User Features

User features are used to encapsulate a geometric or technological construct. In some cases, depending on the selected input, and especially in an automation context, the user feature may be in error, with no possibility to determine what's wrong with it.

This section gives information concerning the following topics:

This page discusses:

Designing a Robust User Feature
Using Conditional Geometry
Catching Errors

Designing a Robust User Feature

You can design a robust user feature.

First of all, it is recommended to make a prototype of your user feature in a power copy. The latter is much more flexible. This way your design can be made in several steps and you don't have to start again from scratch. At instantiation, it is also easier to handle possible troubles. You can get the most out of the visibility provided by the power copy features.
If the user feature embeds a sketch, this sketch has to be iso-constrained. Thus, when instantiating the user feature and making changes in its new context, you must avoid uncontrolled modifications of the sketch geometry that you wont be able to manage because the user feature is a "black box". For the same reason, make sure that your sketch is attached>, and for that, always use the creation of sketch With absolute axis definition. This way, you are sure that the sketch is at the right position.
If the user feature embeds contextual geometrical items like a draft or a fillet, it has to be resolved. It means that the base of their constructions has to be embedded too and must not be considered as an input of the user feature. For example a fillet on the edge of a pad depends on the geometry of the sketch of the pad. If this sketch is in input of the user feature and changes from square to round, the fillet inside the user feature is broken and the user feature in error.
Do not embed datum or geometrical elements with external links to other documents (Copy\Paste as result with link). Don't try to embed a Body into a user feature, it is impossible. Because a Body is a package which can be empty or can contain Knowledge features for example. Whereas a user feature is a geometrical feature. To make it compliant, you have to transform the Body into a geometrical feature with a Boolean operation like Assemble, Remove, Intersect. After this, you can select the Boolean operation when defining the user feature and the associated Body is automatically embedded.

Using Conditional Geometry

To evaluate the environment of the user feature (its inputs) and to make decisions, Engineering Rules Capture provides three main functions.

Some measures (distance, angle, area, length, center of gravity, ) that can be used to evaluate the inputs. For more information, see the Reference section of the Engineering Rules Capture User's Guide.
Some geometric parameters that can be valuated by other geometries. For more information, see the Reference section of the Engineering Rules Capture User's Guide.
If / then / else keywords allow you to choose how to validate those geometric parameters depending on the measure results.

Catching Errors

Usually, if an update error is raised inside a rule, the rule execution is stopped and the rule sends an evaluation error message.

The Do not catch evaluation errors option which is available by right-clicking the relation in the specification tree and selecting the Properties command enables you:

To create features in error
To know (through an error message) if a feature is in error and
To make changes (or not) in case of errors.

This capability can be used to perform a geometric computation (such as intersection) and to decide what to do if there is no result.

let x(Point)
x = intersect ('Geometrical Set.1\Line.1', "Geometrical Set.1\Line.2')
if (x.Error==true)
'Geometrical Set.1\Point.5' = point(0mm, 0mm, 0mm)
else
'Geometrical Set.1\Point.5' = x