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Pre-Processing
Simcenter STAR-CCM+ solves physics problems on a computational mesh. To provide this mesh, you first define geometry using internal or external tools, and then create a mesh pipeline whose operations generate the mesh in repeatable steps.
Modeling Geometry
This part of the User Guide describes how to use 3D-CAD, the parametric solid modeler available within Simcenter STAR-CCM+. It also describes the features and tools available for further preparation of the geometry model and its surfaces.
Manipulating Parts
Simcenter STAR-CCM+ allows leaf-level parts to be manipulated in several different ways once they have been imported or created.
Retessellating a Part
The surfaces of a geometry part are represented using triangles which come from a process that is known as tessellation.

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Pre-Processing
Simcenter STAR-CCM+ solves physics problems on a computational mesh. To provide this mesh, you first define geometry using internal or external tools, and then create a mesh pipeline whose operations generate the mesh in repeatable steps.
- 3D-CAD
  3D-CAD is a feature-based parametric modeler within Simcenter STAR-CCM+ that allows you to build geometries from scratch. The geometries that you create with 3D-CAD are stored as 3D-CAD models, which you can then convert to geometry parts for integration with the meshing and simulation process.
- Modeling Geometry
  This part of the User Guide describes how to use 3D-CAD, the parametric solid modeler available within Simcenter STAR-CCM+. It also describes the features and tools available for further preparation of the geometry model and its surfaces.
  - Preparing the Geometry
    In general, a Simcenter STAR-CCM+ analysis requires one or more geometry parts from which you define the spatial construction of the regions. Simcenter STAR-CCM+ allows you to create geometry parts directly using the built-in 3D-CAD modeler, or import geometry from a wide range of source formats.
  - Importing Geometry
    One of the possible starting points for the meshing process is to import surface data.
  - Understanding Geometry Parts
    You can use the geometry parts manager node to control what parts are meshed and included in the simulation downstream.
  - Manipulating Parts
    Simcenter STAR-CCM+ allows leaf-level parts to be manipulated in several different ways once they have been imported or created.
    - Retessellating a Part
      The surfaces of a geometry part are represented using triangles which come from a process that is known as tessellation.
    - Transforming a Part
      Five different types of transformations are provided to transform parts.
    - Duplicating a Part
      You can duplicate a part in instances where only a half, quarter, or some fraction of a symmetrical or axis-symmetric model has been imported and the full geometry is desired instead.
    - Combining Parts
      Two or more parts can be combined to create a single mesh part.
    - Performing Boolean Operations
      This section describes the basic Boolean operations that can be performed on geometry parts.
    - Splitting Non-Contiguous Parts
      A non-contiguous mesh part (that is, a mesh part that has faces that are not connected to other faces in the part) can be split into its individual component parts if necessary.
    - Splitting a Part by Surface Topology
      The split by surface topology method can be used to split and combine parts that can be defined as distinct geometrical regions.
    - Replacing a Part
      You can replace a single CAD or mesh part at any time. Replacing a part lets you provide new geometrical input for the meshing pipeline without affecting any of the other data input required to generate a mesh.
    - Manipulating Part Surfaces
      Simcenter STAR-CCM+ allows leaf-level part surfaces to be manipulated in several different ways.
    - Deleting Empty Entities
      This option allows you to delete empty part surfaces and part curves. Empty part surfaces do not have face definitions in any of the descriptions in the simulation. Similarly, empty part curves do not have any feature edges in any of the descriptions in the simulation.
    - Manipulating Part Curves
      Simcenter STAR-CCM+ allows leaf-level part curves to be manipulated in several different ways.
    - Manipulating Part Points
      In addition to part surfaces and part curves, Simcenter STAR-CCM+ allows you to create part points. Part points are intended for specific applications that allow you to set quantities at point locations. For example, in solid stress simulations you can define loads and constraints at specific points.
    - Repairing Part Surfaces and Curves
      Repairs can be made to leaf-level parts at any time before surface initialization. They can be required to close a surface or fix some other non-valid entity that the translation process created.
    - Exporting Parts
      This section describes how to export the data that is contained in the geometry parts tree.
    - Getting the Face Count of a Part
      This section describes how to obtain the number of faces of a geometry part.
    - Editing Imported Parts in 3D CAD
      This section describes how to modify your imported geometry parts using 3D-CAD.
    - Part Operations Reference Page
      This section contains a list of available operations that appear when right-clicking a part.
  - Part Contacts
    Part contacts define the connection between two part surfaces. The meshers aim to generate a conformal mesh at the contact, which then becomes an interface in the physics region.
  - Repairing CAD Geometry
    The Geometry Repair tool provides diagnostic checks for assessing the validity of geometry and the means to repair the geometry automatically.
  - Displaying the Geometry
- The Surface Repair Tool
  The Surface Repair tool diagnoses errors in, and provides repair tools for, tessellated surfaces and part curves. The same tool allows you to reorganize discretized geometry by searching for face-based features and attributes then assigning the results to new or existing part surfaces or curves.
- Defining the Regions Layout
  An essential part of the process in setting up your simulation is to define the relationship between geometry parts and regions, boundaries, and interfaces.
- Meshing
  A mesh is a discretized representation of a geometric domain. This domain can include real-world geometry, its content, and its surrounding environment.

Retessellating a Part

The surfaces of a geometry part are represented using triangles which come from a process that is known as tessellation.

For 3D-CAD, imported CAD, and shape part types:

The triangle density that is used to tessellate a surface can be modified using the Re-tessellate... option on the right-click menu for the part.

Selecting this option opens the Tessellation options dialog. In addition to providing control over the tessellation density, the dialog also provides control over the marking of CAD edges as features edges. These options behave in an identical manner to the options that are provided on the Surface Import Options dialog. See the sections on Tessellation Density and Mark Feature Edges for details.

It is possible to see the triangles that are used to represent the surfaces by choosing to display the mesh in a geometry scene for which the Geometry representation is active.