Chapter 11 Block References and Attributes After completing

Chapter 11: Block References and Attributes

After completing this Chapter, you will be able to use the following features: • 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 • DIVIDE and MEASURE commands • Dynamic Blocks • Three Steps to create a dynamic block • Block Editor – Make a Block Dynamic

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 Design. Center.

Examples of common uses of blocks in various disciplines

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.

Invoke the BLOCK command from:

Block Definition dialog box

If the given name is the same as an existing block in the current drawing, Auto. CAD 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.

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, Auto. CAD searches the drives and folders on the path for a drawing of that name and inserts it instead.

Insert dialog box

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.

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.

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. On-screen prompt minsert (ENTER)

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).

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.

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.

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.

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.

ATTDEF command ATTDEF Command defines the attributes that is included in the block definition.

Blocks with attributes inserted in a manner similar to that for inserting regular block references. If there any non-constant attributes, Auto. CAD 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.

ATTDISP command ATTDISP Command controls the visibility of the attributes. View menu Choose Display > Attribute Display On-screen prompt attdisp (ENTER) ON selection makes all attributes visible OFF selection makes all attributes invisible. Normal selection displays the attributes the way it was defined.

EATTEDIT command EATTEDIT Command provides various options to edit attributes without exploding the block reference.

Edit Attributes dialog box with Attribute tab selection

Edit Attributes dialog box with Text options tab selection

Edit Attributes dialog box with Properties tab selection

EATTEXT command EATTEXT Command extract the data from the drawing and saves to a file in a form that database-handling programs can use. Modify II toolbar Choose the Attribute Extract command Tools menu Choose Attribute Extraction… On-screen prompt eattext (ENTER)

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.

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.

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.

The Data Extraction – Select Properties (Page 4 of 8) page lets you select the properties for data extraction.

The Data Extraction – Refine Data(Page 5 of 8) page lets you refine the selected data.

The Data Extraction – Choose Output (Page 6 of 8) page lets you choose the output format.

The Data Extraction – Table Style (Page 7 of 8) page lets you choose the table style.

The Data Extraction – Finish page(Page 8 of 8) lets you complete the data extraction.

Redefining a Block and Attributes The ATTREDEF command allows to redefine a block reference and updates associated attributes. On-screen prompt attredef (ENTER)

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.

Dividing Command The DIVIDE command allows to divide an object into equallength segments, placing markers at the dividing points. Auto. CAD 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. Draw menu Choose Point > Divide On-screen prompt divide (ENTER)

Measure command The MEASURE command allows to divide an object into specified-length segments, placing markers at the measured points. Auto. CAD 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. Draw menu Choose Point > Measure On-screen prompt measure (ENTER)

Dynamic Blocks Auto. CAD 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.

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 Auto. CAD 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.

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:

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.

Block Editor

Block Editor toolbar

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.