9.7 How to Use the ITEM Wizard
9.7.1 The ITEM Workflow
The Immersive Topology Environment for Meshing (ITEM) is a wizard-like environment that guides the user through the mesh generation process from geometry definition to export. ITEM was designed to provide a step-by-step set of tools to help new users generate a mesh with very little previous knowledge of the Cubit program. But ITEM is also flexible enough to accommodate advanced users who want to use a more iterative approach, or who just want to use ITEM for a specific tool or panel.
The main ITEM task page is shown below. To access this page, click on the "wizard hat" icon from the Power Tools window.
The main item tasks are shown both in the text window, and also along the sidebar. The icons in the sidebar are available from any of the ITEM panels. It is acceptable to jump to different tasks during the process, although beginning users may just want to follow the steps in order. To get to the main task page, click on the Task icon on the sidebar during any step in the process.
Many meshing tasks require an iterative approach to the mesh generation process. For your convenience, if you do click on one of the task buttons from a different panel, it will take you to the last visited panel in that section. For example, if you are on the mesh generation page, and you click on the prepare geometry section, it will take you to the last page you visited in the prepare geometry section.
There are two help links at the bottom of the main task page. The first link will open this document which describes the general ITEM process and how to use the panels. This page is only accessible from the main task page. The second link opens the main ITEM documentation which describes each process in the ITEM mesh generation process in detail. This document can be accessed from any of the ITEM panels.
To proceed through the ITEM panels you must either click on a task or click on the "Done" button at the bottom of each page. There is no "Back" button on the ITEM interface. But in most cases, clicking the "Done" button works like a "Back" button.
9.7.2 Using an ITEM Panel
The item panels are designed to be self-explanatory, with plenty of documentation on each page, and access to more help if needed. However, it does help to be generally familiar with the main types of panels.
220.127.116.11 Task panels that link to other ITEM panels
Some ITEM panels provide a list of tasks that link to other ITEM panels. Sometimes the tasks are designed to be completed in sequential or iterative fashion. In that case, you will be returned to the task page after selecting done on each sub-panel where you can select the next task. The Prepare Geometry panel is an example of this case. Each of the tasks with a warning flag should be completed. As you return to this panel, you may need to run the diagnostics again, and possibly even revisit previous task pages.
In other cases, the list of tasks is a presents a list of choices, from which you will only select one option. The Import Geometry Page shown below is such an example. It gives a list of different geometry import/creation options and you just select one of the alternatives.
18.104.22.168 Task Panels that Link to Control Panels
22.214.171.124 Set-up Panels
126.96.36.199 Diagnostic Panels
The most useful type of ITEM panel is the diagnostic panel. These panels each focus on a specific diagnostic such as invalid topology, small features, blend surfaces, overlapping surfaces, or meshability. Most of theses panels contain some or all of the following features.
Diagnostic Button - Clicking on this button will run a series of tests on the model.
Output Window - Displays the results of the diagnostics and lists entities with problems. Includes a right-click menu with visualization and other options.
Automatically Repair Button - Tries to solve the problems automatically.
Solution Window - Presents a list of specific solutions based on the entity you select in the output window. This window also contains several right-click context menu items for each solution, including a "More Information" button which will open the documentation to information about that specific task. Another useful feature of the solution window is that in most cases clicking on one of the solutions will preview that option in the graphics window.
Execute Button - Executes the solution selected.
Additional Options - Sometimes you won’t see your desired solution in the list. Additional solutions with brief descriptions are provided at the bottom of the panel. Clicking on these links will open the corresponding control panel.
More Information Link - Opens a page describing the diagnostics and solutions used for this panel.
9.7.3 Undo Button
The Undo button allows you to reverse the most recent command. To enable the Undo button, click on the "Enable Undo" option from the Edit menu. The undo button works by saving information about your model after each step. For large or complex models, this can be time consuming, so you may need to disable the undo feature. Additionally, not all commands are enabled for undo. Many of the graphics and meshing commands, and various default settings are not included. Within ITEM, many commands are bundled into a single button click. Clicking undo will attempt to reverse all of the executed commands. See the command line window for the results of the undo command.
9.7.4 Magic Mesh Button
This button, shown at the top of each ITEM panel, provides the user with the opportunity to use Cubit’s internal automation algorithms to generate a mesh. In addition to simply issuing a mesh command, it will attempt to execute the following steps.
Geometry Cleanup: Check for small or ill-defined geometry and automatically resolve it
Auto-scheme: Automatically set meshing schemes and select sources and targets for hex meshing
Decomposition: If hex meshing, attempt to decompose the volume to admit a sweep or mapped mesh
Force Sweeps: For almost-sweepable geometry, modify the linking surfaces to force a sweep
Imprint/Merge: For assemblies, imprint adjacent volumes and merge common surfaces
Overlap check: Check for any remaining overlapping volumes and attempt to resolve merge problems
Mesh sizing: For tetrahedral meshing, automatically define a sizing function based on geometry characteristics
Interval Matching: For hex meshing, coordinate the assignment of curve intervals.
Sweep grouping: Determine an appropriate order to mesh volumes to reduce dependencies
Mesh: Perform the mesh operation volume(s)
Mesh Quality: Check mesh quality and locally optimize if necessary
If for any reason, Cubit is unable to complete these steps without further user intervention, the process will stop and the user will directed to continue with the ITEM workflow. For simple geometries, executing the magic mesh button at this phase of the workflow may be all that is necessary to completely define a good quality mesh. For other more complex geometry, considerable user intervention may be required.
The magic mesh button may be executed at any time during the ITEM workflow by selecting the button at the top right corner of the ITEM panel. Once the user has visited the various panels of the ITEM interface to provide user intervention, the automatic execution of the appropriate operations will not longer be attempted.
9.7.5 Getting Help
There are several ways to get help from within the ITEM interface. Most of these have already been discussed, but they are listed here again for reference:
How to Use ITEM - This document which is available only from the main task page
Guide to Meshing in ITEM - A document which describes the ITEM workflow, and how to use the diagnostics on each page. This is accessible from each page using the More Information links.
Individual help topics for specific solutions - Opens the documentation to help for each specific solution topic. This is accessible from the right-click menu when a command is selected in the solutions window.
Documentation included on panels - Many of the panels contain brief descriptions and explanations to describe the features and tools on that panel.