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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.
Sketches in 3D-CAD
3D-CAD supports two types of sketch—2D sketches that are created on a planar surface and 3D sketches that are built from points located anywhere in geometric space. You can use both types of sketch in 3D geometry operations such as extrude, revolve, or sweep.
Constraining a Sketch
Constraints are used to impose geometric limitations on sketch entities as well as to control their position on the sketch plane.
Applying Constraints that Reference Other Sketches or Existing Geometries
You can select an edge from another sketch or geometry when creating a constraint in the active sketch.

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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.
  - 3D-CAD Environment
    The 3D-CAD environment provides you with a feature tree from which you can activate all steps for creating and modifying geometry, and a 3D-CAD View scene in which you interact with the geometry. Many of the same feature actions are available for selection in the 3D-CAD View scene.
  - Sketches in 3D-CAD
    3D-CAD supports two types of sketch—2D sketches that are created on a planar surface and 3D sketches that are built from points located anywhere in geometric space. You can use both types of sketch in 3D geometry operations such as extrude, revolve, or sweep.
    - Creating a Sketch
    - Dimensioning Sketches
      Dimensions are used to control sizes, distances, and angles in a sketch.
    - Constraining a Sketch
      Constraints are used to impose geometric limitations on sketch entities as well as to control their position on the sketch plane.
      - Constraint Types
      - Applying Constraints that Reference Other Sketches or Existing Geometries
        You can select an edge from another sketch or geometry when creating a constraint in the active sketch.
      - Reviewing Applied Constraints
      - Removing Constraints
    - Creating Sketch Fillets
      The Sketch Fillet option rounds off the corner that is formed between two lines on a sketch.
    - Creating Sketch Chamfers
      A sketch chamfer is a feature that makes a straight cut across the corner that is formed between two lines on a sketch.
    - Splines
      A spline is a smooth curve that is composed from a series of points (called spline points).
    - Projecting Entities to the Active Sketch
      You can project sketch entities from other sketches onto the active sketch.
    - Creating a Sketch in 3D
      Use 3D sketching to create sketches whose entities are constructed from points and lines located anywhere in 3D space. These 3D sketches can then be used to build or modify complex three-dimensional shapes.
  - 3D-CAD Geometry Modeling
    Bodies represent the individual objects that make up the 3D-CAD model. Imported CAD geometry appears as bodies in 3D-CAD, and you can also create your own bodies directly using 3D-CAD features.
  - Freeform Surface Modeling
    Freeform surface modeling is a modeling technique in 3D-CAD that allows you to deform existing surfaces for desired shapes.
  - Importing and Exporting Geometry
  - Working with 3D-CAD Models
  - Geometry Repair and Preparation
    Simcenter STAR-CCM+ provides a suite of tools in 3D-CAD that helps you to prepare your CAD geometry so that it is suitable for meshing. CAD that is designed for manufacture can have gaps or inaccuracies that cause problems when trying to generate a watertight mesh.
  - Design Parameters
    Design parameters allow Simcenter STAR-CCM+ to update geometry designs during design exploration studies. Although you define them within the 3D-CAD environment, they are exposed outside 3D-CAD for manual or automatic update.
- 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.
- 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.

Applying Constraints that Reference Other Sketches or Existing Geometries

You can select an edge from another sketch or geometry when creating a constraint in the active sketch.

The selected edge is projected onto the active sketch and is used to constrain the target entity in the active sketch. If the plane of the active sketch intersects the plane of the reference sketch, you can use the pierce constraint. See Pierce Constraint. This constraint is only available when selecting a point from the active sketch and an edge from the reference sketch, and ensures that the two sketch entities are coincident.

An example demonstrating how the projection works is shown below.

This feature gives you the ability to align sketch entities with one or more existing sketches. The same is also true for reference geometries, where the selected edge on the reference geometry is projected onto the active sketch. You can only use edges from a reference sketch/geometry to constrain an active sketch. You cannot use vertices from the reference sketch/geometry. When you modify a reference entity, the projection of that entity on the constrained sketch is also modified. This action can change the constrained sketch. If you delete a reference entity, the constraint that is based on that projection is also deleted. Using a similar method, you can pierce another sketch on a different plane, ensuring that the active sketch and the reference sketch are coincident.

In the following example, the gray geometry is used to constrain the active sketch (shown in blue).

To constrain the active sketch using a reference geometry:

Select the edge that you want to use as a reference from the reference geometry. This edge highlights in purple.
While holding down the <Ctrl> key, right-click the desired entity on the active sketch and select the required constraint from the right-click menu. In this case, the line that is on a diagonal must be parallel to the selected edge of the reference geometry, so Apply Parallel Constraint is selected.

The diagonal edge from the reference geometry is projected to the active sketch and the constraint operation is carried out.

Note	The projection does not appear on the active sketch. This operation is internal.

A symbol denoting the type of constraint is placed on the constrained sketch entity.

The two diagonal lines are now parallel to each other.