#!F-adobe-helvetica-medium-r-normal--18*
#!N 
#!CSeaGreen #!N  #!Rall192 Identifying Connections #!N #!EC #!N 
#!N In Data Explorer, we identify connections in the following way. 
List the sample point location vertices in any order: that list 
is called the "positions" as we discussed above. Consider each point 
in the positions list to have an ordinal number, starting at 
0 for the first point in the list (these ordinal numbers 
are not explicitly listed in a Data Explorer file). A connection 
is denoted by a "list of lists" of numbers in which 
each entry represents the ordinal values of the points that are 
to be connected, listed in the order they are to be 
connected. So for example, if the first point in the positions 
list is "0.0 0.0" and the second point is "1.0 0.0," 
we denote a  #!F-adobe-times-medium-i-normal--18*   line #!EF connection between these two points 
by "0 1," indicating that a line joins point 0 (first 
point in the positions list) to point 1 (the second point 
in the list). #!N #!N As mentioned above, a  #!F-adobe-times-medium-i-normal--18*   triangle 
#!EF connection must reference three positions and a  #!F-adobe-times-medium-i-normal--18*   quad #!EF 
references four positions. For complete examples of position and connection lists, 
see  #!Ldatmod,dxall197 h Understanding the Data Model  #!EL  . #!N #!N As a direct extension of this 
concept, when we define volumetric elements like  #!F-adobe-times-medium-i-normal--18*   cubes #!EF and 
 #!F-adobe-times-medium-i-normal--18*   tetrahedra #!EF , we can perform 3-dimensional interpolation and derive 
a reasonable data value for any point in a sample volume. 
The good news about all of this interpolation is that Data 
Explorer already knows how to do the necessary calculations. As a 
researcher, your job is to define your data space to Data 
Explorer--its positions, connections, and data-dependency--but you do not have to worry 
about the details of how the interpolation is actually performed. #!N 
#!N The connections list is optional if it makes no sense 
to connect your sample points; for example, if you are studying 
gas molecules, there may be no meaningful interconnecting lines between separate 
molecules. Nevertheless, you may wish to define "line" connections linking the 
atoms within each molecule, in order to visualize interatomic bonds or 
protein backbones; or you may define cubic volumetric elements in the 
space around the nucleus if you wish to visualize electronic potential 
fields, for instance. #!N #!N In any case, you must define 
a set of connections before you can perform interpolation operations between 
sampled data values. This is true both for position-dependent data and 
for connection-dependent data. Once again, positions are discrete points in space, 
and connections are logical paths between those points representing reasonable interpolation 
paths between the sampled data values. If you do not have 
connection information available, you can use the Connect or Regrid modules 
to create connections for scattered point data. #!N #!N If you 
work with regular grids, the "connections" can be defined in a 
simple way by Data Explorer regardless of the import format you 
are using. See  #!Ldatmod,dxall197 h Understanding the Data Model  #!EL  in this Guide and  #!Lqimd,dxall109 h Importing Data  #!EL  in IBM 
Visualization Data Explorer QuickStart Guide. #!N #!N If your work requires 
irregular grids, you will need to carefully read the section of 
this manual that describes the format of Data Explorer element types. 
You may need to write a filter program to convert the 
connection list output from your finite element program to the format 
required by Data Explorer before you can import and visualize data 
sampled on arbitrary structures. #!N #!N #!N  #!F-adobe-times-medium-i-normal--18*   Next Topic #!EF 
#!N #!N  #!Linvdat,dxall194 h Invalid Data  #!EL  #!N  #!F-adobe-times-medium-i-normal--18*   #!N 
