Appendix C. Environment Variables and Command Line Options
C.1 Environment Variables
The environment variables described in this section can be set in your
login profile to customize Data Explorer.
Note also that these variables can be overridden on the command line
(see C.2 , "Command Line Options").
Path variables specify a directory or directories to be searched for
Directories are searched in the order of their appearance in the
variable, reading from left to right, with successive path names
separated by a colon (:).
Thus when a file appears in more than one directory, Data Explorer will choose
the first copy it finds (i.e., in the leftmost directory
containing a copy).
specifies directories to be searched for importable
If the data to be imported is in your current directory or one of the
specified directories, you do not need to enter the complete
path name in the Configuration dialog box for the
given just the file name, the Import module will search all of these
specifies directories to be searched
for include scripts.
Data Explorer uses include scripts in script mode.
It is not necessary to specify this variable in Edit mode.
See "File Inclusion" for more information.
specifies directories to be searched for macros when Data Explorer
If DXMACROS is not specified, you will have to load
macros individually (see 7.2 , "Creating and
specifies the directories to be searched for outboard modules.
Setting a Path Variable: Examples
Note the colon (:) separating successive path names.
- To set DXMACROS for both the Bourne (sh) and the Korn (ksh) shells:
- To set DXDATA for the Korn shell (ksh) only:
- To set DXDATA for the C shell (csh):
setenv DXDATA /usr/mydirectory/mydata:/usr/group/groupdata
Other Environment Variables
sets the level at which the change to using a private color map is made.
The allowed values are -1 and the range from 0 (zero) to 1 (one)
and represent the Euclidean distance in RGB color space,
normalized to 1 (one) for the maximum
The default value is 0.1.
If this variable is set to 1, a private color map will never be used;
conversely, if it is set to -1, a private color map will always
(See Display in IBM Visualization Data Explorer User's Reference.)
specifies the default set of arguments for Data Explorer start-up.
An option specified on the command line will override the corresponding
setting in the variable.
sets the number of digits in axes tick labels at which a switch to
scientific notation is made. The default is 7.
specifies a file name containing
string and RGB value pairs as an alternate for
The string name can be used by any Data Explorer tool where a color can be
specified by name (for example, Color).
The RGB value specifies the specific numeric value for the color.
enables ReadImage to create delayed color images if the image is a tiff
format image saved in a byte-with-colormap format or a GIF format.
This feature is enabled if this variable is set to any value.
Delayed colors use less memory.
specifies an executive to be run at start-up.
You should set this variable only for a customized version of Data Explorer.
If DXFLING is set to 1, then for hardware-rendered images, in rotation
mode and execute-on-change mode, if you drag the mouse across the image,
and release the mouse button outside the image, the object in the image
will begin to rotate, and will continue to rotate until you click inside
the image. The direction and speed of the mouse motion before release
will affect the rotation direction and rotation speed of the object in
sets the gamma correction for
images displayed to the screen by a
Display or Image tool.
On many display devices a given change in the digital brightness of the
image is not reflected in a corresponding change in screen
A gamma correction is a nonlinear adjustment of the pixel values to
compensate for this difference and produce a more accurate
representation on the screen.
By default (except for
8-bit windows on
the sgi architecture), the correction factor
(exponent) is 2 (two), on the assumption that the display
is not otherwise gamma corrected.
The DXGAMMA variable allows you to override this default.
In particular, if the display device is already gamma corrected, set
the variable to 1 (one).
(See Display in IBM Visualization Data Explorer User's Reference, and
README_sgi in /usr/lpp/dx.)
DXGAMMA_8BIT, DXGAMMA_12BIT, and DXGAMMA_24BIT
set the gamma correction for
images displayed to the screen in 8-, 12-,
or 24-bit windows by a Display or Image tool.
This variable overrides the value set by DXGAMMA.
specifies the machine name of the server on which the executive is to
The default is "localhost".
(See 9.3 , "Connecting to the Server" for
information on how to connect to the
To determine the host name, enter the command:
sets the gamma correction for hardware-rendered images displayed to the
screen by a Display or Image tool. On many display devices a given
change in the digital brightness of the image is not reflected in a
corresponding change in screen brightness. A gamma correction is a
non-linear adjustment of the pixel values to compensate for this
difference and produce a more accurate representation on the screen.
By default, the correction factor is 2, on the assumption that the
display is not otherwise gamma corrected. The DXHWGAMMA
variable allows you to override this default. In particular, if the
display device is already gamma corrected, set the variable to 1.
if both GL and OpenGL are supported, you can override the default
library (which is platform-specific; please see the appropriate README
file for your architecture in /usr/lpp/dx)
by using this environment variable. It should be set to either DXhwdd.o
(for GL) or DXhwddOGL.o (for OpenGL).
specifies the name of the .mdf file that contains
custom-added modules for customized versions of Data Explorer.
sets the amount of memory (in megabytes) that can be used by the
for faces, loops, and edges data, if set, allows loops other than the
enclosing loop for a face to be listed first. However, there is a
consequent decrease in performance if this environment variable is set.
if set to anything, disables framebuffer readbacks. Setting this environment variable will improve performance of interaction with hardware rendered images, especially for machines for which readback is slow. However, some of the interactions in the image window (such as zoom) will result in a black image while interaction is taking place. If you are not planning on using the Image tool, then it is strongly recommended that this environment variable be set. The default is that framebuffer readbacks are enabled.
sets the image type to either 24-bit color images or
floating-point-based 96-bit images (the default).
This affects the behavior of Render and ReadImage.
This variable can be set to either DXByte (24 bits) or DXFloat (96 bits).
Setting this variable to DXByte will result in images taking up less
sets the number of processors for Data Explorer SMP.
specifies the remote shell command to use when connecting to other systems (such as those when using distributed execution). The default is the the path to rsh.
prevents the remote "invoke dxexec" script from being written with a full carbon copy of the local environment (only DISPLAY is set).
specifies the top-level directory for all the files and
directories needed by Data Explorer.
The default is /usr/lpp/dx.
specifies whether or not shared memory should be used. The amount of
memory allocated by Data Explorer for its data and object management can be set
at runtime with the -memory command line option. At startup,
Data Explorer either allocates a shared memory segment or expands the existing
data segment to create this space.
SMP (multiprocessor) systems are required to use shared memory so each
processor can share a common data space. SGI systems also use shared
memory for space. IBM systems use shared memory if the size to be
allocated is larger than 256 MB. In all other cases Data Explorer extends the
existing data segment using the brk() system call.
Each architecture (SGI, IBM, HP, ...) has a different way of
configuring the maximum user data segment size, and a different way of
setting the limit on the maximum size of a single shared memory segment.
Consult your system administrator or system documentation if you have
problems getting Data Explorer to use the amount of memory which should be
available to you.
If you have problems using a large data segment, you can force Data Explorer to
use shared memory by setting the DXSHMEM environment variable
to any value other than -1. This will override the defaults and use
shared memory for space. Alternatively, you can force Data Explorer to extend
data segment (if allowed for the architecture) by setting
DXSHMEM to -1.
Note: Regardless of the setting of DXSHMEM, the aviion and
sun4 architectures always use the data segment.
Some architectures have a default configuration which limits the size of
shared memory segments (see the architecture specific README file in
/usr/lpp/dx), and the system configuration must be changed as
root to increase the maximum allowed size of a shared memory segment. If
the maximum is not reset or if it is already set to a different limit,
then you can use DXSHMEMSEGMAX to tell Data Explorer what the current
limit is in megabytes (e.g. 128 == 128 MB). Data Explorer will allocate
multiple shared memory segments if necessary to get the total amount of
space, but it must be able to allocate them at contiguous virtual memory
allows the user to specify the size of the send and recieve buffers for the socket connection between the UI and the exec. This value is clamped to the max allowed by the system. This can fix a problem where the executive and UI hang involving a deadlock situation in the socket communication. The value assigned to it is passed as the parameter to setsockopt for SOL_SNDBUF and SOL_RCVBUF. A typcial increased value may be 262144.
Specifies a file containing user interactors for use by the
SuperviseState and SuperviseWindow modules (see
SuperviseState and SuperviseWindow in IBM Visualization Data
Explorer User's Reference).
DX_WEB_BROWSERunder UNIX specifies the web browser to launch for viewing the HTML documentation. Under Windows and MacOS X setting this environment variable will launch the systems default web browser.