Attributes Inspector
All About the Currently Selected Attribute (or Dimension or Face)
Every object in your document -- including the outermost group itself -- has attributes. Attributes are always numerical. The Attribute Inspector allows you to examine and alter the numerical value for any attribute you select.
Design Intuition provides a default set of attributes for every object you create -- for the position coordinates and dimensions of an object. These attributes also correspond to parts of an object. Dimension attributes correspond to the dimensions drawn in the document view. Position coordinate attributes correspond to faces of an object.
For example, draw an object. Now click on any of its dimensions, and then select the Attribute Inspector. You'll see that the attribute is fully described in the inspector. You can change the numerical value of any attribute and see the change reflected in the object. Be sure to specify measurement units whenever you change values.
The full potential of the Attribute Inspector becomes clear in object authoring mode, where you can create attributes of your own.
Name
The names of elements cannot be changed. However, if you add an attribute to an object (see Add Authored Attribute to..., below), the attribute is created nameless. Before another attribute can refer to it, you will need to supply a name. Design Intution allows you to include spaces and numbers in names, but doing so can lead to confusion later. We recommend avoiding doing so.
If you do change the name of an authored attribute, and it happens to be referenced in another attribute's expression, the latter's expression will be instantly updated to use the new name. This guarantees that, when you save your design, all the expressions will continue to be valid and operate correctly.
Add Authored Attribute to...
You can add attributes to any object or group. In Design Intuition, these are called Authored Attributes, because they have several distinctions: they can be named, deleted (see Authored Attribute, below), moved around (ditto), and optionally be unitless (plain numbers, rather than being a quantity of some measurement unit, see Measurement Units, below).
Before you can add any authored attributes to your design, you need to switch into Authoring Mode.
You can use them in cases where several objects have a value or an expression in common. For example, into many of the cabinets built available in the Library, an authored attribute named plywoodThickness was added, whose value is 3/4" and locked. Several pieces refer to this attribute in their expressions. This makes it easy to translate a cabinet into metric, for example.
Refers to Attributes in Object
When expressions refer to other attributes (most do), they typically are referring to the containing group's attribute. If you create an attribute in your object and want to refer to it (in the expression for another attribute), you will need to uncheck Refers to Attributes in Object in this other attribute so that Design Intuition will be able to find it and use it in this other attribute's expression.
Measurement Units
Occasionally you may want an attribute to simply be a number and not a measurement. For example, you may want an attribute to represent the number of shelves in your bookcase. To convert a measurement into a plain ordinary number, uncheck Measurement Units.
Value
The value of an attribute is computed from its expression, unless it is locked (see Locking the Value, below).
Locking the Value
Design Intuition allows you to prevent an attribute's value from being altered. By now, you may have noticed that you can resize objects and groups. By locking the value of an attribute, for example, the Width of one object, then any attempt to stretch or shrink the Width of that object will not affect it. You can lock an attribute's value by selecting the attribute and then clicking on the little padlock next to the word Value. This same padlock also appears in the table of values in the Object inspector and in the Details view, when the checkbox labeled show expressions is UNCHECKED (located both at the top of the Inspector window and at the top of the Details view).
For example, when constructing a cabinet from 3/4" plywood, you would set the Width (or Depth or Height) of the plywood to that value and then lock the value.
A CAVEAT About Locking Dimension Values
If you lock a dimension (Width, Depth or Height) of an object, you ought to alter the expression of the corresponding extent, such that it uses the origin and the dimension of the object, rather than the default expression (the corresponding extent of the containing group). If you don't, the 2D and 3D views will disagree in strange ways, and the object will react inconsistently to moving a resize knob, depending on which knob is being moved.
This operation requires two simple steps. First, check the checkbox labeled Refers to Attributes in Object. Second, replace the expression with the one below in the left-hand column, which corresponds to the name of the attribute, which appears in the right-hand column.
| extent | expression | |
|---|---|---|
| Right | = | Left + Width |
| Back | = | Front + Depth |
| Top | = | Bottom + Height |
This doesn't seem very intuitive!
I agree, and I feel badly about it, because I've worked pretty hard to make Design Intuition as intuitive as possible. This introduces some confusion into the idea of locking values. I have in mind a nice partial solution to this problem, coming up soon.
Expression
The expression of an attribute can be any of the following:
- a measurement
- a number (unitless)
- a reference to another attribute
- an expression involving any of the above (eg, Left + Width),
- operators can be: +, -, *, or /
- parentheses are allowed
- * and / are computed before + and - (think: normal high-school algebra)
Whew! Some aspects of Design Intuition (and particularly this one) are challenging, and technical descriptions can be such a headache to interpret. What this says is that attributes are very flexible, flexible enough to allow you to create the kinds of Smart Objects which are in the Library. Explanations and eamples of some of this flexibilty can be found in the following places:
Locking the Expression
Design Intuition allows you to prevent an attribute's expression from being altered. This becomes necessary in those rare cases when your expression contains a number that you don't want Design Intuition to touch. You can lock an attribute's expression by selecting the attribute and then clicking on the little padlock next to the word Expression. This same padlock also appears in the table of values in the Object inspector and in the Details view, when the checkbox labeled show expressions is CHECKED (located both at the top of the Inspector window and at the top of the Details view).
For example, you might subtract twice (multiply by 2) the thickness of plywood from the Width of your cabinet in the expression for the Width of a shelf. If you don't lock this expression, Design Intuition will alter the 2.
Authored Attributes area
Authored attributes can be deleted. They can also be promoted to the containing group. That said, Design Intuition offers a helping hand in several ways.
Design Intuition can detect for you whenever an attribute is being used. If you delete such an attribute, the other attribute (the one that is using it) will no longer function correctly. This is bad, especially since it can take a while to locate this other attribute (a very long while, if your design has lots of objects and groups in it).
So, if an attribute is being used, the delete button will be greyed out and an explanation will appear.
If you think it should not be in use, you can find out what attribute is using it by selecting one of the items in the Referring To This: popup menu (see What is the "Inspect Something Else" area). This will become the selected attribute and the attribute inspector will change all of its information, accordingly. Of particular use is the fully qualified names area, described below. Once all of these referring attributes no longer refer to the attribute you want to delete, Design Intuition will re-enable the Delete button.
Promoting an attribute means to remove it from its object and place it into the group which contains the object. This allows it to be used by other objects contained in this group. Design Intuition will make sure that the Details view and the Select Something Else area of the inspector are brought up to date.
Fully Qualified Names
Expressions are composed in a kind of shorthand. They contain references, by name only, to attributes in the group that contains the object whose attribute you are inspecting. Sometimes it can be useful to see the longhand version, to see what's really going on.
