# Presentation: 131062

## Visualization Tools for Adaptive Mesh Refinement Data

**Gunther H. Weber****1****, **Vincent E. Beckner1, Hank Childs2, Terry J. Ligocki1, Mark C. Miller2, Brian Van Straalen1 and E. Wes Bethel1
- 1Lawrence Berkeley National Laboratory2Lawrence Livermore National Laboratory

## Outline

**Outline**

**Introduction 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

**Notes:**
What do I want to accomplish in this talk: Give you an overview of the research done in AMR Vis, show the current state of tools and the “disconnect” between research and implementation. Finally, I want to introduce VisIt o which I am currently working and convince you that it is worth a look.

## Adaptive Mesh Refinement

**Computational fluid dynamics technique**
**Topological simplicity of regular grids**
**Adaptivity of unstructured meshes**
**Nested rectilinear patches, increasing resolution**
**Reduce simulation time**
**Reduce storage space**
**Berger-Colella AMR: axis-aligned patches**
**Very often: Cell centered data**

- Current State of the Art in Adaptive Mesh Refinement Visualization

**Notes:**
Grid = patch

## Berger-Colella AMR Format

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Effective Visualization of Scalar AMR Data

**Effective Visualization of Scalar AMR Data**

- Hierarchical AMR simulation

- Isosurfaces

- “Direct Volume Rendering”

**Aim: Use inherently hierarchical structure for efficient visualization**

- Visualization

- Visualization

- Extraction of continuous “crack-free” isosurfaces

- Effective utilization of the hierarchy for efficient rendering
- Good 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 resources**
**Direct Volume Rendering**
**Mention AMR data without further details [Max 1993]**
**PARAMESH  [Ma 1999]**
**Resampling**
**Block-based**

- Current State of the Art in Adaptive Mesh Refinement Visualization

**Notes:**
04:00
Max: Kurze erwähnung von AMR Daten
Ma: Paralleles DVR von PARAMESH AMR Daten
Norman: Konvertierung nach unstrukturiert, AMR first class datatype
bis 05:00

Kähler: HW-accel VR, AMR for sparse volume data, Rendering Start Case Study
Park: Splatting of AMR Data

## Isosurfaces

## Marching cubes needs vertex centered data
Resample data set to vertex centered case
Dangling nodes := only present in fine level (yellow + red)
Choice of consistent values to avoid problems?

Compare [Westermann, Kobbelt, Ertl 1999]

***Resample***** data set *****to vertex centered***** case**
**Dangling nodes := only present in fine level (yellow + red)**
**Choice of consistent values to avoid problems?**
**Compare [Westermann, Kobbelt, Ertl 1999]**

- Linear interpolation
- avoids problems

**Marching Cubes and Dangling Nodes**

- Same in coarse
- and fine grid

- No unique value
- avoids problems

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Previous Crack-fixing Solutions

**Mostly 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 Grids

***“******Avoid 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

**Dual Grid – Original Grid**

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Dual Grids – Both Grids

**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 Gaps

**Tessellation scheme for filling the gap between two hierarchy levels**
**Constraints**
**Only gap region is tessellated**
**The complete gap region is tessellated**
**Only 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

**Stitching Process**

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Stitch Cells – 3D Case

- Cell Faces

- Cell Edges

- Cell Vertices

- Current State of the Art in Adaptive Mesh Refinement Visualization

**Notes:**
Kombination aus zwei 2D Fällen

## First Results

**First Results**

- Coarse Patch

- Stitch Cells

- Fine Patch

**AMR 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 Patches

**Multiple 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

**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

**Multiple Patches – Example**

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Pyramid (2 basis configurations):
Unrefined coarse grid point  No change
Refined coarse grid point  Becomes cuboid

Triangle prism (3 basis configurations):
All coarse grid points unrefined  No change
One refined coarse grid point
Both coarse grid points refined  Becomes cuboid

**Unrefined coarse grid point ******** No change**
**Refined coarse grid point ******** Becomes cuboid**
**Triangle prism (3 basis configurations):**
**All coarse grid points unrefined ******** No change**
**One refined coarse grid point**
**Both coarse grid points refined ******** Becomes cuboid**

**Multiple Patches – Cell Faces**

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Multiple Patches – Fine Edge to Coarse Edges

**All coarse grid points unrefined**

**Two neighboring coarse grid points refined**

**Two diagonally opposed coarse grid points refined**

**All coarse grid points refined**

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Multiple Patches (3D) – Remaining Cases

**All remaining cases consider 8 vertices**
**Quadrilateral 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 Tessellations

**Draw cell to tessellate as a cube**
**Mark each vertex as refined or unrefined**
**Use canonical subdivisions for boundary faces**
**Use implied tessellation for cell**
**If more than one tessellation is possible, use arbitrary one**

**Coarse patch**

**Fine 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

**Multiple Patches – Example Tessellation**

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Reducing Amount of Cases

**Quadrilateral to quadrilateral (16 cases)**
**No reduction necessary**
**Edge 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 Quadrilaterals**
**Either upgrade to edge case or consider three pyramids independently**

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Problem Case

**Problem Case**

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Problem Case

**Problem Case**

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Isosurface - One Level

**AMR 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 Levels

**AMR simulation of star cluster formation**
** **
**First level**
**Stitch cells (1/2)**
**Second level**

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Isosurface - Three Levels

**AMR simulation of star cluster formation**
**First level**
**Stitch cells (1/2)**
**Second level**
**Stitch cells (2/3)**
**Third level**

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Second Approach: Keep Grid

**Second Approach: Keep Grid**

**Vertex/node centered data**
**Retain “identity” of cells (debugging)**
**Subdivide boundary cells into pyramids**
**Eliminates “non-linear” hanging nodes**
**Standard isosurface techniques for pyramids**

- Current State of the Art in Adaptive Mesh Refinement Visualization

**Notes:**
Define boundary cells

## 2D Case

**2D Case**

**Forms basis of 3D case**
**Split cell faces to eliminate hanging nodes along edges**
**Obtain values at newly created hanging by linear interpolation**

- Current State of the Art in Adaptive Mesh Refinement Visualization

**Notes:**
  A transitional mesh region is created  between grids of different resolution by subdividing the boundary cells of the lower-resolution grid such that the  original hanging nodes are eliminated.

A cell face is split when a hanging node exists on the midpoint of an edge of a cell.  Cell faces can be  subdivided in two ways:
- A face that is a  square or that is taller than it is wide is split into three sections:  First, it is split in half, parallel to the edge  containing the hanging node.  Next, the newly created cell adjacent to the hanging node is split to eliminate the  hanging node. 
- If a cell face is not a square or tall, the face  is split into two halves along the hanging node, as shown as case b) in Figure 5.

## 2D Results

**Extracted contour**

**Cells due to added samples**

- Current State of the Art in Adaptive Mesh Refinement Visualization

**Notes:**
Add legend

## 3D Cell Face Subdivision

**3D Cell Face Subdivision**

**Subdivide lower-resolution cell face to match higher resolution face**
**Subdivide cell face to eliminate hanging nodes**

- Current State of the Art in Adaptive Mesh Refinement Visualization

**Notes:**
Dot is hanging node

## 3D Cell Subdivision

**Subdivide cell into pyramids with common apex point**

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Second Approach – Results

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

- Current State of the Art in Adaptive Mesh Refinement Visualization

**Notes:**
(Dataset courtesy of Volume Visualization System,  Computer Science Department, State University of New York, Stony Brook, New York) 
AMD 1.2 GHz Athlon, 386 MB memory VTK 4.0

## Second Approach – Results

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

- Current State of the Art in Adaptive Mesh Refinement Visualization

**Notes:**
(Dataset courtesy of Julie Coombs, Center for  Neuroscience and Department of Neurobiology, Physiology, and Behavior, University of California,  Davis)  

## Volume Rendering

## Hardware-accelerated Preview of AMR Data

**Interactive DVR for choosing view point and transfer function**
**Subdivide data set in regions of constant resolution**
**AMR Partition Tree (generalized kD-tree)**
**Traverse “AMR Partition tree” and render regions using hardware-accelerated DVR**

- Current State of the Art in Adaptive Mesh Refinement Visualization

**Notes:**
09:30

## Homogenization

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Homogenization

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Homogenization

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Homogenization

**Homogenization**

- Current State of the Art in Adaptive Mesh Refinement Visualization

## AMR Partition Tree

**Generalized kD-tree**
**Partitions data-set into regions of constant resolution**
**Node types:**
**Unrefined grid part (CU): Region is only available at resolution of current level**
**Completely refined grid part (CR): Region is completely available at next higher resolution**
**Partition node (PN): Partitions bounding box along one of the axes**

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Partition Tree – Example

- PN

- CU

- PN

- CU

- CU

- CR

- CU

- CU

- CR

- CR

- CU

- PN

- CU

- PN

- PN = Partition node along one axis

- CU = Completely unrefined region

- CR = Completely refined region =
-           Transition to next level

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Adaptive Tree Traversal

**View-dependent criteria:**
**Avoid unnecessary computation time**
**No quality loss**
**Time-dependent****	**** criteria:**
**Sacrifice render quality to obtain specified frame rate**

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Hardware-accelerated Rendering – Interactive

**Hardware-accelerated Rendering – Interactive**

**AMR 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

**Notes:**
Messungen: 2000 auf SGI Onyx
bis 11:00

## Hardware-accelerated Rendering – Maximum Quality

**AMR 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

**Notes:**
Messungen: 2000 auf SGI Onyx

## Use “cell projection” [Ma & Crockett 1997] to display individual patches
Traverse patches and construct ray segments [object space based]
Ma & Crockett: Sort ray segments

**Traverse patches and construct ray segments [object space based]**
**Ma & Crockett: Sort ray segments**

**High-quality DVR of AMR Data**

- Current State of the Art in Adaptive Mesh Refinement Visualization

**Notes:**
11:00

## Progressive DVR of AMR Data

**Progressive DVR of AMR Data**

**Bottom-up**
**Render fine grids, fill gaps with coarse grid data**

**Top-down**
**Render coarse grids (preview), replace data with finer representation**

- Current State of the Art in Adaptive Mesh Refinement Visualization

**Notes:**
bis 11:45

## Interpolation

- Bilinear

- Linear

**Interpolation**

**Nearest neighbor (constant) interpolation ****➔**** debugging**
**Piecewise Linear Method (PLM) ****➔**** Discontinuities**
**Dual grids (trilinear) and stitch cells**

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Cell-projection — Scan Convert Front Facing Boundaries

- Ray segment queues

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Piecewise Linear Method – One Hierarchy Level

**AMR 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

**Notes:**
Messungen: 2000 auf SGI Onyx

## Piecewise Linear Method – Two Hierarchy Levels

**AMR 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

**Notes:**
Messungen: 2000 auf SGI Onyx

## Piecewise Linear Method – Three Hierarchy Levels

**AMR 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

**Notes:**
Messungen: 2000 auf SGI Onyx

## Save standard element coordinates in cell vertices

**Mapping to Standard Elements (1/3)**

**World coordinates**

**Standard element coordinates**

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Interpolate standard element coordinates during rasterization

**Mapping to Standard Elements (2/3)**

**World coordinates**

**Standard element coordinates**

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Use standard element coordinates for interpolation along ray segment

**Use standard element coordinates for interpolation along ray segment**

**Mapping to Standard Elements(3/3)**

**World coordinates**

**Standard element coordinates**

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Interpolation with Stitch Cells – One Hierarchy Level

**Simulation of an Argon bubble in a surrounding gas hit by a shockwave**
**[Data set: Center for Computational Sciences and Engineering (CCSE), Lawrence Berkeley National Laboratory]**

- Current State of the Art in Adaptive Mesh Refinement Visualization

**Notes:**
DVR bis 12:30

## Interpolation with Stitch Cells – Two Hierarchy Levels

**Simulation of an Argon bubble in a surrounding gas hit by a shockwave**
**[Data set: Center for Computational Sciences and Engineering (CCSE), Lawrence Berkeley National Laboratory]**

- Current State of the Art in Adaptive Mesh Refinement Visualization

**Notes:**
DVR bis 12:30

## Interpolation with Stitch Cells – Three Hierarchy Levels

**Simulation of an Argon bubble in a surrounding gas hit by a shockwave**
**[Data set: Center for Computational Sciences and Engineering (CCSE), Lawrence Berkeley National Laboratory]**

- Current State of the Art in Adaptive Mesh Refinement Visualization

**Notes:**
bis 12:30

## Level-dependent Transfer Functions

**Problem case: A fine level is completely enclosed within a coarse level**
**The coarse level can hide interesting regions of the fine level**
**Coarse level necessary to provide „context“ (orientation aid) for fine level**
**Cannot completely discard coarse level**
**Scale opacity and/or color saturation of coarse level**

- Current State of the Art in Adaptive Mesh Refinement Visualization

## No Transfer Function Scaling

**AMR 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

## Opacity Scaling

**AMR 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

## Opacity and Saturation Scaling

**AMR 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

## Texture-based AMR Volume Rendering

**[K****ähler & Hege, 2001 / 2002]**
**Resample to node centered**
**Subdivide in homogenous resolution regions (kD-tree)**
**Minimize number of blocks using information about AMR grid placement algorithm**
**Texture/Slicing-based volume rendering**
**Optimized texture packing**
**Adapt slice spacing & correct opacity**

- Current State of the Art in Adaptive Mesh Refinement Visualization

**Notes:**
Optimization: Bounding box & decompose outer region
Minimum slice distance, block slice distance = integer multiple of minimum slice distance, cull blocks intersected by to few slices at minimum slice distance
Grid = patch

## Rendering the First Star of the Universe

**[K****ähler et al., 2002]: Application to astrophysical data set**
**Texture-based volume renderer, Virtual Director, CAVE**
**Aired on Discovery Channel**

- Current State of the Art in Adaptive Mesh Refinement Visualization

**Notes:**
 The root grid with 64 x 64 x 64 cells was refined by 5, 500 grids on 27 levels of resolution resolving down to the region of the newly formed proto-star. An average frame rate of 0.3 fps was achieved. 

## Splatting-based Volume Rendering of AMR Data

**[Park et al., 2002]**
**kD-tree- and Octree-based domain subdivision**
**Specify isovalue range and transfer function**
**Rendering using hierarchical splatting**

- Current State of the Art in Adaptive Mesh Refinement Visualization

**Notes:**
IEEE Vis Case Study,
Not very detailed

## Direct Volume Rendering of AMR Data

**[Kreylos et al., 2002]**
**Homogenization using kD-tree**
**Distributed rendering using texture-based slicing**
**Cost-range decomposition**

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Framework for Parallel AMR Rendering

**Efficient reimplementation of cell projection**
**Sort cells [Williams, Max & Stein 1998]**
**Subdivision in object space with kD-tree**
**Subdivision of first hierarchy level**
**Uniform: Blocks of approximately equal size **
**Weighted: Blocks of  similar computational effort**
**Subdivision in blocks of constant resolution**
**Unweighted**
**Weighted**

- Current State of the Art in Adaptive Mesh Refinement Visualization

**Notes:**
12:30
Vereinfachende Annahmen:
	- Konst. Interpolation
     - Parallelprojektion

## Subdivision Strategies – Subdivision of the First Hierarchy Level

**Uniform**

**Weighted**

**X = Viewpoint; Color = Assigned processor**

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Subdivision Strategies – Homogenization

**Subdivision Strategies – Homogenization**

**Unweighted**

**Weighted**

**X = Viewpoint; Color = Assigned processor**

- Current State of the Art in Adaptive Mesh Refinement Visualization

**Notes:**
NOTE: Say colors represent different processor (I.e. caption on slide) X = viewpoint

## Timing Results

**Uniform subdivision**

**Weighted subdivision of first hierarchy level**

**Homogeneous subdivision**

**Weighted homogeneous subdivision**

- Current State of the Art in Adaptive Mesh Refinement Visualization

**Notes:**
bis 15:00

## Homogenization most efficient way to render AMR hierarchies
Computationally efficient
Use of standard methods
Use of kD-tree currently standard way of describing subdivision

Reasonable estimate of computational costs for rendering grid parts possible

**Computationally efficient**
**Use of standard methods**
**Use of kD-tree currently standard way of describing subdivision**
**Reasonable estimate of computational costs for rendering grid parts possible**

**Observations**

- Current State of the Art in Adaptive Mesh Refinement Visualization

## GPU-Assisted Raycasting of AMR Data

**[K****ähler et al., 2006]**
**Use raycasting instead of texture slicing**
**Higher quality (improved precision, avoid varying sample distances)**
**Sophisticated light model with wavelength dependent absorption**

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Visualization of Time-varying AMR Data

**Feature-tracking**
**[Chen et al., 2003] **
**Isosurface visualization**
**Track connected components through time and AMR levels**
**Remote visualization of time-dependent AMR data**
**[K****ähler et al., 2005]**
**Interpolation scheme for “in-betweening” of hierarchy levels evolving at different simulation rates**
**Access remote simulation over network**

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Specialized Tools for AMR Data

**ChomboVis**
**LBNL Applied Numerical Algorithms Group**
**Slicing and *****spreadsheets***
**Isosurfaces (w/ cracks)**
**Streamline computation (unpublished)**
**AMR Vis**
**LBNL Center for Computational Sciences and Engineering**
**Shear-warp volume rendering (re-sampling)**
**Slicing and *****spreadsheets***
**Streamlines**

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Spreadsheets

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Visualization Tools with AMR Support

**ParaView**
**Support for reading AMR data sets (e.g., VTM)**
**Slicing, Isosurfaces (with cracks)**
**Volume rendering in development (commercial version)**
**Amira**
**Some AMR support in internal collaboration version**
**Mainly volume rendering**
**VisIt**
**Support for reading AMR data sets (e.g., Enzo, Boxlib, Chombo)**
**Wide range of visualizations including volume rendering, slices, isosurfaces (currently w/ cracks)**

- Current State of the Art in Adaptive Mesh Refinement Visualization

## VisIt

**Richly featured visualization and analysis tool for large data sets**
**Data-parallel client server model, distribution on per patch-basis**
**Use of meta-data / contracts to reduce amount of processed data**
**Built for 5 use cases:**
**Data exploration**
**Visual debugging**
**Quantitative analysis**
**Presentation graphics**
**Comparative analysis **

- [Argon bubble subjected to shock
- Jeff Greenbough, LLNL]

- [Logarithm of gas/dust density in Enzo star/galaxy
-  simulation, Tom Abel & Matthew Turk, Kavli Institute]

- Current State of the Art in Adaptive Mesh Refinement Visualization

**Notes:**
The featured plot is a Volume plot of the logarithm of gas/dust density in an Enzo star and galaxy simulation. Regions of high density are white while less dense regions are more blue and also more transparent.The data used to make this image were provided by Tom Abel Ph.D. and Matthew Turk of the Kavli Institute for Particle Astrophysics and Cosmology.
This is a picture of an argon bubble being subjected to a shock.  The simulation was run by Jeff Greenough of LLNL using the Boxlib framework.  The image was made by me.The material boundaries are in blue (for 3/4).  Rings of high vorticity are shown in red (for 1/4).  And velocity magnitude is colored on the cross-section.

## VisIt and AMR Data

**Supported as “first-class” data type**
**Handled via “ghost-cells”: Coarse cells that are refined are marked “ghost” in the lower level**
**Isocontouring via resampling, cracks possible at level boundaries**
**Work on rectilinear grids and skip ghost cells or “remove” results produced in ghost cells later on**
**AMR capabilities currently under rapid development (planned as ChomboVis replacement this FY)**
**http://www.llnl.gov/visit **

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Acknowledgements

**Members of the NERSC Visualization Group, the Applied Numerical Algorithms Group (ANAG) and the Center for Computational Sciences and Engineering (CCSE) at LBNL**
**Members of the VisIt Development Team**
**Members of IDAV Visualization Group (UC Davis)**
**AG Graphische Datenverarbeitung und Computergeometrie**
**Members of ZIB and AEI**
**Department of Energy (LBNL)**
**National Science Foundation**
**Office of Naval Research**
**Army Research Office **
**NASA Ames Research Center**
**North Atlantic Treaty Organization **
**ALSTOM Schilling Robotics, Chevron, General Atomics, Silicon Graphics, and ST Microelectronics, Inc.**
**Stiftung für Innovation des Landes Rheinland-Pfalz**

- Current State of the Art in Adaptive Mesh Refinement Visualization

## Questions?