HiVis

Synopsis

AVS/Express modules for the visualization of octrees and sparse grids and the simplified and efficient integration of hierarchical adaptive data structures.

This project is classified as a special project by the IAC. Therefore we cannot offer the same level of support for this project as we do for other projects.

Objective

Encapsulate scientific data that is hold by hierarchical adaptive datastructures (e.g. Octree, Sparse Grids, ...) for the visualization. This is provided by a specification of rectilinear tiled grids (in short: adaptive grid) as a generalized version of uniform grids.

Description

In AVS/Express the Adaptive Grid is integrated as a new grid type. It provides following modules:

HiVis_Read_Octree: Read an octree and represent it as an adaptive grid.
HiVis_Read_SparseGrid: Read a sparse grid and represent it as an adaptive grid.
Field_To_HiVis: Convert an AVS/Express uniform grid to an adaptive grid representation. Data is unchanged.
HiVis_To_Field: Convert an adaptive grid to an AVS/Express uniform grid. Node data is interpolated.
AG_Octree: Convert an adaptive grid to an octree representation. Grid must have data in cells. Note: The octree aproximates an adaptive grid and is itself represented as an adaptive grid. This matter should be understood correctly. E.g. the conversion from an AVS/Express uniform grid to an octree can be obtained with the modules Field_To_HiVis and AG_Octree.
AG_SparseGrid: Convert an adaptive grid to an sparsegrid representation.
AG_Orthoslice: Orthoslice an n-dimensional adaptive grid (i.e. reduce by one dimension).
AG_Cell2Node: Convert celldata to nodedata.
HiVis_Bounds: Draw grid bounds (no data map as yet).
HiVis_Iso: Generate isosurface. Grid must have data in nodes.
HiVis_Streamlines: Generate Streamlines. Grid must have data in nodes.
HiVis_Render_Sparsegrid: Visualize the nodes of the sparsegrid datastructure.
HiVis_Render_Cells: Visualize the adaptive grid cell structure

The implementation is far from being complete. The integration of hierarchical adaptive datastructures into the visualization is an ongoing research topic. This package illustrates the choice of an abstract interface to unify different types of hierarchical adaptive datastructures for their visualization. But it does not take advantage of all aspects of the hierarchical adaptive data structures in the visualization. However here are some ideas for productive usage:

Visualize the structure of an octree or a sparsegrid using HiVis_Render_Cells
Integrate new hierarchic adaptive datastructures by inheriting from the adaptive grid base class (C++-class visAdaptiveGrid).
Interpolate a uniform grid with an octree or a sparsegrid, for example to illustrate image compression.

Known Bugs

After loading examples, that use the modules Generate_Octree or Generate_SparseGrid you have to manually update the modules by selecting different parameters like 'Max tree level' or epsilon values.

Documentation

Author

Peter Breitling ~ breitling@comagic.com

Modifications

Tobias Schiebeck,
International AVS Centre

Contact

International AVS Centre
Manchester Visualization Centre
Manchester Computing
University of Manchester
Oxford Road
Manchester
United Kingdom
M13 9PL