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An Introduction to AutoCAD Dynamic Blocks: Making Callout Blocks
Jaiprakash Pandey posted on December 01, 2016 |

Dynamic blocks are intelligent AutoCAD blocks with custom properties that have multiple features along with the geometrical features of legacy blocks. Using a dynamic block, you can put the geometries of many blocks in a single block like a door block for many different door types. You can also add properties to the dynamic block to change its length, orientation, scale or angle.

In this article, I will explain the Dynamic Block feature of AutoCAD with a practical example that employs a callout block that is generally used to represent different views in a drawing or sheet set.

Making Geometry for Block

Make a circle with radius of 10 units and then start the polygon command by typing “POL” in the command line. Specify the number of sides as “4” for polygon and click at the center of the circle to designate it as the polygon's center. Select “circumscribed about circle” from the command line options and enter a radius of 10 units for circumscribed circle and press Enter. You will notice that a square will be formed around the existing circle.

Rotate the square to a 45-degree angle with respect to its geometric center, or rotate the center of the circle in such a way that one of the edges points upward. Make a horizontal line that connects the vertices of the square along the diameter of the circle as shown in Figure1.
Figure 1. Polygon and circle for a legacy block.

Trim the part of the square below the horizontal line and make a solid hatch in three triangular regions on the remaining portion of the geometry. Make sure you create separate hatches in the triangular region by selecting the “Create Separate Hatches” icon from the “Options” panel of the Hatch Creation tab. Now remove all the lines from the geometry, including the line making triangular hatch boundaries,and make another line connecting the circle on diametrically opposite quadrants in the horizontal direction as shown in Figure 2.

Figure 2. Final geometry for a block.

Converting Geometry into a Legacy Block

You have a simple geometry for the block and this geometry can be used to create the required dynamic block. To make the block “Type B”, press Enter: it will open the Block Definition window.Enter the name of the block in the “Name Field” and select the center of the circle as a pick point. Next, select all geometries from the drawing; then click on “Allow Exploding” and “Open” in the Block Editor window radio buttons and click on “OK.”

You will notice that the block will open in the Block Editor window and that all customizations such as adding attributes and dynamic block properties can be performed in this window.Start with adding attributes to the block.

To add attributes, click on the “Attribute Definition” icon on the “Action” parameters panel of the Block Editor tab (see Figure 3). An attribute definition window will pop up. Enter “VNUM” as the tag in the tag field and type “View Number” in the prompt field. Click on the field icon in the default field, and select “Sheet Set” from the Field Category drop-down menu. Select the “Sheet Set” placeholder from the “Field Names” panel and select “View Number” from the “Placeholder Type” panel and click “OK.” Select the appropriate text settings like “Justification”, “Text Style” and “Text Height” and then click on “OK” and place a tag on the upper half section of the block. Similarly, repeat the process to add the sheet number attribute in the lower half of the block.
Figure 3. Attribute Definition window.

So far you have made a simple legacy block and added simple attributes to it. Now it's time to add the properties of a dynamic block to this simple block. The block in this case is expected to show two different geometrical property changes according to section, detail and elevation view and rotation about the block's center. Start by adding the first set of properties that is changing the visibility of certain elements of the legacy block to make it suitable for the “Section,” “Detail” and “Elevation” callout blocks (see Figure 4).

At first, make sure the Block Authoring palette is visible in the Block Editor.If the palette is not visible, then click on the “Authoring Palettes” icon on the “Manage” panel. The geometry in the legacy block has three hatches: one on the top and another two on either side. You can turn off all of these hatches to create a detail callout. The “Elevation” callout can be made by turning off the visibility of blocks on either side of the geometry. For a section block, you need not make any change as it is represented by arrowheads on all of the three sides.
Figure 4. Three different types of callout blocks.

To toggle the visibility as mentioned above, select the “Visibility” parameter from the Parameters tab of the Block Authoring palettes and place this parameter close to the geometry. Now click on the “Visibility States” icon on the “Visibility” panel (see Figure 5) and rename the existing visibility state as “Section.” Add two more visibility states with the names “Detail” and “Elevation.” While adding the visibility states, make sure that the “leave visibility of existing objects unchanged in new state” radio button is turned on in the new Visibility States window.

Figure 5. Visibility States option on the Visibility panel.

Next, click on the drop-down menu on the “Visibility” panel and you will notice that all visibility states are listed on it. At this point, changing the visibility state will have no effect on the current block. To make these changes, select the “Elevation Visibility” state from the drop-down menu and click on the “Make Invisible” icon of the “Visibility” panel, or use its command equivalent,“BVHIDE.” Click on objects that you want to hide in the “Elevation Visibility” state.For this case, click on two arrowheads on the left and right side of the block, and then press “Enter.” You will notice that the selected objects will be hidden or grayed out depending upon the option selected in the “Visibility” mode.

Now change the visibility state to “Detail” from the drop-down menu and once again select “Make Invisible” from “Visibility” panel, or use the “BVHIDE” command. This time, click on all arrowheads and press “Enter” to hide them. Now you are all set with the visibility parameter and if you toggle visibility state from the “Visibility” panel, you will see three different types of blocks.

Now you also can add rotation parameters to the block. Toggle visibility of hidden elements in the block by clicking on the “Visibility Mode” icon of the Visibility palette. Select the “Rotation” parameter from the Parameters tab of the Block Authoring palette and click at the center of the circle. Click at a point outside the circle and press “Enter” to place the “Rotation” parameter. Now go to the Actions tab of the Block Authoring palette and select the “Rotate” option. Click at the “Angle 1” parameter (see Figure 6), select all the three shaded hatches, and press “Enter.” If required, turn on the visibility of the “Rotation” parameter in all visibility states of the block (i.e., in “Detail,” “Section” and “Elevation”).
Figure 6. Final dynamic block with Visibility and Angle parameters.

Testing the Final Dynamic Block

Now that your dynamic block is fully prepared, close the Block Editor and save all the changes. Delete the existing block from the drawing area and insert the “Callout Block” from the Insert window. You can also use the “INSERT” command to insert a block.

When your block is inserted, you will notice that it will have two grips: one for changing visibility state and another for changing its rotation angle. Click on the visibility grip and change it to “Detail” or “Elevation” from the menu. You will notice that the block will change accordingly to show the appropriate callout symbol. Similarly, you can click on the rotation grip and move it along the drawing area to change its rotation angle.