Chapter 11: Block References and Attributes

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Chapter 11 Block References and Attributes
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After completing this Chapter, you will be able
to use the followingfeatures

• Create and insert block references in a drawing
• Converting blocks into individual objects
• Multiple Inserts of Block References
• Define attributes, edit attributes, and control
  the display of attributes
• Redefining a Block and Attributes
• Block Attribute Manager
• Use the DIVIDE and MEASURE commands
• Dynamic Blocks
• Three Steps to create a dynamic block
• Block Editor Make a Block Dynamic

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Why create a Block?
The BLOCK command enables a designer to create an
object from one or more objects, save it under a
user-specified name, and later it can be inserted
into the drawing. When block
references are inserted in the drawing they can
be scaled up or down in both or either of the X
and Y axes and can be rotated as they are
inserted in the drawing.The block reference
acts as a single unit when operated on by certain
modify commands. Block reference can also be
dragged and dropped from one drawing to anther
through DesignCenter.
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Examples of common uses of blocks in various
disciplines
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Creating Block Definition
BLOCK command allows to create block references.
Objects that are on layer 0 when the
block is created will assume the color, linetype,
and lineweight of the layer on which the block
reference is inserted. Objects on any layer
other than 0 when included in the block
definition will retain the characteristics of
that layer, even when the block reference is
inserted on a different layer.
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Invoke the BLOCK command from
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Block Definition dialog box
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If the given name is the same as an existing
block in the current drawing, AutoCAD displays a
warning.
To redefine the block, choose Yes. The block with
that same name is then redefined. Once the
drawing is regenerated, any insertion of this
block reference on the drawing redefines to the
new block definition with this name. Choose No
in the Warning dialog box to cancel the block
definition.
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Inserting Block References
INSERT command insert previously defined blocks
into the current drawing. If there is no block
definition with the specified name in the current
drawing, AutoCAD searches the drives and folders
on the path for a drawing of that name and
inserts it instead.
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Insert dialog box
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Nested Blocks
Block references that contain other blocks are
known as nested blocks. Using blocks within
blocks can simplify the organization of a complex
block definition. With nested blocks, you can
build a single block out of several components.
There is no limitation to the depth of nesting.
You may not, however, use the name of any of the
nested blocks as the name of the block being
defined.
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Explode Command
The EXPLODE command causes block references,
hatch patterns, and associative dimensioning to
be turned into the separate objects from which
they were created. It also causes polylines
polyarcs and multilines to separate into
individual simple line and arc objects.
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Multiple Inserts of Block References
The MINSERT (multiple insert) command is used to
insert block references in a rectangular array.
The block reference group cannot be exploded.
This command works similar to the rectangular
ARRAY command.
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Base command
The BASE command allows to establish a base
insertion point for the whole drawing similar to
specifying a base insertion point when using the
BLOCK command. The newly established base
point will be used when the drawing is inserted
by way of the INSERT command. The default base
point is the origin (0,0,0).
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Attributes
Attributes are special text objects that can be
included in a block definition Attributes can
be used for automatic annotation during insertion
of a block reference. Attributes have two
primary purposes Allows annotation during
insertion of the block reference to which the
attributes are attached. Allows to extract
data from each inserted block reference and
saved in a file in a form that database-handling
programs can use.
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If an attribute is to be used only to store
information, specify whether or not it will be
visible when attribute is defined. If the
attribute is used as a note, label, or callout,
consider the effect of scaling (whether equal or
unequal X/Y factors) and rotation on the text
that will be displayed. The scaling factor(s)
on the attribute will be the same as on the block
reference. Attribute text that is defined as
horizontal in a block will be displayed
vertically when that block reference is inserted
with a 90-degree angle of rotation.
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Components associated with attributes TAG is
the identifier of the attribute definition and is
displayed where this attribute definition is
located, depicting text size, style, and angle of
rotation. The tag cannot contain spaces. Tags
appear in the block definition only, not after
the block reference is inserted. VALUE of an
attribute is the actual string of text that
appears (if the visibility mode is set to ON)
when the block reference (of which it is a part)
is inserted. Whether visible or not, the value is
tied directly to the attribute, which, in turn,
associates it with the block reference. It is
this value that is written to the database file.
PROMPT is what you see when inserting a block
reference with an attribute whose value is not
constant.
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Four primary commands are available to manage
Attributes ATTDEF Command defines the
attributes that is included in the block
definition. ATTDISP Command controls the
visibility of the attributes. EATTEDIT Command
provides various options to edit attributes
without exploding the block reference. EATTEXT
Command extract the data from the drawing and
saves to a file in a form that database-handling
programs can use.
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ATTDEF command
ATTDEF Command defines the attributes that is
included in the block definition.
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Blocks with attributes inserted in a manner
similar to that for inserting regular block
references. If there are any non-constant
attributes, AutoCAD prompts for the value. To
suppress the prompts for attribute values set the
system variable ATTREQ to 0 (zero). The values
will either blank or set to the default values if
they exist. Use EATTEDIT command to establish or
change values.
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ATTDISP command
ATTDISP Command controls the visibility of the
attributes.
ON selection makes all attributes visible OFF
selection makes all attributes invisible.
Normal selection displays the attributes the way
it was defined.
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EATTEDIT command
EATTEDIT Command provides various options to edit
attributes without exploding the block reference.

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Edit Attributes dialog box with Attribute tab
selection
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Edit Attributes dialog box with Text options tab
selection
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Edit Attributes dialog box with Properties tab
selection
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EATTEXT command
EATTEXT Command extract the data from the drawing
and saves to a file in a form that
database-handling programs can use.
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The Data Extraction - Begin (Page 1 of 8) page
lets you extract block attribute data to a table
in the current drawing or to an external file.
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The Data Extraction Define Data Source(Page 2
of 8) page lets you select a drawing file from
which to extract information from Block
Attributes or lets you specify blocks in the
current drawing.
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The Data Extraction Select Objects (Page 3 of
8) page allows you to select which blocks and
attributes in the selected blocks will have their
data extracted to the specified table and/or file.
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The Data Extraction Select Properties (Page 4
of 8) page lets you select the properties for
data extraction.
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The Data Extraction Refine Data(Page 5 of 8)
page lets you refine the selected data.
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The Data Extraction Choose Output (Page 6 of 8)
page lets you choose the output format.
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The Data Extraction Table Style (Page 7 of 8)
page lets you choose the table style.
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The Data Extraction Finish page(Page 8 of 8)
lets you complete the data extraction.
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Redefining a Block and Attributes
The ATTREDEF command allows to redefine a block
reference and updates associated attributes.
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Block Attribute Manager
The BATTMAN command provides a means of managing
Blocks that contain Attributes. Allows to edit
attribute definitions in blocks, change the order
in which Attributes are prompted for attribute
values when inserting a block, and remove
attributes from blocks.
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Dividing Objects
The DIVIDE command allows to divide an object
into equal-length segments, placing markers at
the dividing points. AutoCAD provides option to
place invisible points or block reference as
markers. Objects eligible for application of
the DIVIDE command are the line, arc, circle,
ellipse, spline, and polyline.
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Measure command
The MEASURE command allows to divide an object
into specified-length segments, placing markers
at the measured points. AutoCAD provides
option to place invisible points or block
reference as markers. Objects eligible for
application of the MEASURE command are the line,
arc, circle, ellipse, spline, and polyline.
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Dynamic Blocks
AutoCAD allows to manipulate/modify individual
objects or groups of objects within a dynamic
block reference. You can manipulate the geometry
in a dynamic block reference through custom grips
or custom properties. This allows you to adjust
the block in-place as necessary rather than
searching for another block to insert or having
to redefine the existing one.
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Three Steps to create a dynamic block
The first step to create a dynamic block is to
create the geometry. This can be accomplished
either in the normal AutoCAD drawing area or in
the Block Editor drawing area. The second step
to create a dynamic block is to add a parameter.
Parameters are used to establish points,
distances, and angles on or near objects in the
block so that actions can be applied to those
objects, making that block dynamic. Parameters
also allow you to control visibility of objects
in the reference and make use of the properties
of the geometry in the reference. The third
step consists of adding an action, selecting
objects, and closing the Block Editor. Actions
are added to parameters and then associated with
selected objects in the block. These objects are
the selection set that will be affected by the
subsequent selecting of the appropriate grip in a
reference of the block and initiation of the
action.
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Using the Dynamics of a Dynamic Block
When a dynamic block is inserted and the
reference is selected for modification, the
geometry is highlighted and a grip will appear at
the insertion point of the block as it usually
does and a grip will also appear where the
parameter is defined. Select the grip to modify
the geometry. The Move Action grip appears when
the block reference is selected for modifying as
shown in the example
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Block Editor Make a Block Dynamic
The Block Editor is an authoring window dedicated
especially to creating and editing dynamic
blocks. Use the Block Editor to make a dynamic
block out of an existing non dynamic block, or
while creating a new block. Open the Block
Editor by selecting Open in block editor in the
Block Definition dialog box before choosing OK to
create a new block. Also possible to open the
Block Editor by double-clicking on an inserted
block reference on the screen.
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Block Editor
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Block Editor toolbar
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The parameter, in combination with the associated
action, determines the location and appearance
of the grips that appear when a reference of the
block is selected for modifying.