In this tutorial you will create a Tcl script that creates spline surfaces from the nodes of selected tria elements.

Tools

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The Tcl commands if, foreach, and incr will be used to add logic to the script.  The command hm_getentityvalue is used to extract information from HyperMesh entities, based on data names.

Data names are generic references to the information that physically define an entity in the HyperMesh environment.  An example of this is the x-, y-, and z-coordinates that define a node location in three-dimensional space.  The available data names for each can be found in the HyperMesh Reference Guide Data Names topic.

Data names are accessed using the hm_getentityvalue command.  This command uses the data names available for an entity to return the particular value of interest.  The command will return a value that is either a string or a numeric value, depending on the command syntax and the value stored in that particular data name field.  The basic syntax of the command is:

hm_getentityvalue entity_type id data_name flag

where entity_type is the requested entity type (elements, loads, nodes, etc…), id is the entity ID, the data_name is the data field name of interest, and flag is either 0 or 1 depending on whether the command should return a numeric value (0) or a string (1).

To retrieve the x-component of a force with ID 12, the following command can be used:

set force_x [hm_getentityvalue loads 12 "comp1" 0]

Note that to assign the value from the command to a variable, the command is placed within square brackets.

Exercise

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Create a Tcl script that creates spline surfaces from the nodes of selected tria elements.  This requires that the script read data from the element entities.  To create the spline surfaces, retrieve the 3-node IDs of the tria elements.

Step 1:  Define the process.

The script should automate the following process:

Step 2:  Determine the data names to use to extract the element type and node IDs.

The following table lists several relevant data names for tria elements:

Steps 3-14:  Create the Tcl script and add logic as necessary.

A Tcl script to perform this function might be similar to the following:

Step 3:  Open a text file and save the file as HM8070.tcl.

Step 4:  Allow the user to select the desired elements and then add those loads to a list

The *createmarkpanel command is used to allow the user to graphically select the elements from the HyperMesh interface and add them to the mark.  The command below adds the elements to mark 1.  Once the elements have been added to mark 1, the element ids are assigned to a list called elems_list, using the TCL command set.  Add the following 2 lines to the file HM8070.tcl:

 

*createmarkpanel elems 1 "Select tria elements to create surfaces";

set elems_list [hm_getmark elems 1];

Step 5:  Begin an if loop which checks to see if the variable elems_list has values.  If it does, proceed with the macro.

Before continuing with the macro, we should check to make sure that the variable elems_list has values in it.  This is done by using an if loop.  In the if loop below, we are checking that the variable elems_list is not empty.  Add the following line to the TCL file to initialize the if loop:

 

if {$elems_list != ""} {

 

Step 6:  Initialize a variable which counts the number of times the foreach loop is entered.

The variable success_count is initialized and set to 0.  This variable is used to count the number of times the foreach loop (defined in Step 7) is entered.  We will use this variable at the end of the script.   Add the following line to the TCL script:

set success_count 0;

 

Step 7:  Use a foreach loop to iterate through each element in the list elems_list and then set a variable config which stores the element configuration.  This is extracted using the hm_getentityvalue command and the appropriate data name.

Using a foreach loop, each element in the list elems_list will be iterated through.  Within the foreach loop, each load is referenced by elem_id and then the variable config is defined.  This variable is set to the result of the hm_getentityvalue which uses the element data name config to report the configuration of the element.  A tria element will have an element configuration of 103 while a quad element will have a configuration of 104.  Add the following 2 lines to the TCL file:

 

   foreach elem_id $elems_list {

       set config [hm_getentityvalue elems $elem_id "config" 0];

 

Step 8:  Begin an if loop which checks to see if the variable config has a value of 103.  If it does, proceed with the macro.

Using an if loop, the variable config is checked to see if it doesn’t have a value of 103.  A value of 103 means that the element configuration is a tria element.  If the value is not equal to 103, the continue statement is used to move outside of the foreach loop.  If the value is the config variable is 103, then the macro is continued.  Add the following lines to the TCL script:

      if {$config != 103} {

           continue;

       }

Step 9:  Set 3 variables which contain the node id of each of the nodes used to define the tria element.

Three variables are defined (node1, node2, and node3) which represent the 3 nodes that define the tria element.  These 3 nodes will be used to create the spline surface.  Using the hm_getentityvalue command and the element data names node1, node2, and node3 along with the pointer id, the node id is retrieved and assigned to the appropriate variable.  Add the following 3 lines to the TCL script:

       set node1 [hm_getentityvalue elems $elem_id "node1.id" 0];

       set node2 [hm_getentityvalue elems $elem_id "node2.id" 0];

       set node3 [hm_getentityvalue elems $elem_id "node3.id" 0];

 

Step 10:  Set the appropriate mode to create the surface.

Using the *surfacemode command, the surface mode can be set according to the following:

1 – mesh keep surface

2 – mesh delete surface

3 – mesh without surface

4 – surface only

In this example, we only want to create a surface, so mode 4 is used.  Add the following line to the TCL script:

 

       *surfacemode 4;

 

Step 11:  Create a node mark which contains the 3 nodes defined in Step 9 and then use the *splinesurface command to create a spline surface using the nodes in the mark.

Using the *createmark, mark 1 for nodes is created and it contains the 3 nodes defined in the variables node1, node2, and node3.

   

 *createmark nodes 1 $node1 $node2 $node3;

       *splinesurface nodes 1 0 1 1;

 

Step 12:  Increase the variable success_count which is used to count the number of times the foreach loop is entered.  Then, close the foreach loop.

Using the incr command, the variable success_count is increased.  Following this command, a } is used to close the foreach loop.  Add the following 2 lines to the TCL script:

       incr success_count;

   }

 

Step 13:  Clear the node and element marks, and then use the hm_usermessage command to report the number of spline surfaces created.

Using the command *clearmark, mark 1 for the nodes and elements is cleared.  Following these commands, the hm_usermessage command is used to report the number of spline surfaces created.  The variable success_count is used to do this.  Because this variable was increased each time the foreach loop was entered and the element configuration was 103, this variable kept a count of the number of spline surfaces that were created.  Add the following 3 lines to the TCL script:

   *clearmark nodes 1;

   *clearmark elems 1;

   hm_usermessage "$success_count splines created."

 

Step 14:  Add an else statement which compliments the if statement which checked to see if the elems_list variable was empty.  If it is empty, the else statement is executed.

The else statement compliments the if statement defined in Step 5 which checks to see if the elems_list variable is empty.  If it is empty the else statement is executed.  Inside the else statement, the hm_errormessage command is used to report to the user that no elements were selected.  Following the hm_errormessage command, the if statement is closed using a }.  Add the following 3 lines to the TCL script file:

} else {

   hm_errormessage "No elements selected";

}

 

Step 15:  Test the script.

source HM8070.tcl

It is often necessary to debug Tcl scripts using the Command Window.  This allows you to run the Tcl script and easily review error messages, as well as print out debug information.  Additional details can be found in the Creating Tcl Scripts and Running Tcl Scripts sections.

 

There are several important things to notice.

 

 

See Also:

HyperMesh Tutorials