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Productivity Corner: A Close-Up Look at Feature Modeling

14 Mar, 2005 By: James Dyer Cadalyst

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This MicroStation features helps you easily create, modify and view feature-based solids models

In this month's Productivity Corner column we'll focus on an introduction to MicroStation V8's Feature Modeling capabilities.

MicroStation's Feature Modeling extension provides a powerful set of tools for 3D solids modeling. Solids models created using the Feature Modeling tools are fully editable, either using the parameters defined during creation, or graphically using Element handles while selected. When you add a feature to a SmartSolid, MicroStation will automatically convert the SmartSolid to a feature solid. However, only those features that were placed with the Feature Modeling tools contain the intelligence of feature solids and can be dynamically edited.

When you're working with the Feature Modeling tools, each item you create is known as a feature solid. Each feature solid is stored in a feature tree, along with the parameters defined during creation.

You can easily develop complex solids by adding, subtracting or merging two or more existing solids. To perform these operations, use the modeling operation tools from the Boolean Features toolbox (figure 1).

Working Area and Feature Modeling
When working with feature-based solids models, the Solids setting in the Working Areas section of the Advanced Unit Settings determines the largest single feature-based solids model that can be created in a model. You control Working Area Solid settings by accessing the Settings / Design File, Working Units category function.

MicroStation's local solids Working Area system provides a flexible environment.

• For SmartSolids, the Solids Working Areas setting specifies the area in the model in which solids can be constructed (centered on 0,0,0). All SmartSolids should be constructed within this working area.
• For feature-based solids models, the Solids Working Area is a local area for each solid. You can construct as many solids as you like, anywhere within the models, as long as each solid does not exceed the Solids Working Areas dimension.

Feature Modeling Toolboxes
Tools for creating, manipulating and viewing feature-based solids models are located in three toolboxes: Feature Modeling, Feature Modeling Primary, and Feature Modeling View Control (figure 2).

Feature Modeling Viewing Tools
The Feature Modeling tools include a toolbox specifically for controlling the viewing your 3D models. When these tools are used in association with a single open view, they let you quickly rotate the view to one of the standard view orientations. Additionally, you can quickly toggle the display of construction elements and toggle QuickVision display. If you have more than one view open, a data point is required to select the view to which the viewing tool is to be applied.

The toolbox incorporates standard displays tools for rotating a view to a Top, Front, Right or Isometric view, plus tools to toggle construction elements and QuickVision display. Additional tools that are available to be displayed in the toolbox are for rotating a view to a Bottom, Back, Left or Right-Isometric view. Finally, you can also use the right-click menu in the toolbox to select which tools you want displayed.

Creating Feature-Based Solids Models
Working with MicroStation's Feature Modeling tools allows you to create feature-based solids models incorporating various features in a very simple workflow:

1. Create the underlying feature solid(s)
2. Add features to the solid

When creating feature-based solids models, you begin with the development of your base solid. Once defined, you create additional features to which you perform modeling operations to add, subtract or union those features to the base solid (figure 3). The base solid may be a solid formed from a union of other solids, a Primitive Feature Solid (cube, sphere, cone, and so forth), a solid created by adding thickness to a surface or from extruding a profile.

Modifying Feature-Based Solids
Solids models created with the Feature Modeling tools are referred to as feature-based solids models. Feature-based solids models give you much more creation and manipulation flexibility, so you can incorporate design changes. You can easily modify feature-based solids models using the parameters defined during creation or by modify them interactively, similar to 2D elements.

Parametric Modification of Features
Feature-based solids models retain those parameters used during creation. This condition applies to both the base feature solid as well as features applied to it. The Modify Parametric Solid or Feature tool in the Modify Feature toolbox allows you quickly edit the solids model and/or features by modifying their individual parameters.

Modifying One or More Blends of a Group
If you have performed several modeling operations in a single step, you can modify them in a single operation. Alternatively, you can choose to change the radius for selected blends of the group.

Interactively Modifying Features
If you are modifying a feature interactively, by selecting the feature, the feature parameters associated with the feature update automatically. However, you still can use the parametric settings to modify the feature afterward, if required.

To modify interactively, simply use the Element Selection function to select a given feature with a data point. When you want to modify or move features, or use Ctrl data point when you want to scale a solid and all its features.

As you select the feature, MicroStation will automatically display the feature at the identification point, the centroid of the feature and at the modifying points for the feature.

Features Toolbox
Tools contained within the Features toolbox are used to add features to a solids model. You can create complex designs by starting with a base solid and adding the features required to refine your design. Feature solid tools typically have many options.

Cut Feature tool. Used to place a cut in a solid. With this tool, there is a Thickness setting.

Sweep Edge Feature tool. Used to construct a cut along an edge of a solid. The Sweep Edge Feature tool, allows you to define a cutting profile and an edge, or a group of edges, to use as a reference path.

Boss and Protrusion Feature tools. Used to construct a circular protrusion on a solid. You can add a circular boss or use a profile to add a protrusion.

Rib Feature tool. Used this to construct a rib between two faces of a solid. Tool settings allow you to choose how the rib is constructed.

• Normal Axis: Will set the direction of the normal to the rib's surface. Options are Points, or Edge/Face Normal. Whereby, Points allow you define the rib's normal by data points, while Edge/Face Normal will define the normal relative to the edge of face on which the rib is placed.
• Thickness: Will set the rib's thickness (must be greater than zero).
• Draft Angle: Allows you set a taper, from the root of the rib.
• Top and Base Blend Radii: Allows you to define blends at the base and/or the top of the rib.

Of course, after you have placed the rib, you have the option of using the Modify Parametric Solid or Feature tool to edit its values.

Thin Shell feature. Used to hollow out a solid a solids model with walls of a constant or varied thickness. Tool settings allow you to set:

• Shell Thickness: Default thickness for walls of the solid. Positive values add material to the outside of the original solid, whereby negative values remove material from inside the original solid.
• Face Thickness: Allows you to define values for one or more walls that differ from the Shell Thickness. Entering a Wall Thickness of zero removes the face entirely.

Modeling Methods
As there are many approaches to design challenges, a particular modeling operation can be accomplished in a number of ways. One thing to consider when modeling is how different features will react if you need to modify them in the future.

MicroStation's Feature Modeling allows you to easily create, modify and view feature-based solids models. And, when you incorporate the advanced design visualization tools into your presentation, MicroStation is a very cool place to express your creativity. We will explore more of the concepts and power related to designing 3D Surface models with MicroStation in the future.

Until next time -- enjoy MicroStation!

Cadalyst's MicroStation tips included in "Productivity Corner" are compiled by James Dyer and were tested using MicroStation V8 2004 Edition. Cadalyst welcomes MicroStation tips: E-mail them to james.dyer@bentley.com. By submitting a tip or code, you grant Cadalyst magazine the right to print and distribute your tip or code in print, digitally and by other means. Cadalyst magazine and the authors retain the rights to the tip or code, which are not to be downloaded or copied for commercial use.