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • 3D Cell Face SubdivisionSubdivide lower-resolution cell face to match higher resolution faceSubdivide cell face to eliminate hanging nodes

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • 3D Cell SubdivisionSubdivide cell into pyramids with common apex point

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Second Approach Results

    Cells: 44,332Triangles: 10,456Cells: 74,358Triangles: 14,332 Time: 2.30 sec

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Second Approach Results

    Cells: 303,759Triangles: 77,029Cells: 680,045Triangles: 78,127 Time: 7.73 sec

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Volume Rendering

    Current State of the Art in Adaptive Mesh Refinement Visualization

  • Hardware-accelerated Preview of AMR DataInteractive DVR for choosing view point and transfer function