The Dynamic Constraints feature of Impact offers a next generation parametric design solution, aimed at improving the integrity and reusability of designs.
The following article offers an overview of the new Dynamic Constraints features, as well as where to find further resources to help you get started.
Introduction to Dynamic Constraints
Although Impact, like many other CAD systems, has long since provided tools to design with accuracy, including smart snapping cursors and the ability to reference and lock to existing entities when drafting and editing, after the geometry was placed, none of those rules were remembered.
Designs created this way could then be freely edited (even accidentally). Resizing any designs either meant offsetting or stretching the existing geometry with the use of additional edit tools, or perhaps going back to build up a resizeable model with the use of the more traditional parametric dimensions engine.
By allowing designers to create Dynamic Constraints, they are able to define the rules and relationships that control how their geometry behaves, meaning they can be sure that their design choices are maintained as they (or others) continue to edit or resize their drawing.
Types of Dynamic Constraints
Impact supports many types of constraints to create incredibly powerful and flexible drawings, which fall into the following categories:
- Distance constraints can be used to control the length or radius of entities, and can be either fixed or associated with a variable or even a calculated expression
- Angular constraints offer control of the angle between two or more entities, or between an entity and a virtual horizontal axis.
- Lock constraints offer a quick and easy way to fix entities without the need for specifying angles or relying on other geometry. For example, it's possible to lock a line horizontally or vertically, or even to force two or more points to stay in perfect alignment.
- Geometric constraints are used to control the position of points, lines, curves, and other entity types. The most common and perhaps most powerful is the Coincident Constraint, which keeps entities and points connected together, but other common examples include the Parallel and Perpendicular constraints, each provided to build a strong yet flexible design.
- Dimensional constraints control the distances between entities, between points and combinations of the two. Again, these can be either fixed or associated with a variable or even a calculated expression.
- Equals constraints are a mix between Geometric and Dimensional constraints. They can be used to quickly create a matching relationship between two or more entities, without the need for additional variables or expressions. For example, making two lines the same length, two arcs the same radius, two angles the same, or control the distance between different pairs of entities or points.
Example Dynamic Constraints and their associated Icons - 1. Fixed Length, 2. Coincident, 3. Vertical Lock
Designing with Constraints
With Dynamic Constraints, ANY design can be quickly become parametrically resizeable: whether it's an entirely new design being drawn from scratch; a historical design; or an imported drawing.
Many of the existing Draw and Edit tools used for geometry construction in Impact have been updated to allow them to automatically create constraints during use (when the Constraint Manager is active).
For example, the Draw > Line Horizontal tool can automatically add a Horizontal constraint, to avoid adding it manually, and where a Line Length is specified (vs interactive placement), a parametric Driving Dimension can be created too.
Example - Horizontal constraint and Driving Dimension
Similarly, use of the existing Trim and Transform tools can automatically infer and add constraints when editing existing geometry. In the below example, filleting a corner between two existing entities has automatically added Tangent constraints between both sides of the fillet arc and the neighbouring connected lines, as well as maintaining the existing Coincident constraints to keep the entities connected together.
Example - Trim Fillet creating Tangent Constraints automatically
Constraint Tools
For adding constraints to and between existing geometry entities, Impact features a rich selection of new tools, which are especially useful for working with existing or imported designs you wish to make resizeable.
The list of available Dynamic Constraint Tools, as they appear in the Edit Tools menu and the default Dynamic Constraints Tools toolbar, is covered here.
This includes tools to add and delete each of the available constraint types, as well as tools to toggle the visibility of constraints and their related dimension entities.
Hints and Tips
Pre-selected Entities
Many of the Add Constraint... tools will behave differently according to any pre-selected entities. This is intentional and can be very powerful, allowing you to use a wide range of existing selection tools to identify the entities you wish to add constraints to.
For example, when running the Add Parallel Constraint tool with no entities selected, it expects you to pick line entities in turn to make parallel, whilst offering a modifier key to select more than two. The tool will then keep running until cancelled. However, with a number of line entities already selected, a single click of the Add Parallel Constraint tool will quickly make all lines immediately parallel, and the tool will then be cancelled automatically.
The documentation for each Constraint tool specifies the tool's behaviour with Pre-selected Entities, as well as the influence of modifier keys to override and enhance their default behaviour.
Adding Constraints to Existing Geometry
If working with existing non-resizeable geometry and wish to introduce constraints, it is recommended that you first apply geometric constraints to determine the shape of a design and create relationships between the entities and their end points. Then proceed to apply dimensional constraints to determine the size of objects in a design.
Enabling Constraint Manager with a Drawing Template
Whilst it's possible to toggle the Constraint Manager on/off at any time, it may be preferable to create or update a drawing template with the Constraint Manager enabled. This way, designers can conveniently choose whether they will automatically start creating and editing geometry with Constraints enabled or not.
Standards
Standards are simply resizable designs that are commnly configured with additional features to offer previews, allow for material selection, and typically offer options for controlling geometric features.
Much like Impact's existing dimension-based parametric models, it's possible to turn designs built with Dynamic Constraints into custom Standards that appear in the Impact Standard Library, which will then automatically resize when ran.
Please contact your Impact reseller for more details of reference and training material on this advanced topic.
Related Dynamic Constraints Tools
In addition to the updated Draw and Edit tools, and the newly introduced Add Constraint... tools, please review the following related topics:
Dynamic Constraints Toolbox
To offer further controls, feedback, and analysis of the constraints within the active drawing, a new Dynamic Constraints toolbox has been introduced.
It's advisable to enable this toolbox so you have access to it whenever the Constraint Manager is active, since it describes the current status of the model, including: indicating which further constraints are available to add; reporting any model errors; as well as indicating if any entities are Underdefined - i.e. too much freedom of movement to maintain the model integrity when resizing.
Dynamic Constraints Toolbox showing model status with Constraint Manager active
Dynamic Constraints Tools Toolbar
Impact v13 introduces a convenient new Dynamic Constraints Tools toolbar. This standard toolbar brings together the various Add Constraint... tools, as well as Visibility controls for related features, and importantly, the Constraint Manager Active toggle.
Dynamic Constraints Entity Inspector Tab
The Entity Inspector shows details of selected entities, and allows for some editing of certain entity properties.
With the Constraints Manager active, and one or more entities selected, a new Dynamic Constraints tab is visible, which allows for the inspection and editing of any related constraints, including options to delete or remove entities from an existing constraint - i.e. splitting a line from a collection of parallel lines.
Training Courses
Those attending relevant training courses in the future can expect to cover the fundamentals of using the Dynamic Constraints tools as part of the draw and edit feature set. However, for those upgrading who wish to get the full benefit of the new toolset, upgrade training is also available and recommended. This is designed to help you get up to speed with this and other newly introduced features and apply best practises.
Please contact your local reseller / Impact training centre for further details of course availability, including web-based options.
For customers with an active Software Maintenance Contract (SMC), we have also provided some basic constraint tool overview videos that can be viewed and followed along with here: Online Dynamic Constraint Tool Videos
Licensing
The Dynamic Constraints features are made available on all Draw and Edit enabled Impact licence bundles from the release of Impact v13 onwards, subject to user privileges configured at a database level. See the Constraint Tools option in User Privileges.