BricsCAD: Creating Dynamic Annotation with Parametric Blocks (Part 1)

In this series of blog posts, we’ll discuss how you can use BricsCAD parametric blocks to create dynamic annotation. A parametric block is a type of block with special properties that, when adjusted, transform the geometry or presentation of the annotation or symbology represented. Akin to dynamic blocks in AutoCAD, parametric blocks take fewer steps to set up. The benefit of setting up parametric blocks is having one symbol that can adapt to varying displays without having to explode it to make it work.

Part 1: Adding a Stretch Parameter

Let’s look at creating an attributed section cut symbol with parametric. In the Block Editor, we have set up the basic geometry and attributes. By adding a stretch parameter, we want to stretch the tail of the section cut along its axis to accommodate variable spans.

Configuration of a block’s parametric properties is done on the 2D Parametric tab of the ribbon in the Block Editor.

To set up a stretch parameter, do the following:

1. From the Blocks panel of the 2D Parametric ribbon tab, click the bottom half of the Blocks button to display its options. Then click Stretch.
   
2. As the command line prompts, pick the base point of displacement. For this block, it would be where the horizontal line meets the edge of the circle.
3. Next, pick the second point of displacement which would be the opposite end of the line. Think of it as if you are measuring the length of the existing line.
4. Next, define a rectangle across the items that will stretch and include inside the rectangle the parts that will move with the stretch parameter. You do have the option of defining a polygon instead by entering P at the command line.
5. If you selected objects by mistake, you now are prompted to deselect those items. Hit enter when finished.
6. Next, as prompted, give the stretch parameter a name. This will be displayed in the Properties panel when the block is selected. For this block, we will name it Span.
7. Notice that in the Layers panel, a layer has been created names PARAMETRIC_STRETCH_VECTORS. The vector we just defined was created as a parametric line and placed in that layer.
   This layer is locked and may be turned off or frozen to prevent it’s display.

   This completes the setup of the stretch parameter. Next, we will test it.

8. Close the Block Editor by making the Block Editor ribbon tab current and clicking Save Block.
   
9. Insert the block anywhere in the drawing.
10. Click on the block and notice the Properties panel. There is a Parameters grouping at the bottom displaying the newly created Span parameter. The number value appearing next to it is showing the line’s current length.
    
11. Type in a larger value in the Span field to see the stretch parameter in action.
    

Notice that when the parameter’s value is changed, the pad lock icon next to it changes to the locked state which simply indicates that an override was made.

Using blocks with the stretch parameter enables the lengthening of a block when it must span wider or more narrow widths. This allows us to avoid exploding symbology to force annotation to work. We can also avoid creating and maintaining slightly varied duplicates of the block in our libraries which keeps our block libraries lean. Overall, parametric blocks help us to work smarter and efficiently.

Watch for Part 2 coming soon.

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