By Dennis Collin
Having a good library of blocks is vital for any organisation that needs to create good quality and consistent drawings. Not only do they save time in presenting professional documents but also can be scheduled using AutoCAD’s data extraction tools. In 2006 AutoCAD introduced Dynamic blocks which took the functionality of blocks further and enabled users to create clever, stretchable components which could automatically align themselves with elements such as pipework or wall elements.
I have previously posted about Dynamic Blocks here: Part 3
Another aspect of Dynamic blocks is the ability to define visibility states. This is a grouping within a block, like a layer where users can change the appearance of a block at an instance level.
However, the key difference is an object can be a member of many visibility states, whereas the same object can only reside on a single layer.
Consider a tree symbol, in a landscaping drawing. A user could create a tree block, but a typical project would have many different species of trees at different sizes. Instead of having multiple block definitions of each tree type, site variations can be accommodated within a single block, with a selectable drop down list provided to suit the actual trees properties and size etc.
To make the dynamic block, a collection of conventional blocks is collected into a single drawing. They are all drawn at a consistent size, (1 metre spread is a good default size) so that they can be uniquely scaled within the dynamic block environment (See Fig 1.) Create a new ‘Planting’ Block and select all the sub block components.
In the Block Editor, add a visibility state parameter. Create and name the visibility states to relate to the different symbolic representations i.e. Create a Shrub name for the shrub block etc.
Switch to each visibility state and then select the blocks that are not desired to display for that state and set them to Hide for Current State.
Once complete, test the block and ensure that the block displays correctly according to each visibility state setting, or tree type.
To enable the block to be different sizes, create a linear parameter and a corresponding Scale action to each block.
After adding the scale action, test the block. Each block can be set to a different type or species and have a unique spread. This can all be done from one block! I usually recommend when creating dynamic blocks to disable the Explode function!
Creating and managing dynamic blocks is just one of several topics that we cover on the 2-day AutoCAD Intermediate Course. However, we also provide focused days on just dynamic blocks. Visit https://training.cadline.co.uk where we will be happy to help.
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