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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.
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.
Offsetting Entities in a 3D Sketch
You can offset specific points in a 3D sketch to help you trace the shape of an existing object. This feature is useful in situation where you want to maintain the curvature of an object while offsetting the curve a fixed distance away from the original surface.

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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.
    - 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.
      - Helix Sketch Panel
        The following table summarizes the properties that are available for a helix sketch.
      - Equation Based Curve Panel
        The following table summarizes the properties that are available for an equation-based curve sketch. To define a curve using an equation, you enter the entire equation directly in the panel.
      - 3D Sketch Entity
        Sketches are comprised of sketch entities. The following table describes the 3D sketch entities that are available in 3D-CAD.
      - 3D Sketch Creation Controls
        When creating a point or a line in a 3D sketch, there are additional controls available to help you create and place these sketch entities in 3D space.
      - Offsetting Entities in a 3D Sketch
        You can offset specific points in a 3D sketch to help you trace the shape of an existing object. This feature is useful in situation where you want to maintain the curvature of an object while offsetting the curve a fixed distance away from the original surface.
  - 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.

Offsetting Entities in a 3D Sketch

You can offset specific points in a 3D sketch to help you trace the shape of an existing object. This feature is useful in situation where you want to maintain the curvature of an object while offsetting the curve a fixed distance away from the original surface.

In the following example, you want to draw a 3D spline that follows the curve of the trunk on a car. The goal is to create a rear wing that closely matches the shape of the trunk.

To offset points from a reference geometry:

Make sure that the geometry that you want to reference is visible in the graphics window.
Create a 3D sketch.
If required, adjust the grid spacing in the scene.
If some bodies are overlapping, or are in close proximity, it may be difficult to select the points. You can hide the surrounding surfaces to make it easier to select the points.
One method to achieve this is to select the relevant faces on the geometry, right-click a selection and choose Show Only.

The selected faces are the only ones remaining visible in the graphics window.
Adjust the selection filter to only select vertices.
Select the points that you want to offset.
Hold down the <Ctrl> key to select multiple vertices.
While holding down the <Ctrl> key, right-click one of the selected vertices and choose Convert to 3D Entities.
Create the offset points:
1. In the 3D Sketch panel, under the Create group box, click (Create Point).
2. In the Create Point group box, select Offset From Point.
3. In the graphics window, select one of the points that you converted to a 3D entity.
  The point that is used as the reference is highlighted in green in the graphics window.
  
  Enter the displacement values in the X, Y, and Z fields and press <Enter>.
4. Click Apply.
5. Repeat these steps to offset the other reference points.
Click (Create Spline), and in the graphics window, click the offset points in order to define the shape of the spline.

The end-result is a 3D spline that accurately follows the shape of the trunk on the car, offset by a set distance. You can subsequently use this 3D curve as the guide curve in a loft feature, or as the path in a sweep feature, and create a rear wing for the car.