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AdvancedFree AutoCAD course about 25 min

Dynamic blocks

A dynamic block changes shape or appearance through grips and lists: one door block that stretches from 720 to 920, flips and switches between single and double. Fewer blocks, fewer mistakes.

In this lesson you will

  • Explain parameters and actions
  • Add a stretch with value sets
  • Add flip and visibility states
  • Test and document dynamic blocks

Parameters and actions

In the Block Editor (BE), a parameter defines what can change — a distance, an angle, a flip line, a visibility list — and gives the block a grip. An action defines how geometry responds — stretch, move, scale, rotate, array, flip. Most behaviours are one parameter plus one action.

A single door block shown at three widths, 720, 820 and 920, controlled by a grip on a linear parameter, instead of three separate blocks.720820920one block · drag the grip or pick a width from a list
Figure: A dynamic block with a stretch parameter. Original KitWren diagram.

A stretchable door

  1. 1Open your door block in the Block Editor.
  2. 2Add a Linear parameter across the door width, from the hinge to the leading edge.
  3. 3In its Properties, set Dist type to List and add 720, 820, 920 — or Increment with a min and max.
  4. 4Add a Stretch action to the parameter: pick the end point, draw a crossing frame around the leading edge, and select the leaf and swing.
  5. 5For the swing arc, use a Scale action instead of stretch, or redraw the arc with a constraint.
  6. 6Save and close; select a reference and drag the grip — it snaps to the listed widths.

Test in the Block Editor with Test Block (BTESTBLOCK) before saving, so broken behaviours never reach the drawing.

Flip and rotation

Add a Flip parameter along the door's centreline with a Flip action on all geometry to swap handing with one click. Add a second flip across the wall for swing direction. A Rotation parameter and action lets furniture turn on a grip without the ROTATE command.

Visibility states

A Visibility parameter shows different sets of objects in named states: a Door block with states Single, Double and Sliding; a Toilet block with Plan and Elevation. In the Visibility States manager, create the states, then use Make Invisible to hide objects in each state. The reference gets a drop-down arrow to switch states.

Lookup tables and constraints

A Lookup parameter links several parameters to named sizes — e.g. choosing Queen bed sets width 1530 and length 2030. Full AutoCAD also supports geometric and dimensional constraints in the Block Editor with a Block Table of sizes, which is a cleaner way to build complex parametric blocks. Keep dynamic blocks simple enough that colleagues can maintain them.

Quick reference

Command / toolHow to start itWhat it does
BEDITBEBlock Editor with authoring palettes
BTESTBLOCKTest Block buttonTests a block before saving
BVSTATEVisibility States buttonManages visibility states
RESETBLOCKRight-click referenceResets a dynamic block to its default

Common mistakes

  • Stretch moves the whole block.

    The stretch frame must cross only the moving part, and the selection must include the objects to stretch.

  • Grip doesn't appear.

    The parameter has no action attached — add one.

Exercise

One door block to replace many

  1. Build a dynamic door with widths 720/820/920 via a linear list and stretch.
  2. Add two flip parameters for handing and swing side.
  3. Add visibility states Single and Double.
  4. Test it, save it, and replace three separate door blocks in your plan with it.

You should end up with: A single flexible door block.

Checklist

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Lesson quiz

1 / 4

In a dynamic block, what gives a block its grip?

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