Working with Features and the Feature Tree

Creating geometry in 3D-CAD involves working with features and the feature tree. This section describes how to roll the feature tree back, forward, and to the end.

This section also explains how to suppress and unsuppress features. Manipulating the feature tree using these tools changes the state of the features and allows you to control where new features are inserted in the feature tree. Different feature state icons appear next to the feature nodes when their state changes.

Note Right-clicking on a feature node presents a pop-up menu relevant to that particular feature. Some of the actions are common to most of the features, while others are more specific.

What are Features?

Simcenter STAR-CCM+ uses a feature-based modeling approach in its tools for building 3D-CAD models. In this approach, you construct the 3D-CAD model using a series of operations, or features, each of which represents a particular action.

For example, a sketch feature is added to the model when you construct points, lines and curves on a sketch plane. An extrude feature is added when you select an existing sketch feature and extrude it in a particular direction. The entire set of features that is used to construct a model is stored in the feature tree in the order that you created them. For a full list of the features available in 3D-CAD, see Feature Tree Node Reference.

What is the Feature Tree?

The feature tree of a 3D-CAD model is an ordered sequence of all the actions (or features) that are required to build the final model. The Features manager node acts as a parent to all feature nodes within the tree. A full list of these nodes is given in the feature tree node reference section.

The feature tree is dynamic—that is, editing an existing feature in the tree impacts the outcome of subsequent features. The result from one feature acts as the input for the next feature, so that the resulting model is the cumulative effect of applying all the features to the original canonical sketch planes.

The dynamic nature of the feature tree means that you manipulate it to achieve different forms of the final model. If you roll back the feature tree to a particular point, then only those features that appear before the roll point are executed in the CAD engine. When you add a feature to a rolled-back tree, it is inserted at the roll point, rather than at the end of the tree. Rolling the tree forward (either to a specific feature or to the end of the tree) results in all intermediate features being reactivated within the CAD engine. These items are discussed in more detail in the relevant sections.

You can also suppress features to deactivate them. Suppressed features are not removed from the tree, and can be unsuppressed to reinstate their contribution.

An icon () next to the Features Group folder indicates that the folder contains features that are in different states (a mix of Valid, Invalid, Suppressed, Needs attention, and Rolled-back states).

You can switch between the 3D-CAD feature tree and the simulation object tree without having to close 3D-CAD.

Initial State

In its initial state, the feature tree contains nodes for each of the three canonical sketch planes. Right-clicking on any of these three nodes provides actions to create a sketch on the sketch plane, or to create a further sketch plane that is based on the initial canonical sketch plane.

Feature Interactive Sizing

For some features, 3D-CAD provides interactive sizing or positioning controls in the 3D-CAD View scene while you define the feature. The form of control depends on the feature you are adding, but generally you can see either arrows or a triad. The triad is associated with features that reposition or transform entities.

For example, to move a body, click and hold one of the three direction arrows on the triad. While holding the mouse button, you can move the selected entity along any of the three axes. To rapidly change the value of the position, in the 3D-CAD View scene, click and drag one of the arrows while pressing one of the shortcut keys listed below:
  • <Ctrl> increments values by 0.05
  • <Shift> increments values by 0.10
  • <Shift> + <Ctrl> increments values by 0.25.
For angular widgets:
  • <Ctrl> rounds angles up to the nearest degree
  • <Shift> increments angles by 5 degrees
  • <Shift> + <Ctrl> increments angles by 10 degrees