Notes on Modular Visualization Environments

At the turn of the century, someone defined an inventor as a "person who makes an ingenious arrangement of wheels, levers and springs, and believes it civilization." Now, nearly a hundred years later, it could be said that an inventor is a person who concocts an ingenious arrangement of computer code and believes it intuitive. Since everyone's intuition has its off-days, this guide provides a few tips for using IRIS Explorer , a decidedly "ingenious arrangement."
--from the Iris Explorer User's Guide

Overview of MVEs

What are MVEs?

Modular visualization environments (MVEs) allow the user to create visualizations by selecting program modules from a library and specifying the flow of data between modules using a interactive graphical networking or mapping environment. Maps or networks may be saved for later recall.

General classes of modules include:

data readers
data filters
data mappers - map data into 2D or 3D geometry (or sound)
viewers - 2D and 3D
control structures
data writers

Common MVEs include:

apE - Ohio State - 1987
Application Visualization System (AVS) - Advanced Visual Systems - 1988
Iris Explorer - SGI/NAG (Numerical Algorithms Group)
Data Explorer - IBM
Khoros - Univ. New Mexico / Khoral Research

Why use MVEs?

Require no graphics expertise
Allow for rapid prototyping and interactive modifications
Promote code reuse
Extensible- allow new modules to be created
Reasonably powerful and complete for a broad range of problems
Often allow computations to be distributed across machines and even platforms (Extreme Group's PSE)
Can promote more appropriate visualization through comparison

Why not use MVEs?

Poor performance on large data sets
Not-so-easy "ease of use"
More restrictive than general programming
Platform and expense
Can promote poor visualizations (easy use often leads to high glitz factor)

Iris Explorer Overview &Demo

Explorer Sample Maps

Explorer Data Types

Parameter (scalar)
Lattice (array, including images)
Pyramid (irregular grid)
Geometry (Inventor-based)
Pick (user interaction with geometry)
(in addition, users can define their own types with a typing language)

Other Features of Explorer

Data Scribe utility for specifying lattice (array) file formats and creating reader/writer modules
Interactive interface widget editor (even works for pre-packaged modules)
Ability to collapse groups of modules into a single group module with a single control panel (buggy in 3.0?)
Scheme-like scripting language for controlling modules and wiring entire maps
Explorer Typing Language
Module Builder for creating new modules in C, C++, or Fortran
Incorporation of Other Software:
- 3D Graphics - Open Inventor --> VRML?
- 2D Images - SGI's ImageVision Library
- line graphs/graphics - GnuPlot
- video - ?
version 3.5 works with Windows NT

Example - Groundwater Model Visualization

Links to resources

General info on MVEs

Computer Graphics, May 1995 issue focuses on the past, present, and future of MVEs

Iris Explorer
- NAG's Iris Explorer Center (pretty weak)
- NAG's UK Iris Explorer Center (slow connection but much better content!)
AVS
IBM's Data Explorer
- IBM page
- Cornell Repository
Khoros