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Ref. Issue #7 - 28 May 2008 - Creating and Using Dynamic Blocks

You probably have multiple similar blocks that you store and use on a regular basis. Moreover, you might insert these blocks at various scales and rotation angles. For example, you could have several sizes of doors that you insert at various angles, sometimes rightopening and sometimes left-opening. Dynamic blocks are blocks that contain intelligence and flexibility so that you can insert them in many variations. Potentially, you could significantly reduce the number of blocks in your block library.

Dynamic blocks let you specify the types and amounts of variations for each block. You create (author) dynamic blocks in the Block Editor. For a block to be dynamic, it must include at least one parameter. Each parameter usually has an associated action. Parameters define the special properties of the dynamic block, including locations, distances, and angles. Parameters can also constrain the values within which the parameter can function. An action specifies how a block uses its associated parameter to change in some way. For example, you may want to move one component of a block independently of the block, such as the chair in a block containing a desk and a chair. To accomplish this, you add a point parameter that specifies a point on the chair. You then add a move action that allows you to move the chair from that point.

Understanding the work flow of dynamic blocks
Because defining a dynamic block takes some time—although simpler dynamic blocks are not very time-consuming to set up—the most common use for dynamic blocks is to create a block library. Normally, you define your dynamic blocks and save them for future use in your drawings. In other words, unless you need to insert a new block many times in several variations in a drawing, you won’t create dynamic blocks for the current drawing on which you’re working.

A block library can have two configurations:

✦ One block per drawing: You save each block in its own drawing. Use the BASE command to specify the origin of the drawing, which is usually on an object snap somewhere on the block. You use the INSERT command to insert the drawing, thereby inserting its block.

✦ Many blocks per drawing: You put a number of (usually) related blocks in a drawing. To insert the block, you use the DesignCenter to locate the drawing and find the individual block that you want.
The first part of the process of creating dynamic blocks is to define the block.

1. In your block library drawing or in a new drawing, create the block.
2. Open the new Block Editor (the BEDIT command) and choose the block.
3. Add parameters and associated actions.
4. Save the block definition in the Block Editor.
5. Close the Block Editor.
6. If the drawing will contain just this block, use the BASE command to set the drawing
origin where you want the insertion point to be, usually somewhere on the block.
7. Save the drawing.

You may want to follow this process for any number of blocks. When your blocks are defined, you do the following to insert your dynamic blocks.

1. In your current drawing, either use the INSERT command to insert the drawing containing the block, or use the DesignCenter to choose the block from within the drawing.
2. Select the block to see its special grips. These grips show you where you can modify the block.
3. Usually, you click and drag a grip. Some dynamic block parameters involve choosing a visibility or lookup option.

Sometimes the parameter and action labels become too large. When this happens, click the Update Parameter and Action Text Size button on the Block Editor’s toolbar.

Sometimes, the parameter that you want to use has more grips than you need. For example, if you use a linear parameter, you end up with two grips, one at each end of the length that you define. However, you might want to stretch only in one direction; in this case, you need only one of the grips. To remove the extra grip, select the parameter, right-click, and choose Grip Display➪1. The other option is to use a point parameter with a stretch action.

Why would you use the linear parameter (instead of a point parameter) when you want to add a stretch action? When you stretch the inserted dynamic block, if you have Dynamic Input turned on, you see a linear tooltip that allows you to enter a total length. You can set the total length in the Properties palette, although that isn’t nearly as convenient. Also, a point parameter doesn’t offer the Value Set option, which lets you constrain sizes.

Source : AutoCAD2007 and AutoCAD2007 LT Bible by Ellen Finkelstein
Thanks to the source