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NOTICE: This version of the NSF Unidata web site (archive.unidata.ucar.edu) is no longer being updated.
Current content can be found at unidata.ucar.edu.
To learn about what's going on, see About the Archive Site.
Dear colleague,
We thought that you or someone you know might be interested in getting
an early preview of what is coming in Version 4.0 of NCAR Graphics. We
are looking for some sites that would be willing to beta test the
software and give us some feedback on what they like and what they
don't. If we hear a common theme from beta testers on some aspect of
the software, it is not too late for us to make some changes before we
release it this summer.
If you are interested, please complete the questionnaire at the end of
this message and return it to us. We may not be able to select all
sites that respond, but we want to thank everyone in advance who
returns the questionnaire to ngbeta@xxxxxxxxxxxxx by March 27, 1995.
We have scheduled beta testing to run from early April to mid May. A
description of the software precedes the questionnaire.
NOTE: Two aspects of the Version 4.0 software will not be available to
4.0 beta testers: the prototype Graphical User Interface (GUI) and
direct output to PostScript files from the new interfaces. Direct
PostScript output from the traditional interface *is* available.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
New directions for NCAR Graphics
--------------------------------
NCAR Graphics Version 4.0 is the first step toward a scientific
visualization product that will be called NCAR Interactive. The
following overview describes Versions 4.0 and 4.1. The GUI that
completes the NCAR Interactive product will be provided only as an
unsupported prototype at 4.0; the supported GUI will be released with
Version 4.1.
The NCAR Interactive product will offer a fully integrated scientific
visualization environment. This environment will provide a means of
reading and writing data, a means of manipulating that data, and a
means of visually analyzing the data interactively. It will be
straightforward to use, efficient, and user-extensible. Furthermore,
this environment will support users with a wide range of skill levels:
from users with extensive programming and technical skills to novice
users who are learning to use NCAR Graphics for the first time and
have a low to moderate level of programming expertise.
Integrating interactive data access and manipulation with the visual
analysis techniques of NCAR Graphics provides many benefits to current
and future users of NCAR Graphics. In many cases, users will no longer
need to write custom data-reading code as a prerequisite for producing
graphics because the new data import functionality supports a variety
of data formats and file types. The process of tailoring a data plot
for a publication is simplified and accelerated.
Users will be able to develop customized plot specifications that can
be saved and re-used. New users will have many ways in which they can
learn NCAR Graphics by using a GUI, an ASCII scripting language, the
new C or FORTRAN programmatic interface, or the traditional C and
FORTRAN interface. Users who develop applications with NCAR Graphics
will be aided by the new API (Application Programming Interface) that
is consistent across utilities and designed to support many
interactive demands.
Three new interfaces
--------------------
The three major components of the NCAR Interactive system are:
o HLUs (High Level Utilities), a self-consistent toolkit programming
interface library
o NCL (NCAR Command Language), a text-based data manipulation and
graph specification language interpreter
o GUI (Graphical User Interface), a "point-and-click" graphical user
interface
These new interfaces all produce the same result: a user-specified
display of data.
HLU interface
-------------
The HLU library is built on top of the existing NCAR Graphics code.
The HLUs are a new interface to the traditional NCAR Graphics
utilities (now called the LLUs--Low Level Utilities). The HLUs manage
a great deal of the underlying low-level implementation details for
the programmer. The HLUs give users the ability to change features of
the output quickly and easily. The toolkit has entry points from both
FORTRAN, C and through the NCAR Command Language (NCL).
If you are familiar with X Windows, the following should indicate how
the NCAR Graphics High Level Utility (HLU) objects work. The HLUs are
implemented along the lines of the X Window System widget model. Many
aspects do not conform to this model, but the main concepts are valid.
The HLU model supports the demands of an interactive environment in
which different plots are created and displayed at different times
with different data and configurations. The HLU model encapsulates the
set of functions that draw a given type of plot with the set of data
needed to configure it. Multiple instances of each type of plot can
be created, destroyed, drawn and reconfigured without affecting any of
the other instances, in the same fashion as X Window System widgets.
If you are familiar with Object Oriented Programming (OOP), the HLU
model also supports derived classes of objects (inheritance) and
mixing of separate classes to form new classes (multiple inheritance).
This ability to mix separate classes allows one utility, like TickMark
or Title, to serve other utilities, like XyPlot or Contour. After you
learn how to configure TickMark objects, you will know how to
configure tick marks and grids in XyPlot and Contour plots. The OOP
principles of classes, objects, and parent-child relationships in the
instance hierarchy are also helpful in understanding the HLU model.
An HLU plot object can maintain its own unique data transformation and
its ability to map screen positions into data coordinates and vice
versa. Each object knows how much area it uses on the screen and can
report its bounding box coordinates. When objects change size, they
automatically and proportionally scale text, dash patterns, tick
marks, grids, and markers. All of these features support interactive
environments.
The Version 4.0 HLU library contains these utilities:
XyPlot draws curves and symbols on plots that contain grids, tick
marks, titles, and legends provided by other HLUs.
Contour draws and fills contours with or without maps on plots that
contain label bars, grids, tick marks, titles, and legends provided by
other HLUs.
MapPlot generates maps in any one of the ten standard NCAR Graphics
map transformations.
TickMark draws tick marks and grids for XyPlot and Contour plots; it
uses five transformation styles: log, linear, irregular, geographic,
and time.
LabelBar creates and fills label bars with patterns or colors for
Contour plots.
Legend displays symbols and lines with text to create legends for
XyPlot objects.
Title positions and draws titles for plots of other HLUs.
TextItem positions and draws text for plots of other HLUs.
Workstation directs output to various devices: an NCAR Computer
Graphics Metafile (NCGM), an X Windows display, or a PostScript file
(PostScript output from HLUs and NCL will not be available for the 4.0
beta test).
These HLUs will be added at the 4.1 release:
Histogram will create filled bars on plots that may contain grids and
tick marks provided by the TickMark HLU.
StreamLine will create streamlines with or without maps on plots that
contain features from other HLUs.
Vector will create vectors with and without maps on plots that contain
features from other HLUs.
3D will create simulated three-dimensional projections (surfaces and
iso- surfaces) on plots that contain features from other HLUs.
NCL interface
-------------
The heart of NCAR Interactive is the data manipulation and graph
specification language called the NCAR Command Language (NCL). NCL
provides easy, intuitive, and consistent access to datasets and allows
users to explore and process their data prior to visualization. Since
datasets often come in a variety of data formats, grid sizes, grid
resolutions, and units, very different datasets often need to be
combined, compared, and used at the same time. Prior to 4.0, NCAR
Graphics users had to develop specialized code to read individual
datasets and transform them into a form that was compatible with other
datasets being used and with the NCAR Graphics function interfaces. In
Version 4.0, NCL provides the functionality to import a variety of
data formats automatically. In many cases, this eliminates the need
for programmers to write data-import code.
NCL allows different datasets, in different storage formats, to be
imported into one uniform and consistent data manipulation
environment. The primary data format and data model used internally by
NCL is the netCDF data format and model. NCL places no restrictions or
conventions on the organization of input netCDF files. NCL has been
designed to allow for its extension to support other data formats. In
Version 4.0, NCL will support netCDF, HDF, and GRIB formats; data in
native machine binary and ASCII can be imported using special data
import functions.
NCL is a complete programming language that provides flexibility and
configurability. In NCL, the primary data type is the data file
record. A data file record stores one or more variables, dimension
information, coordinate variable information, and attribute
information as one NCL variable. NCL users can read a binary file,
then assign dimension names, variable names, attributes, and
coordinate variables to it using NCL language constructs; users can
then write the resulting file record to any of the currently supported
formats--including netCDF--without having to learn the API for any of
the data formats.
NCL is built on top of the HLUs--it allows users to create and
manipulate any HLU graphical object.
NCL's function set contains built-in data processing and mathematical
functions, and users can extend it to provide custom data processing
techniques and custom data ingestion.
In addition to functioning as a command line interpreter, NCL has an
API for submitting NCL scripts from within an application. This API
provides GUI writers a uniform way to access data and manipulate and
visualize plots from within their application using NCL scripts. This
simplifies the implementation of application-specific GUIs by reducing
the amount of time developers must spend on the visualization code and
the data access code.
Graphical User Interface
------------------------
NOTE: An officially supported GUI will not be available until Version
4.1, and the prototype GUI will not be available for 4.0 beta testing.
The NCAR Interactive GUI will be built on top of NCL, which is built
on top of the HLUs. The GUI will therefore provide access to NCL data
input and manipulation as well as the HLU visualization specification.
The GUI will simplify many user tasks by providing a "point-and-click"
interface for selecting data, creating plots, adding data to a plot,
modifying plots, and positioning plots within the output frame.
Further, the GUI will allow users to "probe" data visualizations by
attaching NCL scripts that perform some analytical function to various
key and mouse clicks, making true data interaction possible.
The GUI will also provide editors for color maps, fill patterns, line
styles, area masking, map projection specification, animations, as
well as a general resource editor.
New LLU functionality
---------------------
At Version 4.0, the LLU library will contain these new utilities:
Dashpack draws curves using dashed-line patterns that may include gap-
portion specifiers, solid-portion specifiers, and label-string
specifiers. Dashpack replaces and unifies the old "Dash" family of
NCAR Graphics routines: Dashline, Dashchar, Dashsmth, and Dashsupr.
Polypack allows users to manipulate polygons in various ways.
Wmap provides the graphics to produce daily weather maps, plot station
model data including wind barbs, and draw icons to indicate daily
weather.
A direct PostScript driver: PostScript output is producible directly
from the NCAR GKS package by way of opening any one of several
PostScript workstation types. Workstation types exist for producing
color or monochrome output, portrait or landscape orientations, and
regular PostScript, EPS (Encapsulated PostScript), or EPSI
(Encapsulated PostScript Interchange format) files.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Beta Tester Questionnaire
-------------------------
Please respond via e-mail to ngbeta@xxxxxxxxxxxxx no later than
March 27, 1995.
Your name:
Address:
Phone:
E-mail:
Job title:
Scientific discipline:
NCAR Graphics site license number:
(If you're not sure of this number, please call 303-497-1201.)
Please answer all questions
---------------------------
1. Please describe your job duties with respect to visualization and
data manipulation requirements.
2. How long have you been using NCAR Graphics? Do you mostly develop
your own NG applications or use NG programs generated by others? What
NG utilities (Autograph, Conpack, Ezmap, Labelbar, etc.) are you
currently using? What kind of applications do you use NG for?
3. Do you use any other visualization tools? If so, please list them,
your level of familiarity with them, and your uses of them.
4. Data manipulation:
a. Describe types of data visualized routinely, their geometry,
size, dimensionality, and source.
b. Describe how you most often choose to visualize your data (2D
contour plots, X-Y plots, plots overlaid onto a map, isosurfaces,
etc.).
c. List the data storage mediums and formats you use (including
binary, ASCII, and site-specific conventions).
5. Visualization needs:
a. Describe the types of visualizations you produce for publications.
b. Describe the types of visualizations you produce specifically for
data analysis, verification, validation and reduction.
c. Describe the types of visualizations you create that utilize 1D,
2D, 3D, and other higher multidimensional datasets.
d. Describe the types of multi-field visualizations (visualizations
combining multiple scalar fields and vectors).
e. Do you produce video animations or workstation animations? If so,
list the typical number of frames and their dimensions in your
animations.
6. Hardware available:
a. What types of printers and hardcopy (35mm slides, fiche, etc.) do
you use?
b. Please specify your UNIX workstation models, memory, disk
capacities, and operating systems (please include OS version,
which is available by typing "uname -a").
c. Other computing systems?
d. What system and OS would you use for the 4.0 beta test?
7. Is your site connected to the Internet?
8. Do you have and use a WWW browser (Mosaic, Netscape, lynx, etc.)
at your site? If so, which one(s) do you use?
9. Are you an application developer? If so, please describe the types of
applications you develop.
10. Are you a GUI developer? If so, please describe the types of GUIs
you develop.
11. Please indicate which NCAR Graphics interface, plotting utility,
data format and file type, and output type you will use in your
part of the 4.0 beta test:
Interfaces: NCL, HLU C, HLU Fortran, new LLUs
Utilities: XyPlot, Contour, MapPlot, TickMark, LabelBar, Legend,
TextItem, Title, Dashpack LLU, Polypack LLU, Wmap LLU, LLU
PostScript driver
Input data formats and file types: netCDF, HDF, GRIB, binary, ASCII
Output types: X Window display, NCGM
Animations? Yes, No
Thank you!
The NCAR Graphics Group thanks you for your interest in this new
product and your willingness to help us test it.
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